Lithium transfer film and manufacturing method thereof, electrode for lithium secondary battery to which lithium transfer film is transferred, and lithium secondary battery comprising same

Abstract

The present invention relates to: a lithium transfer film and a manufacturing method thereof; an electrode for a lithium secondary battery to which the lithium transfer film is transferred; and a lithium secondary battery comprising same, the lithium transfer film including: a base layer; a lithium metal layer; and a passivation layer, wherein the base layer has a Young's modulus of 4.2 GPa or greater in both the machine direction (MD) and the transverse direction (TD), an elongation of 130% or less in both the MD and the TD, and a deviation in elongation between the MD and the TD of ±3.5 or less, thereby suppressing or preventing damage to the passivation layer.

Description

Lithium transfer film and method for manufacturing the same, lithium secondary battery electrode onto which lithium transfer film is transferred, and lithium secondary battery including the same

[0001] This invention claims the benefit of Korean Patent Application No. 10-2023-0183303, filed with the Korean Intellectual Property Office on December 15, 2023, and Korean Patent Application No. 10-2024-0182140, filed with the Korean Intellectual Property Office on December 10, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a lithium transfer film and a method for manufacturing the same, an electrode for a lithium secondary battery onto which the lithium transfer film is transferred, and a lithium secondary battery including the same.

[0003] Due to the rapid increase in fossil fuel use, the demand for alternative or clean energy is increasing, and as part of this, the most actively researched field is power generation and storage using electrochemical reactions.

[0004] A representative example of an electrochemical device that currently utilizes this electrochemical energy is the secondary battery, and its application area is gradually expanding.

[0005] Meanwhile, with the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and widely used. As the scope of lithium secondary batteries expands to large-capacity devices such as electric vehicles, research into high-capacity lithium secondary batteries is also actively underway. Furthermore, active research is being conducted on methods for manufacturing high-density electrodes with higher energy density per unit volume as electrodes for these high-capacity lithium secondary batteries. The trend toward higher loading is increasing to enhance energy density.

[0006] [Prior Art Literature]

[0007] [Patent Document]

[0008] (Patent Document 1) Korean Patent Registration No. 10-2475886

[0009] The present invention provides a lithium transfer film capable of suppressing or preventing damage to a passivation layer capable of suppressing lithium loss that may occur during a lithium transfer process, a method for manufacturing the same, an electrode for a lithium secondary battery onto which the lithium transfer film is transferred, and a lithium secondary battery including the same.

[0010] One embodiment of the present specification includes a substrate layer; a lithium metal layer and a passivation layer,

[0011] The above-mentioned substrate layer provides a lithium transfer film having a Young's modulus of 4.2 GPa or more in the machine direction (MD) and transverse direction (TD), an elongation in the MD and TD of 130% or less, and a deviation in the elongation in the MD and TD of ±3.5 or less.

[0012] One embodiment of the present specification comprises the steps of depositing a lithium metal layer on one surface of a substrate layer; and

[0013] A step of forming a passivation layer on the opposite side of the surface on which the substrate layer of the lithium metal layer is located,

[0014] The above-mentioned substrate layer provides a method for manufacturing a lithium transfer film, wherein the Young's Modulus of MD and TD is 4.2 GPa or more, the elongation of MD and TD is 130% or less, and the deviation of the elongation of MD and TD is ±3.5 or less.

[0015] One embodiment of the present specification comprises an electrode current collector layer;

[0016] electrode active material layer; and

[0017] The aforementioned lithium transfer films are sequentially laminated,

[0018] An electrode intermediate is provided in which the passivation layer of the lithium transfer film faces the electrode active material layer.

[0019] One embodiment of the present specification comprises an electrode current collector layer; and

[0020] The aforementioned lithium transfer films are sequentially laminated,

[0021] An electrode intermediate is provided in which the passivation layer of the lithium transfer film faces the electrode current collector layer.

[0022] One embodiment of the present specification includes an electrode active material layer or an electrode current collector layer,

[0023] An electrode for a lithium secondary battery is provided, in which the above-described lithium transfer film is transferred to at least one surface of the electrode active material layer or the electrode current collector layer.

[0024] Another embodiment of the present specification is an electrode for a lithium secondary battery as described above;

[0025] membrane; and

[0026] A lithium secondary battery including an electrolyte is provided.

[0027] Another embodiment of the present disclosure provides a battery module or battery pack including the aforementioned lithium secondary battery.

[0028] Finally, one embodiment of the present disclosure provides a battery pack comprising the battery module described above.

