Positive electrode for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present disclosure relates to a positive electrode for a lithium secondary battery and a secondary battery comprising same. The positive electrode for a lithium secondary battery according to the present disclosure comprises a first positive electrode active material including an overlithiated metal oxide and a second positive electrode active material, wherein the surface of the first positive electrode active material is coated with ceramic particles, and a carbon coating layer may be formed on the surface of the ceramic particles.

Description

Anode for a lithium secondary battery and a lithium secondary battery including the same

[0001] The present disclosure relates to a positive electrode for a lithium secondary battery and a secondary battery including the same.

[0002]

[0003] Recently, accompanied by the rapid proliferation of battery-powered electronic devices such as mobile phones, laptop computers, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries is rapidly increasing. Accordingly, research and development to improve the performance of lithium-ion batteries is actively underway.

[0004] 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.

[0005] Currently commercially available lithium secondary batteries mainly use carbon-based negative electrode active materials such as graphite. Carbon-based negative electrode active materials do not change in volume during charging and discharging, so the stability of lithium secondary batteries is high. The theoretical electric capacity of graphite is small, about 372 mAh / g.

[0006] Lithium metal can be used as a negative electrode active material. The theoretical electric capacity of lithium metal is very high, approximately 3860 mAh / g. During charging and discharging, dendrites can form on the surface of lithium metal due to side reactions with the electrolyte, and as these dendrites grow, they can cause a short circuit between the positive and negative electrodes. Furthermore, during the initial charging and discharging process of a lithium metal secondary battery, lithium ions move to the negative electrode and cause side reactions, forming an SEI layer. Due to the lithium consumption during the formation of this SEI layer, there is a problem of increased irreversible capacity loss. Consequently, the lifespan characteristics and thermal stability of lithium metal batteries containing lithium metal are degraded.

[0007] A method is required to improve the lifespan characteristics and thermal stability of lithium metal secondary batteries containing lithium metal.

[0008] 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.

[0009]

[0010] One embodiment provides a positive electrode for a lithium secondary battery to solve the above technical problem.

[0011] Another embodiment provides a lithium secondary battery comprising a positive electrode for a lithium secondary battery to solve the above technical problem.

[0012]

[0013] A positive electrode for a lithium secondary battery according to one embodiment of the present invention for solving the above technical problem comprises a first positive electrode active material and a second positive electrode active material comprising an overlithiated metal oxide, wherein the surface of the first positive electrode active material is coated with ceramic particles and a carbon coating layer may be formed on the surface of the ceramic particles.

[0014] A lithium secondary battery according to one embodiment of the present invention for solving the above technical problem comprises a positive electrode, a negative electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte, wherein the positive electrode comprises a first positive active material and a second positive active material comprising an overlithiated metal oxide, the surface of the first positive active material is coated with ceramic particles, and a carbon coating layer may be formed on the surface of the ceramic particles.

[0015]

[0016] According to some embodiments of the present disclosure, the irreversible capacity of the anode is increased due to the overlithiated metal oxide contained in the anode, and at the same time, extra lithium can be supplied to the cathode.

[0017] According to some embodiments of the present disclosure, a carbon coating layer with high electrical conductivity is formed on ceramic particles coating a first positive electrode active material comprising a superlithicized metal oxide, thereby increasing the electrical conductivity of the superlithicized metal oxide. Through this, the phenomenon of increased resistance of the positive electrode due to the addition of the superlithicized metal oxide can be suppressed.

[0018] According to some embodiments of the present disclosure, an excess amount of lithium from an overlithiated metal oxide is supplementarily supplied to the negative electrode during the charging and discharging process of the secondary battery, thereby enabling the production of a lithium secondary battery with improved capacity retention rate, lifespan characteristics, and thermal stability.

[0019] 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.

[0020]

[0021] 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.

[0022] FIG. 1 is a schematic diagram showing a positive electrode for a lithium secondary battery according to one embodiment.

[0023] FIG. 2 is a diagram showing a stacked structure of a lithium secondary battery according to one embodiment.

[0024] Figure 3 is a diagram showing the stacked structure of the lithium secondary battery of Figure 1 after charging.

[0025] FIG. 4 is a diagram showing the stacked structure of a lithium secondary battery according to one embodiment.

[0026] FIG. 5 is a perspective view illustrating a lithium secondary battery according to one embodiment.

[0027] FIG. 6 is a perspective view illustrating a lithium secondary battery according to one embodiment.

[0028] FIG. 7 is a perspective view illustrating a lithium secondary battery according to one embodiment.

[0029] FIG. 8 is a perspective view illustrating a lithium secondary battery according to one embodiment.

[0030]

[0031] 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.

[0032] 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.

[0033] 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."

[0034] 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.

[0035] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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”.

[0040] 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.

[0041] 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.

[0042] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0043] In this specification, "alloy" means a mixture of two or more metals.

[0044] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0045] In this specification, "anode active material" refers to an anode material capable of undergoing lithiation and delithiation.

[0046] 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.

[0047] 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.

[0048] In this specification, "charge" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0049] In this specification, "discharge" and "discharge" refer to the process of removing electrochemical energy from a battery.

[0050] In this specification, "anode" and "cathode" refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0051] In this specification, "cathode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0052] Exemplary embodiments will be described in more detail below with reference to the attached drawings.

