Lithium secondary battery and method for manufacturing same

Abstract

One embodiment provides a lithium secondary battery comprising: a positive electrode comprising a positive electrode current collector and a positive electrode mixture layer that is disposed on the positive electrode current collector and comprises a positive electrode active material and a sacrificial positive electrode active material; a negative electrode comprising a negative electrode current collector and a lithium host layer that is disposed on the negative electrode current collector and comprises a porous structure; and an electrolyte disposed between the positive electrode and the negative electrode, wherein, with respect to the lithium host layer, lithium is intercalated in an ionic state and plated in a metallic state, and the capacity of the sacrificial positive electrode active material is 10% to 70% of the total capacity of the positive electrode active material and the sacrificial positive electrode active material.

Description

Lithium secondary battery and method for manufacturing the same

[0001] The present disclosure relates to a lithium secondary battery and a method for manufacturing the same.

[0002] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material capable of lithium ion intercalation and deintercalation, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated from the positive electrode and the negative electrode.

[0003] Lithium metal batteries use lithium metal as the anode to provide high energy density, but problems arising during the lithium metal plating process can significantly affect battery performance. Lithium metal plating is the process in which lithium ions are reduced to lithium metal and precipitated on the surface of the anode during the charging process. Non-uniform lithium metal plating during this process can lead to dendrite formation, causing short circuits and safety issues in the battery. On the other hand, lithium ion insertion refers to the process in which lithium ions are inserted into and stored within the anode material of the battery.

[0004] The lithium host (Li-host) layer used as the negative electrode of a lithium metal battery may be a structure designed to safely accommodate and stabilize lithium metal. However, since the lithium host layer does not contain lithium in its initial state, the lithium required for the formation of the Solid Electrolyte Interphase (SEI) layer during formation must be supplied from other parts of the battery. Additionally, lithium may be consumed due to side reactions occurring within the lithium host layer.

[0005] In addition, the lithium electrodeposition inducing layer of a lithium metal battery serves to prevent the irregular deposition of lithium metal; for effective operation, a certain amount of lithium may need to be deposited or inserted into the electrodeposition inducing layer during the initial charging process. During this process, the electrodeposition inducing layer consumes a significant amount of lithium.

[0006] This results in significant lithium loss during initial cycles, which reduces the battery's available capacity and can lead to long-term performance degradation. Additionally, it may be difficult to achieve the theoretical energy density per unit volume and per unit weight of the designed battery.

[0007] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art.

[0008] The problem that the present invention aims to solve is to provide a lithium secondary battery and a method for manufacturing the same to solve the above-mentioned problems.

[0009] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below.

[0010] One embodiment provides a lithium secondary battery comprising a positive electrode including a positive current collector and a positive composite layer disposed on the positive current collector and comprising a positive active material and a sacrificial positive active material, a negative electrode including a negative current collector and a lithium host layer disposed on the negative current collector and comprising a porous structure, and an electrolyte disposed between the positive electrode and the negative electrode, wherein with respect to the lithium host layer, lithium is intercalated in an ionic state and lithium is plated in a metallic state, and the capacity of the sacrificial positive active material is 10% to 70% of the total capacity of the positive active material and the sacrificial positive active material.

[0011] Another embodiment provides a method for manufacturing a lithium secondary battery, comprising the steps of: preparing a positive electrode by placing a positive composite layer containing a positive active material and a sacrificial positive active material on a positive current collector; preparing a negative electrode by placing a lithium host layer containing a porous structure on a negative current collector; and placing an electrolyte between the positive electrode and the negative electrode, wherein the capacity of the sacrificial positive active material is 10% to 70% of the total capacity of the positive active material and the sacrificial positive active material, the porous structure includes pores in which lithium can be electrodeposited in a metallic state, the average porosity is 30% to 80%, the negative electrode capacity (N) is defined as the total discharge capacity by lithium intercalated in an ionic state within the lithium host layer and lithium plated in a metallic state on the upper surface of the lithium host layer and in the pores of the porous structure, the positive electrode capacity (P) is defined as the total capacity of the positive active material and the sacrificial positive active material, and the ratio of the negative electrode capacity (N) to the positive electrode capacity (P) is 0.5 to 1.5.

[0012] According to some embodiments of the present disclosure, lithium metal electrodeposition is performed on a lithium host layer to prevent the formation and growth of dendrites.

[0013] According to some embodiments of the present disclosure, the initial efficiency and lifespan characteristics of the battery can be improved by compensating for the initial lithium loss at the cathode through a sacrificial positive electrode active material.

[0014] According to some embodiments of the present disclosure, the theoretical energy density per volume and per weight of a pre-designed battery can be realized.

[0015] According to some embodiments of the present disclosure, a lithium electrodeposition-inducing layer derived from a sacrificial anode active material is formed, and the lifespan characteristics of a lithium secondary battery can be improved.

[0016] According to some embodiments of the present disclosure, a battery with excellent initial Coulomb efficiency and capacity retention rate can be designed by applying optimal values ​​for the capacity ratio of the sacrificial positive active material in the positive composite layer of a lithium metal battery including a lithium host layer in the negative electrode, the average porosity of the lithium host layer, and the ratio of the negative discharge capacity to the positive discharge capacity.

[0017] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below.

[0018] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0019] FIG. 1 is a drawing showing a stacked structure of a lithium secondary battery according to one embodiment of the present disclosure.

[0020] FIG. 2 is a schematic diagram showing the structure of a negative electrode before charging of a lithium secondary battery according to one embodiment.

[0021] FIG. 3 is a schematic diagram showing the structure of the negative electrode after charging of a lithium secondary battery according to one embodiment.

[0022] FIG. 4 is a flowchart illustrating a method for manufacturing a lithium secondary battery according to one embodiment of the present disclosure.

[0023] FIG. 5 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0024] FIG. 6 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0025] FIG. 7 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0026] FIG. 8 is a perspective view illustrating a lithium secondary battery according to one embodiment of the present disclosure.

[0027] FIG. 9 is an SEM image showing a cross-section of a positive electrode of a lithium secondary battery according to one embodiment of the present disclosure.

[0028] FIG. 10 is an SEM image showing a cross-section of a negative electrode of a lithium secondary battery according to one embodiment of the present disclosure.

[0029] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0030] Unless otherwise specifically stated in this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between.

[0031] Unless otherwise specified in this specification, a singular form may also include a plural form. Additionally, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0032] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0033] Methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, but suitable methods and materials are described herein. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0034] In this specification, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, components, materials, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, components, materials, or combinations thereof.

[0035] In this specification, the term “combination of these” means a mixture or combination with one or more of the described components, and may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0036] In this specification, the term “and / or” means any combination of one or more items described in relation and all combinations thereof. In this specification, the term “or” means “and / or”.

[0037] In this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is directly above the other part, but also cases where there is another part in between.

[0038] In this specification, terms such as "first," "second," etc., may be used to describe various components, but the components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another.

[0039] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0040] In this specification, "alloy" means a mixture of two or more metals.

[0041] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0042] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0043] In this specification, "lithiation" and "to lithiate" refer to the process of adding lithium to a positive electrode active material or a negative electrode active material.

[0044] In this specification, "delithiation" and "to delithiate" refer to the process of removing lithium from a positive electrode active material or a negative electrode active material.

[0045] In this specification, "charge" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0046] In this specification, "discharge" and "discharge" refer to the process of removing electrochemical energy from a battery.

[0047] In this specification, "anode" and "cathode" refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0048] In this specification, "cathode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0049]

[0050] Exemplary embodiments will be described in more detail below.

[0051] FIG. 1 is a diagram showing a stacked structure of a lithium secondary battery according to one embodiment of the present disclosure. FIG. 2 is a diagram schematically showing the structure of a negative electrode before charging of a lithium secondary battery according to one embodiment. FIG. 3 is a diagram schematically showing the structure of a negative electrode after charging of a lithium secondary battery according to one embodiment.

[0052] Referring to FIG. 1, a lithium secondary battery (100) according to one embodiment of the present disclosure may include a positive electrode (130), a negative electrode (160), and an electrolyte (170) disposed between the positive electrode (130) and the negative electrode (160). The positive electrode (130) may include a positive current collector (110) and a positive composite layer (120) disposed on the positive current collector (110). The negative electrode (160) may include a negative current collector (140) and a lithium host layer (150) disposed on the negative current collector (140). Accordingly, the electrolyte (170) may be disposed between the positive composite layer (120) and the lithium host layer (150).

[0053] positive current collector

[0054] The anode (130) includes an anode current collector (110). For example, the anode (130) can be prepared by forming an anode composite layer (120) on the anode current collector (110).

[0055] For example, the positive current collector (110) may include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0056] According to one embodiment, the positive current collector (110) may include aluminum (Al).

[0057] For example, the positive current collector (110) may include a base film and a metal substrate layer disposed on one or both sides of the base film, in the same way as the negative current collector (140) to be described later.