[0029] The present invention can reduce lithium loss and reduce the risk of ignition by suppressing side reactions due to lithium oxide or nitride that may occur on the surface of a lithium transfer film during a lithium transfer process through a passivation layer, and can provide a lithium transfer film and a method for manufacturing the same, an electrode for a lithium secondary battery onto which the lithium transfer film is transferred, and a lithium secondary battery including the same, characterized in that the passivation layer satisfies certain mechanical properties of a substrate layer to suppress or prevent damage due to tension applied by a roll-to-roll processing.

[0030] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0031] Figure 1 is a diagram showing a laminated structure of a lithium transfer film according to one embodiment of the present invention.

[0032] Figure 2 is a flow chart explaining a method for manufacturing a lithium transfer film according to one embodiment of the present invention.

[0033] FIG. 3 is a diagram showing the laminated structure of a lithium-ion negative electrode manufactured according to one embodiment of the present invention.

[0034] FIG. 4 is a diagram showing a laminated structure of a lithium secondary battery manufactured according to one embodiment of the present invention.

[0035] Before explaining the present invention, some terms are first defined.

[0036] When a part of this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0037] In this specification, ‘p to q’ means a range of ‘p or more and q or less.’

[0038] In this specification, "specific surface area" is measured by the BET (Brunauer, Emmett, Teller) method, and is calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using, for example, BELSORP-mini II of BEL Japan. In this specification, the BET specific surface area may mean the specific surface area measured by the above measurement method.

[0039] In this specification, “strain” is the amount of deformation of a material caused by stress occurring within the material divided by the original length.

[0040] In this specification, "Young's Modulus" is a mechanical property that measures the stiffness of a solid material, and is an elastic coefficient that defines the relationship between stress (force per unit area) and strain of a linear elastic material in a uniaxial deformation region, and can be used as the same concept as the elastic modulus. If expressed as a formula, it is as shown in Formula 1 below, and a low Young's Modulus means a high strain, and a high Young's Modulus means a low strain.

[0041] [Formula 1]

[0042]

[0043] In the above formula 1.

[0044] E represents Young's modulus, σ represents stress, and ε represents strain.

[0045] In this specification, “elongation” refers to the maximum elongation when a material breaks due to a tensile load (stress), expressed as a percentage, and can be used as a concept identical to strain, and a high elongation means that the material has high ductility.

[0046] In this specification, the Young's modulus and elongation can be measured by cutting or punching a film to be measured into a sample shape of 25.4 mm x 250 mm, and collecting the sample, and using, for example, the tensile test method of ASTM D882 under room temperature conditions.

[0047] In this specification, “MD (machine direction)” refers to the direction in which the film is run during film manufacturing, and can be used as the same concept as the longitudinal direction or machine direction.

[0048] In this specification, “TD (transverse direction)” refers to a direction perpendicular to the direction of travel of the film during film manufacturing, and can be used as the same concept as the transverse direction.

[0049] In this specification, the "deviation of elongation" refers to the difference between the MD elongation measurement value and the TD elongation measurement value from the average value of the MD elongation measurement value and the TD elongation measurement value. Specifically, it can be calculated using the following [Equation 2].

[0050] [Formula 2]

[0051] Belief deviation = {(MD believer) + (TD believer)} / 2 - (Belief of MD or TD)

[0052] In this specification, "Dn" means particle size distribution, and means the particle size at the n% point of the cumulative distribution of particle numbers according to particle size. That is, D50 is the particle size (average particle size) at the 50% point of the cumulative distribution of particle numbers according to particle size, D90 is the particle size at the 90% point of the cumulative distribution of particle numbers according to particle size, and D10 is the particle size at the 10% point of the cumulative distribution of particle numbers according to particle size. Meanwhile, the average particle size can be measured using a laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., MICROTRAC S3500) and the difference in diffraction pattern according to particle size is measured when the particles pass through a laser beam, thereby calculating the particle size distribution.

[0053] In one embodiment of the present specification, particle size or particle diameter may mean the average diameter or representative diameter of each grain forming the metal powder.

[0054] The terms and words used in this specification should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0055] As used herein, the singular expression of a term includes the plural expression unless the context clearly indicates otherwise.

[0056] The present invention provides a lithium transfer film and a method for manufacturing the same, which can improve the mechanical properties of a substrate layer and thereby suppress or prevent damage to a passivation layer during a transfer process, an electrode for a lithium secondary battery onto which the lithium transfer film is transferred, and a lithium secondary battery including the same.

[0057] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below.

[0058] A lithium transfer film according to one embodiment of the present specification comprises a sequentially laminated substrate layer; a lithium metal layer and a passivation layer, wherein the substrate layer has a Young's modulus in the machine direction (MD) and the transverse direction (TD) of 4.2 GPa or more, an elongation in the MD and the TD of 130% or less, and a deviation of the elongation in the MD and the TD of ±3.5 or less.