[0053]

[0054] anode

[0055] A positive active material layer is disposed on a positive current collector to form a positive electrode. A positive active material layer is disposed on an electrolyte, and a positive current collector may be disposed on the positive active material layer.

[0056]

[0057] Anode: Anode active material layer

[0058] FIG. 1 is a schematic diagram showing a positive electrode for a lithium secondary battery according to one embodiment. Specifically, FIG. 1 is a schematic diagram showing the internal composition of a positive electrode active material layer (120) included in the positive electrode.

[0059] Referring to FIG. 1, a positive electrode for a lithium secondary battery according to one embodiment of the present invention may include a first positive electrode active material (122) and a second positive electrode active material (124).

[0060] The first positive active material (122) may include an overlithiated metal oxide. That is, the metal oxide included in the first positive active material (122) may be designed so that the lithium content within the metal oxide structure is higher than the theoretically required amount.

[0061] In one embodiment, the overlithiated metal oxide may include a solid solution of Li2MnO3 and LiMO2 (where M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof).

[0062] For example, a superlithic metal oxide can be represented by the following chemical formula 1.

[0063]

[0064] <Chemical Formula 1>

[0065] Li[Ni x Li 1 / 3-2x / 3 Mn 2 / 3-x / 3 ]O2(0 < X ​​< 0.5)

[0066]

[0067] In one embodiment, the overlithiated metal oxide may have a layered structure. In the first positive electrode active material (122), the metal oxide may have a crystallographic structure in which cations (Li) and metal ions form alternating layers. This may provide a path for lithium ions to move between layers. In one embodiment, the layered metal oxide may be doped with Al to maximize stability.

[0068] According to some embodiments of the present disclosure, the irreversible capacity of the anode can be increased due to the over-lithiated metal oxide included in the anode, while simultaneously supplying extra lithium to the cathode. For example, an over-lithiated metal oxide comprising a solid solution of Li2MnO3 and LiMO2 (where M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof) can supply extra lithium ions from the anode to the cathode through the activation of Li2MnO3 when charging occurs at 4.6V to 4.8V, and the lithium ions thus supplied can compensate for the irreversible capacity of the cathode and improve the lifespan of the secondary battery.

[0069] The metal oxide included in the first positive electrode active material (122) has a high proportion of metal with low electrical conductivity (e.g., Mn), so the charge / discharge efficiency may be lower compared to the second positive electrode active material (124).

[0070] In one embodiment, the surface of the first positive active material (122) may be coated with ceramic particles (126). For example, after coating the first positive active material (122) with ceramic particles (126) by dry milling, the first positive active material (122) and the second positive active material (124) may be mixed to produce a positive active material layer (120).

[0071] The ceramic particles (126) may include any one of Al2O3, ZrO2, TiO2, SiO2, WO3, NiO, Li2O, Co3O4, Bi2O3, MnO2, Na2O, P2O5, B2O3, or a combination thereof.

[0072] Additionally, the average particle size (D50) of the ceramic particles (126) may be 0.1 μm to 3.0 μm, 0.1 μm to 2.5 μm, or 0.3 μm to 0.5 μm so that the ceramic particles (126) are uniformly coated on the surface of the first positive active material (122) to exhibit appropriate characteristics within the positive active material layer (120). Alternatively, the average particle size (D50) of the ceramic particles (126) may be 0.1 μm to 0.5 μm, 0.2 μm to 0.5 μm, or 0.3 μm to 0.5 μm.

[0073] A carbon coating layer (128) may be formed on the surface of the ceramic particles (126). The carbon coating layer (128) can improve the electrical conductivity of the ceramic particles (126) and the first positive active material (122) coated with the ceramic particles (126). The carbon coating layer (128) may be formed by physically adsorbing carbon fibers uniformly or chemically bonding them on the surface of the ceramic particles (126). The carbon coating layer (128) may include pitch-based carbon fibers with high electrical conductivity. For example, the carbon coating layer (128) may include isotropic pitch carbon fibers, mesophase pitch carbon fibers, thermal conductive pitch carbon fibers, electrically conductive pitch carbon fibers, or a combination thereof.

[0074] The carbon coating layer (128) may include amorphous carbon. For example, the amorphous carbon may include hard carbon, soft carbon, carbon black, acetylene black, furnace black, ketjen black, graphene oxide, pitch carbon, or any combination thereof.

[0075] For example, the ratio of the carbon coating layer (128) to the weight of the ceramic particles (126) may be 20 wt% to 70 wt%, 30 wt% to 70 wt%, 40 wt% to 70 wt%, 50 wt% to 70 wt%, or 55 wt% to 67 wt%.

[0076] According to some embodiments of the present disclosure, a ceramic particle (126) coating a first positive electrode active material (122) containing a superlithicized metal oxide has a highly electrically conductive carbon coating layer (128) formed thereon, so that the electrical conductivity of the superlithicized metal oxide can be increased. Through this, the phenomenon of increased resistance of the positive electrode due to the addition of the superlithicized metal oxide can be suppressed.

[0077] The second positive electrode active material (124) may include lithium of stoichiometric composition. The second positive electrode active material (124) may include a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound). 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 may 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.