[0058]

[0059] Anode composite layer

[0060] A positive electrode composite layer (120) according to one embodiment may include a positive electrode active material and a sacrificial positive electrode active material. In the present disclosure, the positive electrode active material and the sacrificial positive electrode active material are different materials. In the present disclosure, "positive electrode active material" refers to a material that enables the charging and discharging of a battery through a process in which lithium ions are extracted from the positive electrode of a lithium secondary battery or lithium ions are inserted into the positive electrode. Such a material can operate the battery in a reversible manner in which lithium ions move to the negative electrode during charging and return to the positive electrode during discharging.

[0061] In contrast, the "sacrificial cathode active material" in this disclosure refers to an irreversible material that releases a large amount of lithium ions as it decomposes during the charging process of a lithium secondary battery and does not return to its original state after charging, and the lithium ions released in this process can be intentionally used to maintain the overall performance of the battery. Alternatively, it can serve to compensate for lithium loss occurring in the lithium metal electrodeposition inducing layer or other structures.

[0062] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used. The composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0063] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-b X b O 2-c D c(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Mn 2-b X b About 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b X c About 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni 1-b-c Mn b X c About 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2), Li a Ni b Co c L1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1), Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1), Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5), Li (3-f) Fe2(PO4)3(0≤f≤2), Li a FePO4(0.90≤a≤1.8).

[0064] In the chemical formula, A is Ni, Co, Mn, or a combination thereof; X 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; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L1 is Mn, Al, or a combination thereof.

[0065] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel cathode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0066] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 1:

[0067] <Chemical Formula 1>

[0068] Li a Ni x Co y M z O 2-b A b

[0069] In Chemical Formula 1, 1.0≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0≤y≤0.3, 0 <z≤0.3, x+y+z=1, M은 망간(Mn), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al) 및 보론(B)으로 이루어진 군으로부터 선택된 하나 이상이고, A는 F, S, Cl, Br 또는 이들의 조합이다.

[0070] In Chemical Formula 1, for example, 0.7≤x<1, 0 <y≤0.3, 0<z≤0.3, 0.8≤x<1, 0<y≤0.3, 0<z≤0.3, 0.8≤x<1, 0<y≤0.2, 0<z≤0.2, 0.83≤x<0.97, 0<y≤0.15, 0<z≤0.15, 또는 0.85≤x<0.95, 0<y≤0.1, 0<z≤0.1일 수 있다.

[0071] For example, the lithium transition metal oxide may be at least one of the compounds represented by the following chemical formulas 1-1 and 1-2:

[0072] <Chemical Formula 1-1>

[0073] LiNi x Co y Mn z O2

[0074] In Chemical Formula 1-1, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다.

[0075] <Chemical Formula 1-2>

[0076] LiNi x Co y Al z O2

[0077] In Chemical Formula 1-2, 0.6≤x≤0.95, 0 <y≤0.2, 0<z≤0.1이다. 예를 들어, 0.7≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.8≤x≤0.95, 0<y≤0.3, 0<z≤0.3이다. 예를 들어, 0.82≤x≤0.95, 0<y≤0.15, 0<z≤0.15이다. 예를 들어, 0.85≤x≤0.95, 0<y≤0.1, 0<z≤0.1이다.

[0078] For example, lithium transition metal oxides are LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04 O2, LiNi 0.8 Co 0.15 Mn 0.05O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.2 O2 or LiNi 0.88 Co 0.1 Al 0.02 It could be O2.

[0079] For example, the positive electrode active material may have a coating layer on the surface of a lithium transition metal oxide, or a mixture of a lithium transition metal oxide and a lithium transition metal oxide having a coating layer may be used.

[0080] For example, the coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element.

[0081] For example, the compound forming 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 mixtures thereof. For the coating layer formation process, any coating method may be used as long as the coating can be applied to the lithium transition metal oxide using the coating elements in a manner that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.).

[0082] In one embodiment, the anode composite layer (120) may further include an additive capable of acting as a sacrificial anode. This is referred to as a sacrificial anode active material in this disclosure, and according to one embodiment, the content of the sacrificial anode active material may be 10% to 15% by weight with respect to 100% by weight of the anode composite layer (120). The content of the anode active material may be 75% to 89% by weight with respect to 100% by weight of the anode composite layer (120).

[0083] In one embodiment, the sacrificial cathode active material may comprise any one of Li5FeO4, Li2MoO3, Li6CoO4, Li2O, Li3N, Li3P, or any combination thereof. Since such a material can release a large amount of lithium ions through a reduction reaction, it may have a relatively high charging capacity.

[0084] In the present disclosure, the charge capacity (or theoretical capacity) may refer to the maximum amount of charge that a positive electrode in a secondary battery can store lithium ions within a specific voltage range. The charge capacity can be calculated based on the number of electrons that can be emitted by a specific mass of positive electrode active material or sacrificial positive electrode active material reacting. The charge capacity can be controlled by adjusting the theoretical capacity by changing the type of sacrificial positive electrode active material or positive electrode active material, or by controlling it according to the degree of grinding of the active material.

[0085] For example, Li5FeO4 (hereinafter LFO) can have a high charge capacity of about 700 mAh / g.

[0086] In one embodiment, the anode composite layer (120) may further include a conductive material and a binder. For example, the anode composite layer (120) may include an anode active material, a sacrificial anode active material, a conductive material, and a binder. The content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the anode composite layer (120).

[0087] The binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0088] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0089] In the present disclosure, the lithium secondary battery may be a lithium metal battery in which the negative electrode active material layer is initially free, lithium metal derived from the positive electrode is electrodeposited upon charging, and the lithium metal is dissolved upon discharging.

[0090] In order to achieve a balanced high initial Coulomb efficiency, energy density, and capacity retention rate by considering the average porosity of the porous structure (154) in the lithium host layer to be described later or the ratio of the negative capacity to the positive capacity, the "capacity of the sacrificial positive active material" may be designed to have a specific ratio to the "total capacity of the positive active material and the sacrificial positive active material." Among the "total capacity of the positive active material and the sacrificial positive active material," the "capacity of the positive active material" may refer to the discharge capacity at discharge after the initial charge of the positive active material having a specific charge capacity that is controlled according to the loading amount. Among the "total capacity of the positive active material and the sacrificial positive active material," the "capacity of the sacrificial positive active material" may refer to the discharge capacity at discharge after the initial charge of the sacrificial positive active material having a specific theoretical charge capacity.

[0091] In one embodiment, the capacity ratio of the sacrificial cathode active material within the cathode, that is, the capacity of the sacrificial cathode active material, may be 10% to 70% of the total capacity of the cathode active material and the sacrificial cathode active material. Here, the capacity of the sacrificial cathode active material may refer to the charging capacity of the sacrificial cathode active material as described above. In addition, the total capacity of the cathode active material and the sacrificial cathode active material may refer to the sum of the discharge capacity after the initial charging of the cathode active material and the discharge capacity after the initial charging of the sacrificial cathode active material.

[0092] As another example, the capacity ratio of the sacrificial cathode active material in the cathode may be 10% to 65%, 10% to 60%, 10% to 55%, 10% to 50%, 10% to 45%, 10% to 40%, 10% to 35%, or 10% to 30%. Alternatively, the capacity ratio of the sacrificial cathode active material may be 30% to 70%, 30% to 65%, 30% to 60%, 30% to 55%, 30% to 50%, 30% to 45%, 30% to 40%, or 30% to 35%.

[0093] The capacity ratio of the sacrificial positive electrode active material is a value calculated by considering the weight of the sacrificial positive electrode active material among the positive electrode active material and the sacrificial positive electrode active material that serve as charge storage, and the theoretical capacity per unit weight according to the type of sacrificial positive electrode active material, unlike the content ratio of the sacrificial positive electrode active material within the positive electrode composite layer (120) which is the weight ratio occupied within the positive electrode composite layer (120).

[0094] When the ratio of the capacity of the sacrificial cathode active material has a capacity within the range described above regardless of the type of sacrificial cathode active material, a lithium metal battery with excellent energy density, performance, and lifespan characteristics can be manufactured under a specific average porosity of the lithium host layer and a specific ratio of the negative electrode capacity (N) to the positive electrode capacity (P).

[0095] cathode current collector

[0096] Referring to FIG. 2, the negative current collector (140) may not include a negative composite layer. Referring to FIG. 3, the negative current collector (140) that does not include a negative composite layer may have lithium metal deposited or plated on the negative current collector (140) by charging. The deposited lithium metal layer (300) may include plated lithium, lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, an organic compound containing lithium, or a combination thereof. The lithium metal layer (300) may include non-fibrous lithium, non-needle lithium, plate lithium, or any combination thereof. The lithium alloy contains lithium and a first metal, and the first metal may include indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0097] The material constituting the negative electrode current collector (140) can be any material that does not react with lithium, that is, a material that does not form an alloy or compound with lithium and has conductivity. The metal substrate is, for example, a metal or an alloy. The metal substrate may be, for example, made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The negative electrode current collector (140) may have a shape selected from, for example, a sheet, foil, film, plate, porous body, mesoporous body, through-hole containing body, polygonal ring body, mesh body, foam, and nonwoven body, but is not necessarily limited to these shapes and any shape used in the relevant technical field is possible.