[0059] When a lithium transfer film is transferred to an electrode, a pre-lithiated electrode can be manufactured. Here, pre-lithiation is generally performed to solve the problem of low initial efficiency due to lithium consumption in forming SEI and various irreversible phases during initial charging in a lithium secondary battery negative electrode. Before assembling the cell, an amount of lithium equivalent to that consumed is added to the electrode in advance to form an irreversible phase (SEI layer, Li2O, Li x SiO y ) to significantly increase the initial efficiency. In addition, when a lithium transfer film is transferred to an electrode collector such as copper foil, a negative electrode of a lithium metal battery can be formed.

[0060] Lithium-transferred electrodes can be continuously manufactured by applying pressure to one or both sides of the electrode by contacting the lithium transfer film with the substrate through a roll-to-roll process. In this case, during the lithium transfer process using the roll-to-roll process, the lithium transfer film and the electrode, which is the transfer target, are mounted together on the roll-to-roll process equipment and then pulled with a certain tension. If tension is not applied, wrinkles may occur in the electrode during the lithium transfer process, and misalignment may occur between the lithium transfer film and the electrode. However, when the lithium transfer film is pulled due to this tension, the surface oxide layer that prevents lithium oxidation may be broken due to the low physical properties of the substrate layer.

[0061] The above surface oxide layer is a passivation layer formed on one side of the lithium transfer film, and can suppress or prevent lithium loss by suppressing or preventing side reactions caused by the formation of lithium oxide or nitride on the surface of the lithium transfer film, suppressing a sudden reaction between the electrode and the lithium metal layer during the lithium transfer process, suppressing heat generation, and reducing nitriding or oxidation reactions that may promote additional heat generation.

[0062] This passivation layer is a hard but very thin film, so there is a problem that it is easily broken by the application of tension during the roll-to-roll process. In general, lithium metal is highly ductile and soft, and its elastic modulus is on the order of several GPa. Therefore, when the lithium metal layer is deformed during the process, the passivation layer of the lithium oxide thin film (several tens of GPa) with a relatively very high elastic modulus is easily broken. Therefore, in order to suppress deformation of the lithium metal layer during the process, the mechanical properties of the base layer on which the lithium metal layer is formed, such as the strain rate (e.g., elastic modulus and elongation) due to a tensile load, need to be small.

[0063] Accordingly, the lithium transfer film according to one embodiment of the present specification is characterized in that it does not easily stretch when tension is applied, has a strain in all directions of MD (machine direction) and TD (transverse direction) that is small below a certain value, and has a strain deviation for each of MD and TD that is also small below a certain value, thereby suppressing or preventing damage to the passivation layer during a roll-to-roll process.

[0064] A lithium transfer film according to one embodiment of the present specification includes a substrate layer, and the substrate layer can be used without limitation as long as it has the characteristics of being able to withstand process conditions such as high temperature in the step of depositing the lithium metal layer, and suppressing or preventing the problem of reverse peeling in which the lithium metal layer is transferred onto the substrate layer during the winding process for transferring the deposited lithium metal layer.

[0065] Specifically, in one embodiment of the present specification, the substrate layer may be at least one selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polymethyl methacrylate (PMMA), polypropylene, polyethylene, and polycarbonate, and more specifically, may be polyethylene terephthalate (PET) or polyethylene naphthalate (PEN).

[0066] In one embodiment of the present specification, the thickness of the substrate layer may be 1 μm or more and 300 μm or less, and specifically, may satisfy a range of 1 μm or more and 100 μm or less, and more specifically, 1 μm or more and 50 μm or less.

[0067] As the thickness of the above-mentioned substrate layer satisfies the above range, the transfer of lithium metal toward the negative electrode active material layer can occur efficiently, and it has the characteristic of being able to suppress or prevent reverse transfer.

[0068] In one embodiment of the present specification, the Young's modulus of the MD and TD of the substrate layer is each 4.2 GPa or more, and the elongation of the MD and TD is each 130% or less.

[0069] In one embodiment of the present specification, the Young's modulus of the MD and TD of the substrate layer may be 4.2 GPa or more, specifically 4.5 GPa or more, and more specifically 4.6 GPa or more, and the elongation of the MD and TD may be 130% or less, specifically 125% or less, respectively.