[0078] 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 O 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 O 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 O 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 L 1 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 Mn2GbO4(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 aFePO4(0.90≤a≤1.8).

[0079] 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.

[0080] For example, the second positive active material (124) can be represented by the following chemical formula 2.

[0081]

[0082] <Chemical Formula 2>

[0083] LiMO2(M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof)

[0084]

[0085] For example, the second positive active material (124) may include lithium iron phosphate.

[0086] For example, the second positive active material (124) may include a metal oxide represented by the following chemical formula 3.

[0087]

[0088] <Chemical Formula 3>

[0089] LiM2O4 (M is Ti, V, Mn, or a combination thereof)

[0090]

[0091] For example, the second positive electrode active material (124) may be a high-nickel positive electrode 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 positive electrode active material can achieve a high capacity and can be applied to a high-capacity, high-density lithium secondary battery.

[0092] For example, the lithium transition metal oxide may be a compound represented by the following chemical formula 4:

[0093]

[0094] <Chemical Formula 4>

[0095] Li a Ni x Co y M z O 2-b A b

[0096]

[0097] In Chemical Formula 4, 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.

[0098] In Chemical Formula 4, 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.

[0099] For example, the lithium transition metal oxide may be at least one of the compounds represented by the following chemical formulas 4-1 and 4-2:

[0100]

[0101] <Chemical Formula 4-1>

[0102] LiNi x Co y Mn z O2

[0103]

[0104] In Chemical Formula 4-1, 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.

[0105]

[0106] <Chemical Formula 4-2>

[0107] LiNi x Co y Al z O2

[0108]

[0109] In Chemical Formula 4-2, 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.

[0110] For example, lithium transition metal oxides are LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04O2 , 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 0.02O2 , LiNi 0.8 Co 0.15 Al 0.05O2 , LiNi 0.8 Co 0.1 Mn 0.2O2 or LiNi 0.88 Co 0.1 Al 0.02O2 It could be.

[0111] For example, the second positive active material (124) may have a coating layer on the surface of a lithium transition metal oxide, or may be used by mixing a lithium transition metal oxide with a coating layer.

[0112] For example, the coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element.

[0113] 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.).

[0114] In addition, the anode may further include a conductive material and a binder.

[0115] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer, and 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 positive active material layer.

[0116] 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.

[0117] 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.

[0118] In one embodiment according to the present invention, the positive active material layer (120) may be formed by mixing a first positive active material (122) and a second positive active material (124) in various molar ratios. For example, the molar ratio of the first positive active material (122) and the second positive active material (124) may be 0.06 : 1 to 15 : 1, 0.1 : 1 to 10 : 1, or 4 : 6 to 7 : 3.

[0119] In one embodiment, the ratio of ceramic particles (126) to the total weight of the first positive active material (122) and the second positive active material (124) may be 0.1 wt% to 10.0 wt%, 0.1 wt% to 9.0 wt%, 0.1 wt% to 8.0 wt%, 0.1 wt% to 7.0 wt%, 0.1 wt% to 6.0 wt%, 0.1 wt% to 5.0 wt%, 0.5 wt% to 3.0 wt%, or 0.5 wt% to 2.0 wt%.

[0120]

[0121] Positive: Positive current collector

[0122] The positive electrode includes a positive electrode current collector. For example, a positive electrode can be prepared by forming a layer of positive electrode active material on the positive electrode current collector.

[0123] For example, the positive current collector 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.

[0124] According to one embodiment, the anode current collector may include aluminum (Al).

[0125] For example, the positive current collector 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 described above.

[0126]

[0127] lithium secondary battery

[0128] A lithium secondary battery according to one embodiment of the present invention may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte for the lithium secondary battery of the present invention as described above.

[0129] For example, a positive electrode for a lithium secondary battery comprises a first positive electrode active material comprising an overlithiated metal oxide and a second positive electrode active material comprising lithium of a stoichiometric composition, the surface of the first positive electrode active material is coated with ceramic particles, and a carbon coating layer may be formed on the surface of the ceramic particles.

[0130] The positive electrode, the negative electrode, and the separator may be impregnated with or in contact with an electrolyte. In a lithium secondary battery according to one embodiment, the negative electrode may be free of a negative electrode active material layer before charging is performed. Additionally, the electrical capacity of the negative electrode may be less than 100% of the electrical capacity of the positive electrode.

[0131] FIG. 2 is a diagram showing a stacked structure of a lithium secondary battery according to one embodiment. FIG. 3 is a diagram showing the stacked structure of the lithium secondary battery of FIG. 2 after charging. FIG. 4 is a diagram showing a stacked structure of a lithium secondary battery according to one embodiment.

[0132] FIG. 2 is a drawing showing a stacked structure of a non-anode lithium secondary battery (100), and FIG. 3 may correspond to a drawing showing lithium metal precipitated on a negative current collector as the non-anode lithium secondary battery (100) is charged. FIG. 4 may correspond to a drawing showing a lithium metal secondary battery (300) in which lithium metal is used as a negative active material layer. The thickness of each layer shown in FIG. 2 to FIG. 4 is shown as an arbitrary size and is not necessarily limited thereto.