[0098] The negative current collector (140) includes, for example, a first metal substrate. The first metal substrate includes the first metal as a main component or is made of the first metal. The content of the first metal included in the first metal substrate is, for example, 90 weight% or more, 95 weight% or more, 99 weight% or more, or 99.9 weight% or more with respect to the total weight of the first metal substrate. The first metal substrate may be composed of, for example, a material that does not react with lithium, that is, does not form an alloy and / or compound with lithium.

[0099] The first metal may be, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited to these; any metal used as a current collector in the relevant technical field may be used. The first metal substrate may be, for example, composed of one of the metals described above or composed of an alloy of two or more metals. The first metal substrate is, for example, in the form of a sheet or foil.

[0100] The negative current collector (140) may further include a coating layer (not shown) containing a second metal on a first metal substrate.

[0101] The negative current collector (140) may include, for example, a first metal substrate and a coating layer disposed on the first metal substrate and comprising a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer comprising the second metal is harder than the substrate comprising the first metal, deterioration of the first metal substrate can be prevented. The Mohs hardness of the material constituting the first metal substrate is, for example, 5.5 or less. The Mohs hardness of the first metal is, for example, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. The Mohs hardness of the first metal may be, for example, 2.0 to 6.0. The coating layer comprises the second metal. The coating layer may, for example, comprise the second metal as a main component or be composed of the second metal. The content of the second metal included in the coating layer is, for example, 90% by weight or more, 95% by weight or more, 99% by weight or more, or 99.9% by weight or more with respect to the total weight of the coating layer. The coating layer may be composed of, for example, a material that does not react with lithium, that is, does not form an alloy and / or compound with lithium. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or more. For example, the Mohs hardness of the second metal is 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, or 9.0 or more. The Mohs hardness of the second metal may be, for example, 6.0 to 12. If the Mohs hardness of the second metal is excessively low, it may be difficult to suppress the deterioration of the negative electrode current collector (140). If the Mohs hardness of the second metal is excessively high, processing may not be easy. The second metal is one or more selected from, for example, titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh).The coating layer may be composed of, for example, one of the metals described above, or an alloy of two or more metals. The difference in Mohs hardness between the first metal included in the first metal substrate and the second metal included in the coating layer may be, for example, 2 or more, 2.5 or more, 3 or more, 3.5 or more, or 4 or more. By having such a difference in Mohs hardness between the first metal and the second metal, the deterioration of the negative current collector (140) can be suppressed more effectively. The coating layer may be a single-layer structure or a multilayer structure of two or more layers. The coating layer may be a two-layer structure including, for example, a first coating layer and a second coating layer. The coating layer may be a three-layer structure including, for example, a first coating layer, a second coating layer, and a third coating layer. The thickness of the coating layer may be, for example, 10 nm to 1 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm. The coating layer may be deposited on the first metal substrate by, for example, vacuum deposition, sputtering, plating, etc., but is not necessarily limited to these methods; any method capable of forming a coating layer in the relevant technical field is possible.

[0102] The negative current collector (140) may have a shape selected from, for example, a sheet, foil, film, plate, porous body, mesoporous body, through-hole containing body, polygonal ring body, mesh body, foam, and nonwoven body, but is not necessarily limited to these shapes and any shape used in the relevant technical field is possible.

[0103] The negative current collector (140) may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. The negative current collector may have a structure comprising a substrate, wherein the substrate may include, for example, a base film and a metal substrate layer disposed on one or both sides of the base film. An intermediate layer may be additionally disposed on the metal substrate layer.

[0104] For example, the base film may include a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. By including a thermoplastic polymer in the base film, the base film may melt upon the occurrence of a short circuit, thereby suppressing a sudden increase in current. The base film may be, for example, an insulator.

[0105] The metal substrate layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The metal substrate layer can act as an electrochemical fuse and cut off upon overcurrent to perform a short-circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal substrate layer. The metal substrate layer may be plated or deposited on a base film. As the thickness of the metal substrate layer decreases, the limit current and / or maximum current of the negative electrode current collector decreases, thereby improving the stability of the lithium metal secondary battery during a short circuit.

[0106] A lead tab may be added to the metal substrate layer for external connection. The lead tab may be welded to the metal substrate layer or the metal substrate layer / base film laminate by means of ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal substrate layer may melt, thereby electrically connecting the metal substrate layer to the lead tab. To make the weld between the metal substrate layer and the lead tab more robust, a metal chip may be added between the metal substrate layer and the lead tab. The metal chip may be a thin sheet of the same material as the metal of the metal substrate layer. The metal chip may be, for example, metal foil, metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to the metal chip / metal substrate layer laminate or the metal chip / metal substrate layer / base film laminate by placing the metal chip on the metal substrate layer and then welding it to the lead tab. During welding, the base film, metal layer, and / or metal chip may melt, allowing the metal layer or the metal layer / metal chip laminate to be electrically connected to the lead tab. A metal chip and / or lead tab may be added to a portion of the metal substrate layer. The thickness of the base film may be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. By having the base film within this thickness range, the weight of the cathode assembly can be reduced more effectively. The melting point of the base film may be, for example, 100 to 300 °C, 100 to 250 °C, or 100 to 200 °C. By having the base film within this melting point range, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. Surface treatments, such as corona treatment, may be performed on the base film to improve the adhesion between the base film and the metal substrate layer. The thickness of the metal substrate layer is, for example, 0.The thickness may be 0.1 μm to 3 μm, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 1 μm. By having a thickness within this range, the stability of the cathode can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 μm to 10 μm, 2 μm to 7 μm, or 4 μm to 6 μm. By having a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having the cathode current collector with this structure, the weight of the electrode can be reduced and, consequently, the energy density can be improved.

[0107] According to one embodiment, a negative active material layer may be free on the negative current collector (140) before charging and discharging. For example, a lithium metal layer (300) may be free on the negative current collector (140) before charging and discharging.

[0108] According to one embodiment, the cathode may further include an interlayer disposed between the cathode current collector (140) and the lithium metal layer (300).

[0109] According to one embodiment, although not illustrated, an interlayer may be placed directly on one or both sides of, for example, the negative current collector (140). Thus, no other layer may be placed between the negative current collector (140) and the interlayer. By placing the interlayer directly on one or both sides of the negative current collector (140), the bonding strength between the negative current collector (140) and the lithium metal layer (300) may be further improved.

[0110] The thickness of the intermediate layer may be, for example, 30% or less of the thickness of the negative current collector (140). The thickness of the intermediate layer is, for example, 0.01 to 30%, 0.1 to 30%, 0.5 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, 1 to 5%, or 1 to 3% of the thickness of the negative current collector (140). The thickness of the intermediate layer is, for example, 10 nm to 5 µm, 50 nm to 5 µm, 200 nm to 4 µm, 500 nm to 3 µm, 500 nm to 2 µm, 500 nm to 1.5 µm, or 700 nm to 1.3 µm.

[0111] By having the intermediate layer have a thickness within this range, the bonding strength between the negative current collector (140) and the lithium metal layer (300) is further improved, and the increase in interfacial resistance can be suppressed.

[0112] For example, the intermediate layer may include a binder. By including a binder in the intermediate layer, the bonding strength between the negative current collector (140) and the lithium metal layer (300) can be further improved. The binder included in the intermediate layer is, for example, a conductive binder or a non-conductive binder.

[0113] Conductive binders are, for example, ion-conducting binders and / or electronic-conducting binders. Binders that possess both ion conductivity and electronic conductivity may belong to both ion-conducting binders and electronic-conducting binders.

[0114] Ion-conducting binders are, for example, polystyrene sulfonate (PSS), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), poly(methylmethacrylate) (PMMA), polyethylene oxide (PEO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, and polyacetylene. Ion-conducting binders may include polar functional groups. Ion-conducting binders containing polar functional groups are, for example, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi+ etc.The electronically conductive binder is, for example, polyacetylene, polythiophene, polypyrrole, poly(p-phenylene), poly(phenylenevinylene), poly(phenylenesulfide), polyaniline, etc. The intermediate layer may be, for example, a conductive layer containing a conductive polymer.

[0115] The binder included in the intermediate layer may be, for example, a fluorine-based binder. The fluorine-based binder included in the intermediate layer may be, for example, polyvinylidene fluoride (PVDF). The intermediate layer may be disposed on the cathode current collector, for example, dry or wet. The intermediate layer may be, for example, a binding layer containing a binder.