[0070] In one embodiment of the present specification, the Young's modulus of the MD and TD of the substrate layer may be 4.2 GPa or more and 8 GPa or less, specifically 4.5 GPa or more and 7 GPa or less, and more specifically 4.6 GPa or more and 6 GPa or less, and the elongation of the MD and TD may be 70% or more and 130% or less, specifically 80% or more and 125% or less, respectively.

[0071] When the substrate layer according to one embodiment of the present specification satisfies the Young's modulus and elongation ranges of each of the MD and TD, it is not easily deformed when a tension of about 10 N to 30 N is applied during the process of transferring the lithium transfer film to an adherend using a roll-to-roll process, and thus damage to the passivation layer can be effectively suppressed.

[0072] In addition, in one embodiment of the present specification, the deviation of MD and TD elongation of the substrate layer is ±3.5 or less.

[0073] In one embodiment of the present specification, the deviation of the MD and TD elongation of the substrate layer may be ±3.5 or less, specifically ±3.3 or less, and more specifically ±3 or less.

[0074] When the substrate layer according to one embodiment of the present specification has the deviation range of the MD and TD elongation, damage to the passivation layer can be suppressed or prevented by not being excessively deformed in only one direction during the roll-to-roll process.

[0075] In particular, even if the MD and TD elongation of each of the substrate layers according to one embodiment of the present specification is 130% or less, if the deviation exceeds the above range, damage to the passivation layer may occur when a high tension (30 N or more) is applied.

[0076] A lithium transfer film according to one embodiment of the present specification includes a lithium metal layer, wherein the lithium metal layer is a layer including lithium metal for prelithiating at least one surface of the electrode active material layer or forming a lithium metal electrode, and a commonly used Li metal foil may be used, but is not limited thereto.

[0077] In one embodiment of the present specification, the thickness of the lithium metal layer may be 0.1 μm or more and 15 μm or less, specifically 0.5 μm or more and 13 μm or less, and more specifically 1 μm or more and 10 μm or less.

[0078] In one embodiment of the present specification, when the thickness of the lithium metal layer satisfies the above range, prelithiation that compensates for irreversible capacity can be achieved, the possibility of complete transfer not occurring due to difficulty in peeling of the lithium metal layer can be reduced, the heat generated during the transfer process can be reduced, and the formation of lithium byproducts that may occur due to excessively long prelithiation reaction time can be suppressed, thereby improving the performance of the electrode.

[0079] In one embodiment of the present specification, a deposition method for depositing the lithium metal layer on the substrate layer may be selected from among physical vapor deposition (PDV) and chemical vapor deposition (CVD), and among the physical vapor deposition methods, thermal evaporation may be mainly used, but is not limited thereto, and various deposition methods used in the art may be used.

[0080] A lithium transfer film according to one embodiment of the present specification includes a passivation layer, and the passivation layer may be present on a surface opposite to a surface where the substrate layer is present, with the lithium metal layer as the center. The passivation layer is a hard and thin inorganic film, and can suppress lithium loss due to side reactions caused by lithium oxide or nitride formed on the surface of the lithium transfer film during the transfer process, and can also reduce the risk of ignition due to nitriding or oxidation reactions.

[0081] In one embodiment of the present specification, the passivation layer may be formed on the surface of the lithium metal layer, and specifically, may be formed by treating the surface of the lithium metal layer with carbon dioxide (CO2) gas, and more specifically, may include at least one of Li2CO3 and Li2O formed by treating the surface of the lithium metal layer with carbon dioxide (CO2) gas.

[0082] That is, in one embodiment of the present specification, the passivation layer may include at least one of Li2CO3 and Li2O.

[0083] In one embodiment of the present specification, the Young's modulus of the passivation layer may be about 5 times or more greater than the Young's modulus of the substrate layer, specifically about 6 times or more greater, and more specifically about 10 times or more greater.

[0084] In one embodiment of the present specification, the thickness of the passivation layer may be 1 nm or more and 200 nm or less, specifically 5 nm or more and 200 nm or less, and more specifically 5 nm or more and 100 nm or less.

[0085] In one embodiment of the present specification, when the thickness of the passivation layer satisfies the above range, the surface of the lithium metal layer can be sufficiently protected, so that oxidation and nitridation reactions of the lithium metal layer can be suppressed, and side effects such as a decrease in the rate of the prelithiation reaction or an increase in electrode resistance can be suppressed or prevented.

[0086] A lithium transfer film according to one embodiment of the present specification may further include a release layer between the substrate layer and the lithium metal layer.

[0087] In one embodiment of the present specification, the release layer may be at least one selected from the group consisting of polycarbonate (PC), polydimethylsiloxane (PDMS), polymethylhydrosiloxane (PMHS), polyimide (PI), polymethylmethacrylate (PMMA), and cycloolefin copolymer (COC), and specifically, may be polymethylmethacrylate (PMMA).