[0133] A lithium secondary battery according to one embodiment comprises a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. The electrolyte may have a solid, liquid, or gel form. Although the present disclosure describes lithium metal secondary batteries primarily, it is not limited thereto and may be, for example, a lithium primary battery, and may also be applied to lithium-sulfur batteries, lithium-air batteries, etc.

[0134] Referring to FIG. 2, a lithium secondary battery (100) according to one embodiment may include a positive electrode (130), a negative electrode, and an electrolyte (160) disposed between the positive electrode (130) and the negative electrode.

[0135] A lithium secondary battery (100) according to one embodiment may include a negative electrode current collector (140), an electrolyte (160) disposed on top of the negative electrode current collector (140), and a positive electrode (130) disposed on top of the electrolyte (160), as shown in FIG. 2. The negative electrode may include a negative electrode current collector (140) in which the negative electrode active material layer is free, and the positive electrode (130) may include a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on the positive electrode current collector (110). Here, the positive electrode active material layer (120) may be the positive electrode active material layer (120) described above with reference to FIG. 1.

[0136] A lithium secondary battery (300) according to one embodiment may further include a lithium metal layer (350) disposed between a negative electrode current collector (340) and an electrolyte (360), as shown in FIG. 4. In this case, the negative electrode may include a lithium metal layer (350) disposed between the negative electrode current collector (340) and the electrolyte (360). For example, the lithium secondary battery (300) may include a negative electrode current collector (340), a lithium metal layer (350) disposed on top of the negative electrode current collector (340), an electrolyte (360) disposed on top of the lithium metal layer (350), and a positive electrode (330) disposed on top of the electrolyte (360). The positive electrode (330) may include a positive electrode current collector (310) and a positive electrode active material layer (320) disposed on the positive electrode current collector (310). Accordingly, the electrolyte (360) can be placed between the positive active material layer (320) and the lithium metal layer (350).

[0137] For example, the lithium metal layer (350) may include lithium metal or a lithium alloy. For example, the lithium metal layer (350) may be reduced in thickness by dissociating into lithium ions and metal cations during the discharge process. Conversely, the lithium metal layer (350) may be increased in thickness by electrodepositing lithium ions during the charging process.

[0138] According to one embodiment, a lithium secondary battery (100, 300) comprising an electrolyte (160, 360) may further include a protective layer (not shown) disposed between a negative electrode and the electrolyte. For example, the protective layer may be formed between a negative electrode current collector (140) and the electrolyte (160). Alternatively, the protective layer may be formed between a lithium metal layer (350) and the electrolyte (360). According to one embodiment, the protective layer of the lithium secondary battery (100, 300) comprises an inorganic oxide, and the electrolyte (160, 360) may be disposed between the protective layer and the positive electrode (130, 330).

[0139] According to one embodiment, one or more stacked structures of the lithium secondary battery (100, 200, 300) as described above may be stacked or wound and accommodated in a case, and the case may be classified into cylindrical, prismatic, thin film, coin, pin type, etc.

[0140] According to some embodiments of the present disclosure, an excess amount of lithium from an overlithiated metal oxide is supplementarily supplied to the negative electrode during the charging and discharging process of the secondary battery, thereby enabling the production of a lithium secondary battery with improved capacity retention rate, lifespan characteristics, and thermal stability.

[0141] The present disclosure describes primarily lithium metal secondary batteries but is not limited thereto; for example, it may be a lithium primary battery, and may also be applied to lithium-sulfur batteries, lithium-air batteries, etc. The aforementioned positive electrode, negative electrode, and separator may be laminated or wound and accommodated in a case, and the case may be classified into cylindrical, prismatic, thin-film, coin, pin, etc.

[0142] FIGS. 5 to 8 are schematic diagrams illustrating a lithium secondary battery according to one embodiment, where 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.

[0143] 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.

[0144] 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).

[0145] 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.

[0146] 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.

[0147] 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. 5 to 8 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.

[0148] 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).

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153]

[0154] Cathode: Cathode current collector

[0155] The negative current collector may not include a negative active material layer. In a negative current collector that does not include a negative active material layer, lithium metal may be plated onto the negative current collector by charging. The plated metal layer may comprise plated lithium, lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, an organic compound containing lithium, or a combination thereof. The metal layer may comprise 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.

[0156] The material constituting the negative electrode current collector may be any material that does not react with lithium, that is, a material that does not form an alloy or compound with lithium and possesses conductivity. The metal substrate is, for example, a metal or an alloy. The metal substrate may be composed of, for example, 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 alloys thereof. The negative electrode current collector may have a form 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 forms and any form used in the relevant technical field is possible.

[0157] The negative current collector comprises, for example, a first metal substrate. The first metal substrate comprises the first metal as a main component or is composed of the first metal. The first metal substrate comprises the first metal as a main component or is composed 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.

[0158] 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 composed of, for example, one of the metals described above, or may be composed of an alloy of two or more metals. The first metal substrate is, for example, in the form of a sheet or foil.

[0159] The negative current collector may further include a coating layer (not shown) containing a second metal on a first metal substrate.

[0160] The cathode current collector 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. 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 can be suppressed more effectively. The coating layer may have a single-layer structure or a multilayer structure of two or more layers. The coating layer may have a two-layer structure including, for example, a first coating layer and a second coating layer. The coating layer may have 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.