[0116] The intermediate layer may additionally include, for example, a carbon-based conductive material. By including the carbon-based conductive material, the intermediate layer may be, for example, a conductive layer. The intermediate layer may be, for example, a conductive layer including a binder and a carbon-based conductive material.

[0117] The intermediate layer may be disposed on the cathode current collector (140) in a dry manner by deposition, for example, CVD, PVD, etc. The intermediate layer may be disposed on the cathode current collector in a wet manner by, for example, spin coating, dip coating, etc. The intermediate layer may be disposed on the cathode current collector (140) by, for example, depositing a carbon-based conductive material on the cathode current collector (140) by deposition. The dry-coated intermediate layer may be made of a carbon-based conductive material and may not contain a binder. Alternatively, the intermediate layer may be disposed on the cathode current collector (140) by, for example, coating a composition comprising a carbon-based conductive material, a binder, and a solvent on the surface of the cathode current collector (140) and drying it. The intermediate layer may have a single-layer structure or a multi-layer structure including multiple layers.

[0118] lithium host layer

[0119] In a lithium metal battery, the lithium host layer of the negative electrode can effectively manage the storage and release of lithium ions to alleviate volume expansion of the battery and suppress dendrite formation, thereby improving the safety and lifespan characteristics of the battery.

[0120] FIG. 2 shows a simplified structure of the lithium host layer (150) of the cathode (160) for convenience of explanation, but the structure is not limited thereto. Referring to FIG. 2, the lithium host layer (150) according to one embodiment may include a porous structure (154). In the lithium host layer (150), lithium may be intercalated in an ionic state and lithium may be plated in a metallic state. The porous structure (154) may include pores (152). Here, the pores (152) may be pores (152) of a size in which lithium can be plated in a metallic state. The interior of the porous structure (154), excluding the pores (152), may have lithium intercalated in an ionic state. The lithium host layer (150) according to one embodiment may be designed as a hybrid lithium host layer in which the intercalation and plated mechanisms can proceed simultaneously.

[0121] A lithium host layer (150) according to one embodiment of the present disclosure may not contain lithium. For example, the lithium host layer (150) may include any one of graphite, hard carbon, carbon nanotubes (CNT), graphene, silicon-carbon composites, carbon nanofibers (CNF), or any combination thereof. However, it is not limited thereto, and various materials that do not contain lithium and in which the lithium intercalation mechanism can occur may be adopted.

[0122] In one embodiment, the lithium host layer (150) may be made of a carbon-metal composite material. For example, a composite of carbon nanotubes and metal nanoparticles may be used. Here, the carbon nanotubes allow for the insertion of lithium ions, and the metal nanoparticles can promote the uniform electrodeposition of lithium metal. Specifically, after lithium ions are inserted into the inner wall of the carbon nanotubes, they can be uniformly electrodeposited on the surface.

[0123] In one embodiment, the lithium host layer (150) may be made of a TiO2-based composite material. For example, TiO2 nanotubes / TiO2 nanoparticles may be used. TiO2 can be inserted with lithium ions and simultaneously serve as a substrate for lithium metal electrodeposition. Depending on the surface area and structure of TiO2, both lithium insertion and electrodeposition can occur effectively. Specifically, in a TiO2 nanotube structure, the process of lithium ions being inserted into the tube and then electrodeposited on the outer surface can occur.

[0124] In one embodiment, the lithium host layer may further include a conductive material and a binder.

[0125] The binder serves to adhere the components of the lithium host layer (150) well to each other and also adheres the components of the lithium host layer (150) well to the negative current collector (140). As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0126] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or combinations thereof.

[0127] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0128] When using a water-based binder as the cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be used in a mixture. Na, K, or Li may be used as the alkali metal.

[0129] The dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0130] A conductive material is used to impart conductivity to an electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives or mixtures thereof.

[0131] A lithium host layer (150) according to one embodiment includes a porous structure (154), and the porous structure (154) may include pores (152) in which lithium can be electrodeposited in a metallic state. The shape of the pores (152) may be irregular. The average porosity of the porous structure (154) is defined by the following Equation 1.

[0132] [Equation 1]

[0133] Average Porosity (%) = [(Area of ​​Lithium Host Layer × Thickness of Lithium Host Layer) - (Weight of Lithium Host Layer Constituent Material × Ratio of Constituent Material / Total Density of Constituent Material)] / [Area of ​​Lithium Host Layer × Thickness of Lithium Host Layer] × 100

[0134] If the average porosity of the lithium host layer (150) of a lithium metal battery is excessively high, the mechanical strength may be weakened, and if the average porosity is excessively low, the movement of lithium ions may be restricted. Therefore, the average porosity can be adjusted to an optimal level to produce a lithium metal battery with excellent energy density, performance, and lifespan characteristics. There may be various methods for adjusting the average porosity of the lithium host layer (150).

[0135] For example, the porosity of nanowires, nanotubes, or nanosheet structures used in the synthesis of 3D nanostructures can be controlled. Alternatively, the porosity can be controlled during the aerogel synthesis process.

[0136] As another example, the size and distribution of pores can be controlled by adjusting the precursor concentration, pH, and temperature using a sol-gel process that synthesizes solid-state materials from liquid precursors. Alternatively, porosity can be controlled by adjusting the voltage and current density while depositing metal or carbon-based nanostructures using an electrochemical deposition method.

[0137] In one embodiment, the porous structure (154) comprises pores (152) of a size in which lithium can be electrodeposited in a metallic state, and the above-described average porosity may be 30% to 80% or 50% to 70%. The average porosity may be, for example, 50% to 65%, 50% to 60%, or 50% to 55%. Or, the average porosity may be 55% to 70%, 60% to 70%, or 65% to 70%.

[0138] When the pores of the lithium host layer have an average porosity within the range described above regardless of the composition of the lithium host layer, a lithium metal battery with excellent energy density, performance, and lifespan characteristics can be manufactured under a specific ratio of the capacity of the sacrificial cathode active material in the cathode composite layer or a specific ratio of the negative electrode capacity (N) to the positive electrode capacity (P).

[0139] lithium metal layer

[0140] Referring to FIGS. 1 and 3, the lithium secondary battery (100) may further include a lithium metal layer (300) disposed between a negative electrode current collector (140) and an electrolyte (170). The lithium metal layer (300) may be a lithium electrodeposited layer formed as charging and discharging progresses, which was initially free of the battery. The lithium metal layer (300) may include lithium metal or a lithium alloy. The lithium metal layer (300) may function as a negative electrode active material layer.

[0141] For example, the lithium metal layer (300) may be formed as lithium ions contained in the electrolyte (170) are electrodeposited onto the negative electrode current collector (140) as the lithium secondary battery (100) is charged. The lithium ions contained in the electrolyte (170) may originate from the positive active material or the sacrificial positive active material of the positive electrode (130) depending on the charging and discharging process. The lithium ions contained in the electrolyte (170) may be generated by the oxidation of the positive active material or the sacrificial positive active material during the battery charging process. For example, the lithium metal layer (300) may include a lithium alloy and a lithium metal. For example, the lithium alloy contained in the lithium metal layer (300) may weaken the reactivity of the lithium metal, thereby effectively preventing side reactions between the lithium metal layer (300) and the electrolyte (170). Additionally, the lithium metal layer (300) has excellent electrical conductivity, which may reduce the internal resistance of the lithium secondary battery (100) containing it. Accordingly, the lithium secondary battery (100) including the lithium metal layer (300) can have improved lifespan characteristics as well as charge / discharge efficiency.

[0142] According to one embodiment, the lithium metal layer (300) may comprise only electrodeposited lithium metal or lithium alloy. In this case, the lithium metal layer (300) may be a lithium electrodeposited layer.

[0143] According to one embodiment, the lithium metal layer may not include a carbon-based negative electrode active material. Accordingly, the lithium metal layer may be composed of a metal-based negative electrode active material.

[0144] Referring to FIG. 3, the lithium metal layer (300) may be formed by electrodepositing some of the lithium derived from the positive electrode composite layer (e.g., 120 in FIG. 1) into the pores (152) of the porous structure (e.g., 154 in FIG. 2) or on the upper surface of the lithium host layer (150). Here, the upper surface of the lithium host layer (150) may refer to the uppermost surface of the porous structure. For example, referring to FIG. 1, the upper surface of the lithium host layer (150) may refer to the interface between the porous structure and the electrolyte (170). Some of the lithium derived from the positive electrode composite layer may be inserted into the porous structure of the lithium host layer (150) itself in the form of lithium ions. In one embodiment, the discharge capacity (mAh / g) of the negative electrode (160) may include a small amount of lithium metal electrodeposited on the upper part of the lithium host layer (150), lithium ions inserted into the porous structure, and a discharge capacity stored in the lithium metal electrodeposited in the pores of the porous structure.