[0161] For example, the cathode current collector may have a reduced thickness compared to a conventional cathode current collector. Accordingly, the cathode according to the present disclosure is distinguished from a conventional electrode comprising a thick film current collector by including, for example, a thin film current collector.

[0162] As a result, the energy density of a lithium metal secondary battery employing such an electrode is increased. The thickness of the negative electrode current collector may be, for example, less than 15 μm, 14.5 μm or less, or 14 μm or less. The thickness of the negative electrode current collector may be, for example, 0.1 μm to 15 μm, 1 μm to 14.5 μm, 2 μm to 14 μm, 3 μm to 14 μm, 5 μm to 14 μm, or 10 μm to 14 μm.

[0163] The cathode current collector may have a form 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 forms, and any form used in the relevant technical field is possible.

[0164] The negative current collector 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.

[0165] For example, the base film may include, for example, 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.

[0166] 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.

[0167] 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 μm to 50 μm, 1.5 μm to 50 μm, 1.5 μm to 40 μm, or 1 μm to 30 μm. By having the base film within this range of thickness, 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° (Celsius), 100° to 250° (Celsius) or lower, or 100° to 200° (Celsius). By having the base film within this range of melting point, the base film can melt during the welding process of the lead tab and be easily bonded to the lead tab. To improve the adhesion between the base film and the metal substrate layer, a surface treatment such as corona treatment may be performed on the base film.The thickness of the metal substrate layer may be, for example, 0.01 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 the metal substrate layer within this thickness 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 the metal piece within this thickness 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.

[0168] According to one embodiment, a negative electrode active material layer may be free on the negative electrode current collector before charging and discharging. For example, a lithium metal layer may be free on the negative electrode current collector before charging and discharging.

[0169] According to one embodiment, a lithium metal layer including a plate-shaped lithium metal thin film may be disposed on a negative electrode current collector before performing charging and discharging.

[0170] According to one embodiment, the cathode may further include an interlayer disposed between the cathode current collector and the lithium metal layer.

[0171] According to one embodiment, the interlayer may be placed directly on, for example, one or both sides of the negative current collector. Therefore, no other layer may be placed between the negative current collector and the interlayer. By placing the interlayer directly on one or both sides of the negative current collector, the bonding strength between the negative current collector and the lithium metal layer may be further improved.

[0172] The thickness of the intermediate layer (not shown) may be, for example, 30% or less of the thickness of the cathode current collector. The thickness of the intermediate layer (not shown) 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 cathode current collector. 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.

[0173] By having the intermediate layer have a thickness within this range, the bonding strength between the cathode current collector and the metal layer is further improved, and the increase in interfacial resistance can be suppressed.

[0174] 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 and the lithium metal layer can be further improved. The binder included in the intermediate layer is, for example, a conductive binder or a non-conductive binder.

[0175] 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.

[0176] 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), polyaniline, and polyacetylene. Ion-conducting binders may include polar functional groups. Ion-conducting binders containing polar functional groups are, for example, Nafion, Aquivion, Flemion, These include Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether 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.

[0177] 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.

[0178] 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.

[0179] The intermediate layer can be disposed on the cathode current collector in a dry manner by deposition, for example, CVD, PVD, etc. The intermediate layer can be disposed on the cathode current collector in a wet manner by, for example, spin coating, dip coating, etc. The intermediate layer can be disposed on the cathode current collector by, for example, depositing a carbon-based conductive material on the cathode current collector by deposition. The dry-coated intermediate layer consists of a carbon-based conductive material and may not contain a binder. Alternatively, the intermediate layer can be disposed on the cathode current collector by, for example, coating a composition comprising a carbon-based conductive material, a binder, and a solvent onto the surface of the cathode current collector and drying it. The intermediate layer may have a single-layer structure or a multilayer structure comprising multiple layers.

[0180]

[0181] Cathode: Lithium metal layer

[0182] Referring to FIG. 4, the lithium secondary battery may further include a metal layer disposed between the negative electrode current collector and the electrolyte. For example, the lithium metal layer may include lithium metal or a lithium alloy. For example, the lithium metal layer may be a negative electrode active material layer. For example, the lithium metal layer may be a lithium electrodeposited layer.

[0183] For example, a lithium metal layer can be formed as lithium ions contained in the electrolyte are electrodeposited onto the negative current collector while the lithium secondary battery is being charged. For example, the lithium metal layer may include a lithium alloy and lithium metal. For instance, the lithium alloy included in the lithium metal layer weakens the reactivity of the lithium metal, thereby effectively preventing adverse reactions between the lithium metal layer and the electrolyte. Additionally, the lithium metal layer has excellent electrical conductivity, which can reduce the internal resistance of the lithium secondary battery containing it. Accordingly, the lithium secondary battery containing the lithium metal layer can improve not only its lifespan characteristics but also its charge / discharge efficiency.

[0184] According to one embodiment, the lithium metal layer may comprise, for example, lithium foil, lithium powder, plated lithium, a carbon-based material, or a combination thereof. For example, the lithium metal layer may comprise lithium foil. In this case, the lithium metal layer may be a negative electrode active material layer. For example, the lithium metal layer may be introduced by coating a slurry containing lithium powder and a binder, etc., onto a negative electrode current collector. For example, the binder may be a fluorine-based binder such as polyvinylidene fluoride (PVDF).

[0185] According to one embodiment, it may comprise only lithium metal or lithium alloy electrodeposited with a lithium metal layer. In this case, the lithium metal layer may be a lithium electrodeposited layer.

[0186] 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.

[0187] For example, the thickness of the lithium metal layer may be, for example, 0.1 μm to 100 μm, 0.1 μm to 80 μm, 1 μm to 80 μm, or 10 μm to 80 μm, but is not necessarily limited to these ranges and can be adjusted according to the required shape, capacity, etc. of the lithium secondary battery. If the thickness of the lithium metal layer increases excessively, the structural stability of the lithium secondary battery may decrease and side reactions may increase. If the thickness of the lithium metal layer is excessively small, the energy density of the lithium metal secondary battery may decrease.

[0188] According to one embodiment, the thickness of the lithium foil included in the lithium metal layer may be, for example, 1 μm to 50 μm, 1 μm to 30 μm, or 10 μm to 30 μm, or 10 μm to 80 μm. By having the lithium foil within this range of thickness, the lifespan characteristics of the lithium metal secondary battery can be further improved.

[0189] According to one embodiment, the particle size of the lithium powder included in the lithium metal layer may be, for example, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 1 μm. By having the lithium powder have a thickness within this range, the lifespan characteristics of the lithium secondary battery can be further improved.

[0190]

[0191] electrolytes

[0192] The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0193] The electrolyte 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.

[0194] For example, the organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0195] Carbonate-based solvents such as fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) may be used.

[0196] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0197] Dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used as ether-based solvents.

[0198] Cyclohexanone and the like can be used as ketone-based solvents. Ethyl alcohol and isopropyl alcohol and the like can be used as alcohol-based solvents, and nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group) and amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes and the like can be used as aprotic solvents.

[0199] 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.

[0200] Any lithium salt used as a lithium salt in the relevant technical field is also acceptable. Examples of lithium salts include LiPF6, LiTFSI (Lithium Bis(trifluoromethanesulfonyl)imide), LiDFOB (Lithium Difluoro(oxalato)borate), 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.

[0201] Solid electrolytes are, for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, polymeric solid electrolytes, or combinations thereof.

[0202] 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 P 3-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).

[0203] 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. In addition, Li3PO4, halogen, halogen compound, 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 0.75 An 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-Lip 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.

[0204] 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.

[0205] A polymeric solid electrolyte is an electrolyte that, for example, contains a mixture of a lithium salt and a polymer, or contains a polymer having ion-conducting functional groups. 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, DPHA (Dipentaerythritol Hexaacrylate), 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), Polyaniline, Polyacetylene, 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), Polystyrene sulfonate,It may be PSS), lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi+), or a combination thereof, but is not limited thereto; any that is used as a polymer electrolyte in the relevant technical field is acceptable. Any lithium salt that can be used as a lithium salt in the relevant technical field is acceptable. Examples of lithium salts include LiPF6, LiTFSI (Lithium Bis(trifluoromethanesulfonyl)imide), LiDFOB (Lithium Difluoro(oxalato)borate), 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.

[0206] A gel electrolyte is, for example, a gel polymer electrolyte. A gel polymer electrolyte is an electrolyte that includes, for example, a liquid electrolyte and a polymer, or includes an organic solvent and a polymer having ion-conducting functional groups. 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 the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the 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 solely 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. The gel electrolyte may further include inorganic particles.

[0207]

[0208] separator

[0209] A lithium battery according to one embodiment may further include a separator (not shown).

[0210] 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.

[0211] 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.

[0212] 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.

[0213] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0214] 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.

[0215] 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.

[0216] This will be explained in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only and are not limited thereto.

[0217]

[0218] Example 1: Preparation of a lithium secondary battery

[0219] Al2O3 with an average particle size (D50) of 0.3 μm was used as the ceramic particles. The ceramic particles composed of Al2O3 were mixed with pitch-based carbon fibers and heat-treated at over 700°C to coat the surface of the ceramic particles with carbonized carbon fibers. At this time, the ratio of the carbon coating layer to the ceramic particles was 55 wt%. Subsequently, the Al2O3 microparticles coated with pitch-based carbon fibers were used as the first cathode active material, Li 1.22 [Ni 0.17 Mn 0.61 A dry coating was applied to the surface of O2, and this was mixed with LiCoO2, which is the second positive active material, to prepare a positive active material layer slurry. The molar ratio of the first positive active material to the second positive active material is 4:6. Subsequently, the slurry was applied onto an aluminum foil, which is the positive current collector, to manufacture a positive electrode. The weight ratio of ceramic particles to the total weight of the first positive active material and the second positive active material is 0.5 wt%.

[0220] In addition, a slurry of hard carbon, binder (carboxymethyl cellulose, CMC), and binder (styrene-butadiene rubber, SBR) mixed in a weight ratio of 97.5:1.5:1.0 was uniformly coated onto a copper foil to a thickness of 40 μm to manufacture a cathode.