[0145] electrolytes

[0146] The electrolyte (170) can be, for example, a liquid electrolyte, a solid electrolyte, or a gel electrolyte.

[0147] The electrolyte (170) is, for example, an organic electrolyte. The organic electrolyte is prepared, for example, by dissolving a lithium salt in an organic solvent. Any organic solvent used as an organic solvent in the relevant technical field may be used. Organic solvents are, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

[0148] Any lithium salt used as a lithium salt in the relevant technical field is also acceptable. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1 The lithium salts are SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI, or mixtures thereof. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M.

[0149] The electrolyte (170) according to one embodiment may be a solid electrolyte. The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymeric solid electrolyte, or a combination thereof.

[0150] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 It is one or more selected from (M = Te, Nb, or Zr, where x is an integer from 1 to 10). Solid electrolytes are produced by sintering methods, etc. For example, oxide-based solid electrolytes include Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a MaO 12 It is a garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0151] Sulfide-based solid electrolytes may comprise, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or combinations thereof. Sulfide-based solid electrolyte particles may comprise Li2S, P2S5, SiS2, GeS2, B2S3, or combinations thereof. Sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles have high lithium ion conductivity compared to other inorganic compounds. For example, sulfide-based solid electrolytes comprise Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte comprises Li2S-P2S5, the mixed molar ratio of Li2S to P2S5 may be, for example, in the range of about 50:50 to about 90:10. Additionally, Li3PO4, halogens, halogen compounds, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x ("LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75An inorganic solid electrolyte prepared by adding S4 ("ThioLISICON"), Li2O-Al2O3-TiO2-P2O5 ("LATP"), etc., to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5, Li2S-P2S5-LiX (X = halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다.

[0152] In addition, a calcination process may be performed after the above treatment. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof.

[0153] The electrolyte (170) may be a polymeric solid electrolyte. A polymeric solid electrolyte is, for example, an electrolyte containing a mixture of a lithium salt and a polymer, or an electrolyte containing a polymer having an ion-conducting functional group. A polymeric solid electrolyte is, for example, a polymeric electrolyte that does not contain a liquid electrolyte.The polymers included in the polymeric solid electrolyte are, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methylmethacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, Polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, Sulfonated poly, (ether ether ketone) (sulfonated poly(ether ether ketone), SPEEK), Sulfonated poly(arylene ether ketone ketone sulfone) (sulfonated poly(aryl ether ketone, SPAEK), Poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), Polystyrene sulfonate (Poly(styrene sulfonate), PSS), Lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +It may be ) or a combination thereof, but is not limited thereto, and any that are used as polymer electrolytes in the relevant technical field are permitted. Any lithium salt that can be used as a lithium salt in the relevant technical field is permitted. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(x and y are each 1 to 20), LiCl, LiI, or mixtures thereof, etc.

[0154] The electrolyte (170) according to one embodiment may be a gel electrolyte. The gel electrolyte is, for example, a gel polymer electrolyte. The gel polymer electrolyte is, for example, an electrolyte comprising a liquid electrolyte and a polymer, or comprising an organic solvent and a polymer having an ion-conducting functional group. The liquid electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer may be selected from among polymers used in solid polymer electrolytes. The organic solvent may be selected from among organic solvents used in liquid electrolytes. The lithium salt may be selected from among lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt in a liquid state at room temperature or a room temperature molten salt that has a melting point below room temperature and consists only of ions. The ionic liquid comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 -, HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include one or more compounds selected from those containing one or more anions selected from among. A gel polymer electrolyte may be formed by impregnating the polymer solid electrolyte into the electrolyte in a lithium secondary battery. In addition, the gel electrolyte may further include inorganic particles.

[0155] separator

[0156] A lithium secondary battery (100) according to one embodiment may further include a separator (not shown).

[0157] As a separator, polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof may be used, and of course, mixed multilayer films such as polyethylene / polypropylene two-layer separator, polyethylene / polypropylene / polyethylene three-layer separator, polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0158] The separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0159] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0160] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0161] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0162] Organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0163] lithium secondary battery

[0164] Referring to FIGS. 1 to 3, in a lithium secondary battery (100) according to one embodiment, a lithium metal layer (300) derived from an anode composite layer (120) may be formed on the pores (152) of a porous structure (154) and on the upper surface of a lithium host layer (150). Additionally, lithium derived from a sacrificial anode active material may be included in the SEI layer formed on the surface of the porous structure (154).

[0165] In one embodiment, the lithium host layer (150) does not contain lithium, so a large amount of lithium is consumed in the formation of the SEI layer during the formation process, making it difficult to achieve the theoretical energy density per volume and per weight of the designed lithium secondary battery (100). This may be because the lithium contained in the SEI layer formed by the reaction of lithium ions with the electrolyte (170) is not released again during the charge-discharge cycle of the battery.

[0166] However, by including lithium derived from the sacrificial positive active material in the SEI layer formed on the surface of the porous structure (154), the amount of lithium from the positive active material consumed in the formation of the SEI layer can be reduced. Under a specific average porosity of the lithium host layer (150), the SEI layer can be formed in the lower pores (152) of the lithium host layer (150). The SEI layer can improve the lifespan and safety of the battery by suppressing side reactions between the electrolyte (170) passing through the pores (152) and the electrode material while maintaining the permeability of lithium ions. Since the SEI layer is lithium-friendly, it can contribute to ensuring that the lithium metal layer (300) is uniformly electrodeposited from the bottom within the lithium host layer (150) by the SEI layer formed in the lower pores (152) of the lithium host layer (150). Accordingly, uneven electrodeposition of the lithium metal layer (300) can be prevented, and the negative electrode volume expansion mitigation function of the lithium host layer (150) can be maximized.

[0167] In one embodiment, a lithium electrodeposition inducing layer (not shown) may be further included within the lithium host layer (150). The lithium electrodeposition inducing layer may be included within the lithium host layer (150) of the lithium secondary battery (100) before performing charge and discharge. The lithium electrodeposition inducing layer may play an important role in helping the lithium metal layer (300) derived from the positive electrode composite layer (120) to be evenly distributed in the pores (152) of the porous structure (154), thereby enabling the lithium metal to grow evenly during battery charging.

[0168] As a component of the lithium electrodeposition inducing layer, graphene, carbon nanotubes, mesoporous carbon, metal nanoparticles, metal composites, polyethylene oxide (PEO), conductive polymers, titanium oxide (TiO2), ceria (CeO2) or conductive oxides, graphene metal composites, CNT-metal oxide composites, etc. may be adopted, but are not limited thereto, and any material capable of promoting the movement of lithium ions and inducing uniform electrodeposition of lithium metal may be used.

[0169] In one embodiment, if a lithium electrodeposition inducing layer is further included within the lithium host layer (150), the capacity of the positive electrode active material may be irreversibly consumed by the aforementioned lithium electrodeposition inducing layer. This is because when lithium reacts with the components of the lithium electrodeposition inducing layer to form a lithium compound, this compound often exists in a stable and inert state. For example, if lithium reacts with an oxide such as TiO2 to form a lithium compound such as Li2O, the lithium is not re-ionized and released. Such lithium cannot participate again in the electrochemical process of the battery and can be considered to be irreversibly lost.

[0170] In the charging process of a lithium secondary battery (100), if lithium is non-uniformly deposited due to various factors and dendrites grow or the grown dendrites detach from the electrode (this is called dead lithium (dead-Li)), the lithium included in this structure cannot be used during the discharge process and is excluded from the available lithium of the battery.

[0171] Due to the technical problems described above, the initial Coulomb efficiency may be reduced and long-term life characteristics may be degraded. To compensate for initial irreversible losses and to improve the initial charge / discharge capacity and performance of the battery, a prelithiation method may be used. For example, a method of introducing a lithium metal sheet or powder into the lithium host layer (150), or a method of adding a lithium-containing alloy (e.g., Li-Si alloy) or compound (e.g., lithium oxide) to the lithium host layer (150) may be used. However, these methods may result in a very complex process for uniform distribution of lithium and cause a significant increase in costs.

[0172] Therefore, to solve the aforementioned problems, a sacrificial cathode active material is introduced to compensate for the lithium lost due to irreversible reactions with the lithium electrodeposition inducing layer, SEI layer formation, dendrite formation, and side reactions in the lithium host layer (150). Since the sacrificial cathode active material is added to the cathode active material, the general secondary battery electrode plate process can be maintained. For example, by adding a portion of LFO to the cathode, the lithium consumed by side reactions occurring in the lithium host layer (150), SEI layer formation, and the lithium electrodeposition inducing layer during the formation stage can be supplied from the LFO. Additionally, the lithium supplied from the LFO can be utilized as a lithium electrodeposition site, etc., during the charging process.

[0173] For example, when charging a lithium secondary battery (100) to about 4.5 V, an irreversible charging capacity is generated by the phase transition of the LFO, allowing the battery to operate partially, and at the same time, excess lithium is provided to the negative electrode (160) to compensate for the aforementioned lithium consumption. The excess lithium provided to the negative electrode can compensate for the irreversible capacity of the negative electrode (160) caused by SEI layer formation, dendrite growth, and dead lithium occurring during initial formation and charging / discharging. In addition, the excess lithium provided to the negative electrode (160) can increase lithium affinity to induce lithium electrodeposition, thereby more effectively improving the lifespan characteristics of the lithium secondary battery (100). Furthermore, an optimal composition having a combination of the ratio of the capacity of the sacrificial cathode active material to the total capacity of the positive active material and the sacrificial cathode active material, and the ratio of the negative electrode capacity (N) to the positive capacity (P), which is effective for these lifespan characteristics and initial Coulomb efficiency, can be introduced into the electrode.

[0174] In one embodiment, when the content of the sacrificial cathode active material is sufficient to compensate for lost lithium, or the capacity ratio of the sacrificial cathode active material to the total capacity of the cathode active material and the sacrificial cathode active material has a specific value, the average porosity of the porous structure of the lithium host layer (150) is designed to be within a specific range, thereby enabling the manufacture of a lithium secondary battery (100) with excellent energy density, lifespan characteristics, and performance.

[0175] Meanwhile, in one embodiment, the ratio of the negative capacity (N) to the positive capacity (P) may be designed to be 0.6 to 0.9. Alternatively, if the average porosity of the porous structure of the lithium host layer (150) described above or the ratio of the capacity of the sacrificial positive active material to the total capacity of the positive active material and the sacrificial positive active material has a specific value, the ratio of the negative capacity (N) to the positive capacity (P) may be designed to be 0.5 to 1.5, or 0.6 to 1.0.

[0176] Here, the negative electrode capacity (N) is defined as the total discharge capacity due to lithium intercalated in an ionic state within the lithium host layer (150) and lithium plated in a metallic state on the upper surface of the lithium host layer (150) and in the pores (152) of the porous structure (154), and the positive electrode capacity (P) is defined as the discharge capacity after initial charging due to the positive electrode active material and the sacrificial positive electrode active material.

[0177] In the present disclosure, discharge capacity is the amount of electrical energy that a negative electrode active material can release during the discharge process in a secondary battery, and may refer to the amount of charge generated when the negative electrode active material discharges a constant current. Discharge capacity can be defined by the following Equation 2.

[0178] [Equation 2]

[0179] Discharge capacity (mAh / g) = (Discharge current (mA)) × (Discharge time (h)) / (Total mass of lithium host layer and electrodeposited lithium metal layer (g))

[0180] For example, the ratio of the cathode capacity (N) to the anode capacity (P) may be 0.6 to 0.9, 0.6 to 0.8, 0.6 to 0.75, 0.6 to 0.7, or 0.6 to 0.65. Alternatively, the ratio of the cathode capacity (N) to the anode capacity (P) may be 0.65 to 1.0, 0.7 to 1.0, 0.75 to 1.0, 0.8 to 1.0, or 0.85 to 1.0. Alternatively, the ratio of the cathode capacity (N) to the anode capacity (P) may be 1.0 to 1.3, 1.0 to 1.2, 1.0 to 1.1, 1.2 to 1.4, 1.2 to 1.5, or 1.3 to 1.5.

[0181] When the average porosity of the porous structure (154) of the lithium host layer (150) and / or the ratio of the capacity of the sacrificial cathode active material to the total capacity of the positive active material and the sacrificial cathode active material corresponds to the range described above, and when the ratio of the negative capacity (N) to the positive capacity (P) also corresponds to the range described above, a battery with excellent energy density, performance, and lifespan characteristics can be manufactured.

[0182] Some examples of the optimal combination of the average porosity of a porous structure (154) capable of designing a lithium metal battery with excellent energy density, performance, and lifespan characteristics, the capacity ratio of the sacrificial cathode active material to the total capacity of the positive active material and the sacrificial cathode active material, or the ratio of the negative capacity (N) to the positive capacity (P) are as follows.

[0183] In one embodiment, the capacity of the sacrificial cathode active material is 10% to 70% of the total capacity of the cathode active material and the sacrificial cathode active material, and the average porosity of the porous structure (154) may be 50% to 70%.

[0184] In one embodiment, the capacity of the sacrificial cathode active material is 10% to 70% of the total capacity of the cathode active material and the sacrificial cathode active material, and the ratio of the negative capacity (N) to the positive capacity (P) may be 0.6 to 0.9.

[0185] In one embodiment, the average porosity of the porous structure (154) is 50% to 70%, and the ratio of the cathodic capacity (N) to the anode capacity (P) may be 0.5 to 1.5.

[0186] In one embodiment, the capacity of the sacrificial positive electrode active material is 10% to 70% of the total capacity of the positive electrode active material and the sacrificial positive electrode active material, the average porosity of the porous structure (154) is 40% to 70%, and the ratio of the negative electrode capacity (N) to the positive electrode capacity (P) may be 0.5 to 1.5.

[0187] In one embodiment, the capacity of the sacrificial positive electrode active material is 10% to 50% of the total capacity of the positive electrode active material and the sacrificial positive electrode active material, the average porosity of the porous structure (154) is 50% to 70%, and the ratio of the negative electrode capacity (N) to the positive electrode capacity (P) may be 0.5 to 1.5.

[0188] Method for manufacturing a lithium secondary battery

[0189] FIG. 4 is a flowchart illustrating a method for manufacturing a lithium secondary battery according to one embodiment of the present disclosure. Techniques that overlap with the above description will be omitted.

[0190] A method for manufacturing a lithium secondary battery according to one embodiment of the present disclosure may include the step of preparing a positive electrode by placing a positive composite layer comprising a positive active material and a sacrificial positive active material on a positive current collector (S400), the step of preparing a negative electrode by placing a lithium host layer comprising a porous structure on a negative current collector (S410), and the step of placing an electrolyte between the positive electrode and the negative electrode (S420).

[0191] In the step (S400) of preparing a positive electrode by placing a positive electrode composite layer containing a positive electrode active material and a sacrificial positive electrode active material on a positive electrode current collector, a mixture of the positive electrode active material and the sacrificial positive electrode active material, a conductive material, and a binder may be mixed in a weight ratio of 90:5:5 and coated onto a positive electrode current collector such as an aluminum (Al) substrate, followed by drying and rolling. The weight ratio is not limited to 90:5:5, and any weight ratio generally known in the art to manufacture a positive electrode composite layer for a lithium secondary battery may be possible.

[0192] In the step (S410) of preparing a negative electrode by placing a lithium host layer containing a porous structure on a negative electrode current collector, a precursor composition of the lithium host layer, a conductive material, and a binder may be mixed in a weight ratio of 90:5:5 and coated onto a negative electrode current collector, such as a copper (Cu) substrate, followed by drying and rolling. The weight ratio is not limited to 90:5:5, and any weight ratio generally known in the art to manufacture a negative electrode composite layer of a lithium secondary battery may be possible.

[0193] The flowchart of FIG. 4 and the description above are merely examples of the present disclosure, and the scope of the present disclosure is not limited to the flowchart of FIG. 4 and the description above. For example, one or more steps in the flowchart and the description above may be added, changed, or deleted, the order of one or more steps may be changed, and one or more steps may be performed simultaneously.

[0194] FIGS. 5 to 8 are perspective views illustrating a lithium secondary battery according to an embodiment of the present disclosure. FIG. 5 is cylindrical, FIG. 6 is prismatic, and FIGS. 7 and 8 are pouch-type batteries. Referring to FIGS. 5 to 8, the lithium secondary battery (1) includes a battery structure (7, electrode assembly) having a separator (4, separator) interposed between a positive electrode (3) and a negative electrode (2), and a case (5) in which the battery structure (7) is housed. The positive electrode (3), the negative electrode (2), and the separator (4) may be impregnated with an electrolyte (not shown). The lithium secondary battery (1) may include an assembly (6, sealing member) that seals the case (5) as in FIG. 5. Additionally, in FIG. 6, the lithium secondary battery (1) may include a positive lead tab (3') and a positive terminal (3"), a negative lead tab (2') and a negative terminal (2"). As shown in FIGS. 7 and 8, the lithium secondary battery (1) may include electrode tabs (70), namely a positive electrode tab (71) and a negative electrode tab (72), which serve as electrical passages for inducing current formed in the battery structure (7) to the outside.

[0195] Referring to FIG. 5, a lithium secondary battery (1) according to one embodiment includes the anode (3), the cathode (2), and the separator (4) described above. The anode (3), the cathode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is housed in a case (5). An electrolyte is injected into the case (5) and sealed with a cap assembly (6) to complete the lithium secondary battery (1). The case (5) is cylindrical but is not necessarily limited to this shape and may be, for example, prismatic, thin film, etc.