[0221] LiPF6 (Lithium Hexafluorophosphate), LiTFSI (Lithium Bis(trifluoromethanesulfonyl)imide), and LiDFOB (Lithium Difluoro(oxalato)borate) were added sequentially as lithium salts to a solvent mixed with EC (Ethylene Carbonate), DEC (Diethyl Carbonate), and FEC (Fluoroethylene Carbonate) in a weight ratio of 30:50:20, and the molar concentrations were adjusted to 0.6 M, 0.3 M, and 0.6 M, respectively. Subsequently, 4 wt% DPHA (Dipentaerythritol Hexaacrylate) was added as a crosslinking agent to the liquid lithium salt-solvent mixture, stirred to ensure the crosslinking agent was uniformly dispersed in the mixture, and then heat-treated to prepare an electrolyte.

[0222]

[0223] Examples 2 to 8

[0224] For each example, the first positive electrode active material, the second positive electrode active material, and the ceramic particles were prepared as indicated in Table 1, and the positive electrode was manufactured in the same manner as in Example 1.

[0225]

[0226] Comparative Example 1

[0227] As indicated in Table 1, the anode was manufactured in the same manner as in Example 1, except that the anode active material layer slurry was prepared using only the second anode active material.

[0228]

[0229] Comparative Example 2

[0230] As indicated in Table 1, the anode was manufactured in the same manner as in Example 1, except that the anode active material layer slurry was prepared using only the first anode active material.

[0231]

[0232] Comparative Example 3

[0233] As indicated in Table 1, the anode was manufactured in the same manner as in Example 1, except that the anode active material layer slurry was prepared using only the first anode active material and ceramic particles without a carbon coating layer.

[0234]

[0235] Comparative Example 4

[0236] As indicated in Table 1, the anode was manufactured in the same manner as in Example 1, except that the anode active material layer slurry was prepared using only the first anode active material and the second anode active material.

[0237]

[0238] Molar ratio between the first and second positive active materials Ceramic particles (Al2O3) weight ratio (wt%) Average particle size of ceramic particles (D50, μm) Ratio of carbon coating layer (wt%) First positive active material Second positive active material Example 1 460.50.355 Example 2 460.80.357 Example 3 731.70.363 Example 4 732.00.367 Example 5 1151.70.363 Example 6 738.00.363 Example 7 460.50.322 Example 8 460.52.555 Comparative Example 1-1---Comparative Example 21----Comparative Example 31-0.50.3-Comparative Example 446---

[0239]

[0240] Evaluation Example 1: DC-IR Measurement

[0241] A battery manufactured according to the examples and comparative examples was charged at 25°C with a constant current / constant voltage under cut-off conditions of 0.2C, 0.01V, and 0.01C, rested for 10 minutes, discharged under a constant current of 0.2C and 1.5V cut-off condition, and rested for 10 minutes. A single charge-discharge cycle was performed, and the voltage drop (V) occurring while flowing a current of 8C for 10 seconds at SOC50 was measured. The resistance value was calculated from the measured voltage and the applied current (8C), and the result was expressed as DC internal resistance (DC-IR). SOC50 is a state where the battery is charged to 50% of its total charge capacity when the total charge capacity is set to 100%, which means that the battery has been discharged to 50% when viewed as a discharge state.

[0242] The results are shown in the table below.

[0243]

[0244] Evaluation Example 2: Charge / Discharge Cycle Measurement Reaching a Capacity Retention Rate of 80%

[0245] A lithium secondary battery composed of each anode, cathode, separator, and electrolyte prepared according to the examples and comparative examples was manufactured, and a charge / discharge evaluation was performed.

[0246]

[0247] Manufacturing of charge / discharge evaluation cells

[0248] A single-plate pouch cell was fabricated to perform the above charge-discharge evaluation. A single-plate pouch cell was fabricated by sequentially stacking a separator and a cathode on top of the respective anodes corresponding to the examples and comparative examples inside an aluminum pouch, and then vacuum sealing the pouch. The cathode and anode were configured to be connected to external wires by connecting them to tabs made of nickel and aluminum, respectively. In addition, the sealed pouch cell, into which a gel electrolyte (GPE) was injected, was left at room temperature for 12 hours to allow the electrolyte to fully impregnate the pores of the anode, and subsequently, was left in an 80°C oven for 3 hours to cure the gel electrolyte (GPE) impregnated in all the pores inside the pouch cell.

[0249]

[0250] Charge / Discharge Evaluation in Progress

[0251] The pouch cell manufactured through the above process was charged with a constant current at a rate of 0.1C at 45°C until the voltage reached 4.30V (vs. Li), and then cut off at a current rate of 0.05C while maintaining 4.30V in constant voltage mode. Subsequently, it was discharged with a constant current rate of 0.1C until the voltage reached 3.6V (vs. Li) during discharge (Formation Stage 1).

[0252] A lithium secondary battery that has undergone the first stage of formation was charged at 45°C with a constant current of 0.2C 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 0.2C until a cut-off voltage of 3.6V was reached (second stage of formation).

[0253] The Mars stage was completed by going through the above Mars 1 and 2 stages one cycle each.

[0254] A lithium secondary battery with a completed 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.

[0255] The aforementioned charge / discharge process was repeated a total of 300 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 the following formula.

[0256]

[0257] Capacity Retention Rate (%) = (Discharge Capacity at Nth Cycle / Discharge Capacity at 1st Cycle) × 100

[0258]

[0259] DC-IR was measured according to Evaluation Example 1 above and recorded in Table 2 below.

[0260] In addition, the cycles reaching a capacity retention rate of 80% according to Evaluation Example 2 above were measured and listed in Table 2 below.

[0261]

[0262] Classification DC-IR(Ω) Cycles Reaching 80% Capacitance Retention Rate Example 11.8272 Example 21.7275 Example 32.2289 Example 42.3286 Example 52.8124 Example 62.3227 Example 74.8155 Example 83.8189 Comparative Example 14.972 Comparative Example 29.299 Comparative Example 39.794 Comparative Example 45.4107

[0263]

[0264] 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.

[0265]

[0266] The positive electrode for a lithium secondary battery according to the present invention and the lithium secondary battery including the same can supply additional lithium to the negative electrode by applying a first positive electrode active material comprising an overlithiated metal oxide, thereby compensating for irreversible capacity loss and improving the capacity retention rate, lifespan characteristics, and thermal stability of the battery. Since a lithium secondary battery having these characteristics can be applied to various electronic devices and power storage systems requiring high energy density and high output, such as electric vehicles (EVs), hybrid electric vehicles (PHEVs), energy storage systems (ESS), laptop computers, smartphones, power tools, and electric bicycles, it has high potential for industrial use.

Claims

1. A first positive electrode active material comprising an overlithiated metal oxide; and Second positive active material; Includes, The surface of the first positive active material is coated with ceramic particles, and A carbon coating layer is formed on the surface of the ceramic particles. Cathode for lithium secondary batteries.

2. In Paragraph 1, The above-mentioned overlithiated metal oxide comprises solid solutions of Li2MnO3 and LiMO2 (where M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof), Cathode for lithium secondary batteries.

3. In Paragraph 2, The above-mentioned overlithiated metal oxide is a positive electrode for a lithium secondary battery represented by the following chemical formula 1. <Chemical Formula 1> Li[Ni x Li 1 / 3-2x / 3 Mn 2 / 3-x / 3 ]O2(0 <x<0.5) 4. In Paragraph 1, The above-mentioned overlithiated metal oxide has a layered structure, Cathode for lithium secondary batteries.

5. In Paragraph 1, The above second positive active material is a positive electrode for a lithium secondary battery represented by the following chemical formula 2. <Chemical Formula 2> LiMO2(M is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof) 6. In Paragraph 1, The above second positive active material is a positive electrode for a lithium secondary battery comprising lithium iron phosphate.

7. In Paragraph 1, The above second positive active material comprises a metal oxide represented by the following chemical formula 3, a positive electrode for a lithium secondary battery. <Chemical Formula 3> LiM2O4 (M is Ti, V, Mn, or a combination thereof) 8. In Paragraph 1, The molar ratio of the first positive active material to the second positive active material is 0.06 : 1 to 15 : 1, Cathode for lithium secondary batteries.

9. In Paragraph 1, The ceramic particles above comprise any one of Al2O3, ZrO2, TiO2, SiO2, WO3, NiO, Li2O, Co3O4, Bi2O3, MnO2, Na2O, P2O5, B2O3, or a combination thereof. Cathode for lithium secondary batteries.

10. In Paragraph 1, The average particle size (D50) of the ceramic particles is 0.1 μm to 3.0 μm, Cathode for lithium secondary batteries.

11. In Paragraph 1, The ratio of the ceramic particles to the total weight of the first positive active material and the second positive active material is 0.1 wt% to 10 wt%, Cathode for lithium secondary batteries.

12. In Paragraph 1, The carbon coating layer above comprises amorphous carbon, Cathode for lithium secondary batteries.

13. In Paragraph 1, The ratio of the carbon coating layer to the weight of the ceramic particles is 20 wt% to 70 wt%, Cathode for lithium secondary batteries.

14. Anode; cathode; A separator interposed between the above cathode and the above anode; and electrolytes Includes, The above anode is, A first positive active material comprising an overlithiated metal oxide; and It includes a second positive electrode active material, The surface of the first positive active material is coated with ceramic particles, and A lithium secondary battery having a carbon coating layer formed on the surface of the ceramic particles.

15. In Paragraph 14, A lithium secondary battery in which, prior to charging, the negative electrode active material layer is absent (free) on the negative electrode, or the electrical capacity of the negative electrode relative to the electrical capacity of the positive electrode is less than 100%.

16. In Paragraph 14, The above-mentioned overlithiated metal oxide comprises a solid solution of Li2MnO3 and LiMO2 (where M is Co, Ni, Mn, or a combination thereof), a lithium secondary battery.

17. In Paragraph 14, The above-mentioned overlithiated metal oxide is a lithium secondary battery represented by the following chemical formula 1. <Chemical Formula 1> Li[Ni x Li 1 / 3-2x / 3 Mn 2 / 3-x / 3 ]O2(0 <x<0.5) 18. In Paragraph 14, The above-mentioned overlithiated metal oxide has a layered structure, Lithium secondary battery.

19. In Paragraph 14, The above second positive active material is a lithium secondary battery represented by the following chemical formula 2. <Chemical Formula 2> LiMO2(M is Co, Ni, Mn or a combination thereof) 20. In Paragraph 14, The molar ratio of the first positive active material to the second positive active material is 0.06 : 1 to 15 : 1, Lithium secondary battery.

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