[0196] Referring to FIG. 6, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound, folded, or stacked to form a battery structure (7). The formed battery structure (7) is housed in a case (5). An electrolyte is injected into the case (5), cross-linked, and sealed to complete the lithium secondary battery (1). The case (5) is prismatic, but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc. A positive lead tab (3') and a positive terminal (3") are electrically connected to the positive electrode (3). A negative lead tab (2') and a negative terminal (2") are electrically connected to the negative electrode (2).

[0197] Referring to FIG. 7, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is housed in a case (5). It may include an electrode tab (70) that serves as an electrical path for inducing the current formed in the battery structure (7) to the outside. An electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is prismatic but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc.

[0198] Referring to FIG. 8, a lithium secondary battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2) and a separator (4) as described above. An electrolyte as described above, including a separator (4), is disposed between the positive electrode (3) and the negative electrode (2) to form a battery structure. For example, the battery structure (7) is stacked in a bicell structure and then housed in a case (5). It may include a positive electrode tab (71) and a negative electrode tab (72) that serve as electrical pathways for inducing current formed in the battery structure (7) to the outside. The electrolyte is injected into the case (5) and sealed to complete the lithium secondary battery (1). The case (5) is prismatic but is not necessarily limited to this shape and may be, for example, cylindrical, thin film, etc.

[0199] However, the present invention is not limited to this, and the case (5) may be configured in various shapes such as circular or pouch type. For example, the pouch-type lithium secondary battery corresponds to the lithium secondary battery (1) of FIGS. 10 to 13 in which a pouch is used as the case (5). The pouch-type lithium secondary battery includes one or more battery structures (7). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2) to form the battery structure (7). The battery structure (7) is stacked in a bicell structure, then impregnated with an electrolyte, and then housed and sealed in a pouch to complete the pouch-type lithium secondary battery.

[0200] Specifically, the battery structure (7) including the aforementioned positive electrode (3), negative electrode (2), and separator (4) is simply stacked and contained in a pouch, or wound into a jelly roll shape or folded and contained in a pouch. Subsequently, an electrolyte is injected into the pouch and sealed to complete the lithium secondary battery (1).

[0201] The case (5) may be made of metal such as aluminum, aluminum alloy, nickel-plated steel, or a laminate film or plastic that constitutes the pouch.

[0202] Lithium secondary battery (1) has excellent lifespan characteristics and high rate characteristics, so it is used in, for example, electric vehicles (EV). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEV). In addition, it is used in fields where a large amount of power storage is required. For example, it is used in electric bicycles, power tools, etc.

[0203] A plurality of lithium secondary batteries (1) are stacked to form a battery module, and a plurality of battery modules form a battery pack. Such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. A battery module includes, for example, a plurality of batteries and a frame that holds them.

[0204] A battery pack includes, for example, a plurality of battery modules and a bus bar connecting them. The battery modules and / or battery pack may further include a cooling device. A plurality of battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0205] The following examples and comparative examples will be explained in more detail. However, the examples are for illustrative purposes only and are not limited thereto.

[0206] Example 1

[0207] A cathode was manufactured by mixing a mixture of a cathode active material and a sacrificial cathode active material, a conductive material, and a binder in a weight ratio of 90:5:5, coating the mixture onto an aluminum metal substrate, drying, and then performing a rolling step. An active material mixed with LiCoO2 powder (LCO, cathode active material) and Li5FeO4 powder (LFO, sacrificial cathode active material) and a carbon conductive material (CNT) were uniformly mixed in a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare an active material slurry such that the weight ratio of active material:carbon conductive material:binder = 90:5:5.

[0208] A cathode containing a lithium host layer was prepared by mixing hard carbon, a conductive material, and a binder in a weight ratio of 90:5:5, coating the mixture onto a copper (Cu) substrate, drying, and then performing a rolling step. CNT was used as the conductive material, and a PVDF solution was used as the binder.

[0209] An electrode assembly was prepared by sequentially stacking a cathode, a separator, and an anode, and a coin cell was prepared by housing it in a coin-type battery case and then injecting a liquid electrolyte to impregnate it.

[0210] At this time, the theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was about 30% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was about 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to about 0.77 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0211] Example 2

[0212] The coin cell manufacturing method is the same as in Example 1.

[0213] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was about 50% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was about 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to about 1.30 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0214] Example 3

[0215] The coin cell manufacturing method is the same as in Example 1.

[0216] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was approximately 70% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was approximately 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to approximately 1.30 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0217] Example 4

[0218] The coin cell manufacturing method is the same as in Example 1.

[0219] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was about 10% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was about 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to about 1.30 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0220] Example 5

[0221] The coin cell manufacturing method is the same as in Example 1.

[0222] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was about 30% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was about 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to about 0.67 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0223] Example 6

[0224] The coin cell manufacturing method is the same as in Example 1.

[0225] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was approximately 70% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was approximately 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to approximately 0.83 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0226] Example 7

[0227] The coin cell manufacturing method is the same as in Example 1.

[0228] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was approximately 30% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was approximately 30%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to approximately 0.77 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0229] Example 8

[0230] The coin cell manufacturing method is the same as in Example 1.

[0231] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was approximately 70% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was approximately 80%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to approximately 1.30 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0232] Example 9

[0233] The coin cell manufacturing method is the same as in Example 1.

[0234] The theoretical charge capacity of LFO and LCO was calculated so that the charge capacity (mAh / g) of LFO was about 30% of the total discharge capacity (mAh / g) of LFO and LCO, the average porosity (%) of the porous structure in the lithium host layer was about 60%, and the ratio of the negative capacity (N) to the positive capacity (P) was adjusted to about 0.5 by considering the loading amount of the positive composite layer and the loading amount of the lithium host layer.

[0235] Comparative Example 1

[0236] The coin cell manufacturing method is the same as in Example 1.

[0237] When manufacturing the anode composite layer, LFO powder is not used, and the average porosity (%) of the porous structure in the lithium host layer is set to 60%, and considering the loading amount of the anode composite layer and the loading amount of the lithium host layer, the ratio of the cathode capacity (N) to the anode capacity (P) is adjusted to be approximately 0.77.

[0238] Comparative Example 2

[0239] The coin cell manufacturing method is the same as in Example 1.

[0240] When manufacturing the anode composite layer, LCO powder is not used, and the average porosity (%) of the porous structure in the lithium host layer is set to 60%, and considering the loading amount of the anode composite layer and the loading amount of the lithium host layer, the ratio of the cathode capacity (N) to the anode capacity (P) is adjusted to be approximately 1.30.

[0241] Evaluation Example 1: Evaluation of Initial Coulomb Efficiency

[0242] After leaving the coin cell manufactured according to the above-described examples and comparative examples at a constant temperature of 25°C for 24 hours, the cell formation process was completed by using a lithium secondary battery charger / discharger (Toyo-System Co., LTD, TOSCAT3600) to charge the cell at a constant current of 0.1C to 4.3V and at a constant voltage of 0.05C as the termination current, and then discharging it at a constant current of 0.1C to 2.8V. During the formation process, the initial efficiency was calculated according to Equation 3 below and is shown in Table 1 below.

[0243] [Equation 3]

[0244] Initial Coulomb efficiency (%) = (1 st Discharge capacity per cycle / 1 st Charge capacity per cycle) × 100

[0245] Initial Coulomb efficiency can reflect the amount of lithium irreversibly lost during the first charging process of the battery. It can also be used as an indicator to evaluate the initial stability of the battery.

[0246] Evaluation Example 2: Evaluation of Dose Retention Rate (%)

[0247] For the lithium secondary battery prepared according to the above-described examples and comparative examples, constant current charging was performed at 45°C at a current rate of 0.1C until the voltage reached 4.30V (vs. Li), and then cut-off was performed at a current rate of 0.05C while maintaining 4.30V in constant voltage mode. Subsequently, during discharge, the battery was discharged at a constant current rate of 0.1C until the voltage reached 3.6V (vs. Li) (formation stage, 1st cycle).

[0248] The formation process was completed by performing this charge-discharge process once.

[0249] A lithium secondary battery that has undergone the formation stage was charged at 45°C with a constant current of 0.33C in a voltage range of 3.6 to 4.3 V relative to lithium metal, and then cut off at a current rate of 0.05C while maintaining 4.30V in constant voltage mode. Subsequently, constant current discharge was performed at 1.0C until a cut-off voltage of 3.6V was reached. The aforementioned charge-discharge process was repeated a total of 100 times. In all charge-discharge cycles, a 5-minute pause was observed after each charge / discharge cycle. Here, the capacity retention rate in the Nth cycle is defined by Equation 4 below.

[0250] [Equation 4]

[0251] Capacity retention rate (%) = (N th Discharge capacity per cycle / 1 st Discharge capacity per cycle) × 100

[0252] The capacity retention rate at the 100th cycle for the coin cells manufactured according to the above-described examples and comparative examples was calculated and listed in Table 1 below. A higher capacity retention rate indicates that the long-term life characteristics of the secondary battery are superior.

[0253] Ratio of charge capacity within the cathode of sacrificial cathode active material (%) Average porosity of lithium host layer (%) N / P ratio Initial Coulomb efficiency (%) Capacity retention rate (%) Example 1 30 % 60 % 0.779 1.1% 95.7 % Example 2 50 % 60 % 1.309 2.8 % 72.1 % Example 3 70 % 60 % 1.309 3.3 % 63.3 % Example 4 10 % 60 % 1.308 8.7 % 90.5 % Example 5 30 % 60 % 0.679 2.5 % 87.0 % Example 6 70 % 60 % 0.838 9.9 % 91.4 % Example 7 30 % 30 % 0.778 6.3 % 93.2 % Example 8 70 % 80 % 1.308 4.6 % 85.0 % Example 930 % 60 % 0.50 92.5 % 73.5 % Comparative Example 10 % 60 % 0.77 81.9 % 68.9 % Comparative Example 2100 % 60 % 1.300 % 0 %

[0254] As shown in Table 1, it was confirmed that the coin cells according to Examples 1 to 9 generally exhibited superior initial Coulomb efficiency and capacity retention rates compared to the coin cells according to Comparative Examples 1 and 2. Through this, it was found that the performance or lifespan characteristics of a lithium secondary battery in which the capacity of the sacrificial cathode active material of the present disclosure is 10% to 70% of the total capacity of the cathode active material and the sacrificial cathode active material are excellent. The capacity retention rate and initial Coulomb efficiency of Examples 1 to 9 appear to be the result of the combined action of the charge capacity ratio within the cathode of the sacrificial cathode active material, the average porosity of the lithium host layer, and the ratio of the negative electrode capacity (N) to the cathode capacity (P). For example, depending on the charge capacity ratio within the cathode of the sacrificial cathode active material, the amount of sacrificial cathode residue within the cathode and the resistance of the cathode plate may change, or the degree to which irreversible lithium loss is compensated by the sacrificial cathode active material may change. Alternatively, depending on the average porosity of the lithium host layer, lithium released from the sacrificial cathode active material may be stored in the lithium host layer only through a mechanism in which it is inserted in an ionic state, or excessive negative side reactions may occur. Alternatively, depending on the ratio of the negative electrode capacity (N) to the positive electrode capacity (P), the amount of lithium ion release from the positive electrode relative to the negative electrode may change.

[0255] In the case of Comparative Example 1, since there was no sacrificial cathode active material, it was confirmed that the initial Coulomb efficiency was lower and the capacity retention rate was generally lower compared to Examples 1 to 9. Through Comparative Example 2, which lacked a cathode active material, it was confirmed that the sacrificial cathode active material used was an irreversible material.

[0256] FIG. 9 is an SEM image showing a cross-section of a positive electrode of a lithium secondary battery according to one embodiment of the present disclosure. FIG. 10 is an SEM image showing a cross-section of a negative electrode of a lithium secondary battery according to one embodiment of the present disclosure. FIG. 9 shows the cross-sectional shape of a positive electrode of a lithium secondary battery according to Example 1, and FIG. 10 shows the cross-sectional shape of a negative electrode of a lithium secondary battery according to Example 2.

[0257] Through the SEM image results of Figure 9, it was confirmed that LFO (sacrificial cathode active material) particles were arranged relatively uniformly between LCO (cathode active material) particles within the cathode.

[0258] Through the SEM image results of Figure 10, it was confirmed that most of the lithium metal was electrodeposited within the pores of the lithium host layer in the cathode, and a small amount of lithium metal was electrodeposited on the upper surface of the lithium host layer.

[0259] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

1. A positive electrode comprising a positive current collector and a positive composite layer disposed on the positive current collector, the composite layer comprising a positive active material and a sacrificial positive active material; A cathode comprising a cathode current collector and a lithium host layer disposed on the cathode current collector and comprising a porous structure; and Electrolyte disposed between the anode and the cathode Includes, Regarding the above lithium host layer, lithium is intercalated in an ionic state, and lithium is plated in a metallic state. A lithium secondary battery in which the capacity of the sacrificial cathode active material is 10% to 70% of the total capacity of the cathode active material and the sacrificial cathode active material.

2. In Paragraph 1, The above sacrificial positive electrode active material comprises any one of Li5FeO4, Li2MoO3, Li6CoO4, Li2O, Li3N, Li3P, or any combination thereof, in a lithium secondary battery.

3. In Paragraph 1, A lithium secondary battery comprising any one of graphite, hard carbon, carbon nanotube (CNT), graphene, silicon-carbon composite, carbon nanofiber (CNF), or any combination thereof, wherein the lithium host layer comprises 4. In Paragraph 1, A lithium secondary battery in which the capacity of the sacrificial cathode active material is 10% to 50% of the total capacity of the cathode active material and the sacrificial cathode active material.

5. In Paragraph 1, A lithium secondary battery, wherein the porous structure comprises pores in which the lithium can be electrodeposited in a metallic state, and the average porosity is 30% to 80%.

6. In Paragraph 5, A lithium secondary battery having an average porosity of 50% to 70%.

7. In Paragraph 1, The negative electrode capacity (N) is defined as the total discharge capacity due to lithium intercalated in an ionic state within the lithium host layer and lithium plated in a metallic state on the upper surface of the lithium host layer and in the pores of the porous structure, and The positive capacity (P) is defined as the total capacity of the sacrificial positive active material and the positive active material, and A lithium secondary battery in which the ratio of the cathode capacity (N) to the anode capacity (P) is 0.5 to 1.

5.

8. In Paragraph 7, A lithium secondary battery in which the ratio of the cathode capacity (N) to the anode capacity (P) is 0.6 to 1.

0.

9. In Paragraph 1, The above porous structure includes pores in which the lithium can be electrodeposited in a metallic state, and the average porosity is 30% to 80%, and The negative electrode capacity (N) is defined as the total discharge capacity due to lithium inserted in an ionic state within the lithium host layer and lithium plated in a metallic state on the upper part of the lithium host layer and in the pores of the porous structure, and The positive capacity (P) is defined as the total capacity of the sacrificial positive active material and the positive active material, and A lithium secondary battery in which the ratio of the cathode capacity (N) to the anode capacity (P) is 0.5 to 1.

5.

10. In Paragraph 9, A lithium secondary battery in which the ratio of the cathode capacity (N) to the anode capacity (P) is 0.6 to 1.

0.

11. In Paragraph 9, A lithium secondary battery having an average porosity of 50% to 70%.

12. In Paragraph 1, A lithium secondary battery in which a lithium metal layer derived from the above positive composite layer is formed on the pores of the above porous structure and on the upper surface of the above lithium host layer.

13. In Paragraph 1, A lithium secondary battery comprising lithium derived from the sacrificial positive electrode active material in the SEI layer formed on the surface of the porous structure.

14. In Paragraph 1, A lithium secondary battery, wherein the above positive composite layer further comprises a conductive material and a binder.

15. In Paragraph 1, A lithium secondary battery, wherein the lithium host layer further comprises a conductive material and a binder.

16. In Paragraph 1, A lithium secondary battery in which the content of the sacrificial positive electrode active material is 10% to 15% by weight with respect to 100% by weight of the positive electrode composite layer.

17. In Paragraph 1, A lithium secondary battery in which the above electrolyte is any one of a liquid electrolyte, a solid electrolyte, or a gel electrolyte.

18. A step of preparing an anode by placing an anode composite layer containing an anode active material and a sacrificial anode active material on an anode current collector; A step of preparing a cathode by placing a lithium host layer including a porous structure on a cathode current collector; and Step of placing an electrolyte between the anode and the cathode Includes, The capacity of the sacrificial cathode active material is 10% to 70% of the total capacity of the cathode active material and the sacrificial cathode active material, and The above porous structure includes pores in which the lithium can be electrodeposited in a metallic state, and the average porosity is 30% to 80%, and The negative electrode capacity (N) is defined as the total discharge capacity due to lithium inserted in an ionic state within the lithium host layer and lithium plated in a metallic state on the upper part of the lithium host layer and in the pores of the porous structure, and The positive capacity (P) is defined as the total capacity of the sacrificial positive active material and the positive active material, and A method for manufacturing a lithium secondary battery, wherein the ratio of the cathode capacity (N) to the anode capacity (P) is 0.5 to 1.5 or less.

19. In Paragraph 18, The capacity of the sacrificial cathode active material is 10% to 50% of the total capacity of the cathode active material and the sacrificial cathode active material, and A method for manufacturing a lithium secondary battery, wherein the average porosity is 50% to 70%.

20. In Paragraph 18, A method for manufacturing a lithium secondary battery, wherein the ratio of the cathode capacity (N) to the anode capacity (P) is 0.6 to 1.0.

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