[0088] In one embodiment of the present specification, the thickness of the heterogeneous layer may be 0.05 μm or more and 3 μm or less, and specifically, 0.2 μm or more and 1 μm or less.

[0089] In one embodiment of the present specification, when the thickness of the release layer satisfies the above range, sufficient release force of the lithium metal layer can be secured, and the release layer located on the surface after transfer of the lithium metal layer does not play a role in blocking heat release, so formation of by-products may not be accelerated.

[0090] In one embodiment of the present specification, the release layer can be formed by a coating method, and for example, the coating method can be a method selected from the group consisting of dip coating, spray coating, spin coating, die coating, gravure coating, micro-gravure coating, comma coating, and roll coating, but is not limited thereto, and various coating methods that can be used to form a coating layer in the art can be used.

[0091] In one embodiment of the present specification, the deposition method for depositing the lithium metal layer on the heterostructure layer may be applied in the same manner as the deposition method for depositing the lithium metal layer on the substrate layer.

[0092] FIG. 1 is a diagram showing a laminated structure of a lithium transfer film (60) according to one embodiment of the present specification. Specifically, referring to FIG. 1, the lithium transfer film (60) may have a release layer (62) provided on one surface of a substrate layer (61), a lithium metal layer (63) deposited on one surface of the release layer (62), and a passivation layer (64) formed on one surface of the lithium metal layer (63). Meanwhile, the release layer (62) formed between the substrate layer (61) and the lithium metal layer (63) is optional, and the lithium metal layer (63) may be provided on the substrate layer (61) without the release layer (62), but there is no limitation thereto.

[0093] Figure 2 is a flow chart explaining a method for manufacturing a lithium transfer film (60) according to one embodiment of the present specification.

[0094] A method for manufacturing a lithium transfer film (60) according to one embodiment of the present specification includes, when a release layer (62) is provided between a substrate layer (61) and a lithium metal layer (63), a step (S10) of forming a release layer (62) on one surface of the substrate layer (61); a step (S20) of forming a lithium metal layer (63) on one surface of the release layer (62); and a step (S30) of forming a passivation layer (64) on one surface of the lithium metal layer (63). According to one embodiment of the present invention, the substrate layer (61) has a Young's modulus of MD and TD of 4.2 GPa or more, an elongation of MD and TD of 130% or less, and a deviation of the elongation of MD and TD of ±3.5 or less.

[0095] In the method for manufacturing a lithium transfer film according to one embodiment of the present specification, the contents regarding the substrate layer, lithium metal layer, and passivation layer described above can be applied equally to the substrate layer, lithium metal layer, and passivation layer.

[0096] A method for manufacturing a lithium transfer film (60) according to one embodiment of the present specification includes a step of depositing a lithium metal layer (63) on one surface of a substrate layer (61).

[0097] In the deposition step according to one embodiment of the present specification, the deposition method for depositing the lithium metal layer (63) on the substrate layer (61) as described above may be applied in the same manner, and specifically, the lithium metal layer (63) may be deposited on the substrate layer (61) by a vacuum deposition method (evaporation deposition), and more specifically, the lithium metal layer (63) may be deposited by a vacuum thermal deposition method (thermal evaporation deposition).

[0098] In the step of depositing the lithium metal layer (63) according to one embodiment of the present specification, the deposition device may be variously used as long as it is a deposition device used in the art, and for example, EWK-060 from ULVAC may be used.

[0099] In the step of depositing the lithium metal layer (63) according to one embodiment of the present specification, the deposition speed may be 0.5 m / min or more and 5 m / min or less, specifically 1 m / min or more and 3 m / min or less, and more specifically 2 m / min or more and 2.5 m / min or less.

[0100] A step of supplying a lithium metal layer (63) to a substrate layer (61) may be further included before the step of depositing a lithium metal layer (63) according to one embodiment of the present specification.

[0101] The temperature at the stage where the lithium metal layer (63) is supplied according to one embodiment of the present specification may be 10°C or more and 1,000°C or less, specifically 100°C or more and 800°C or less, and more specifically 300°C or more and 600°C or less.

[0102] In one embodiment of the present specification, the step of depositing the lithium metal layer (63) may be performed after the step of forming a release layer (62) on one surface of the base layer (61).

[0103] Specifically, a method for manufacturing a lithium transfer film (60) according to one embodiment of the present specification may include a step of forming a release layer (62) on one side of a substrate layer (61); and a step of depositing a lithium metal layer (63) on the opposite side of the surface of the release layer (62) where the substrate layer (61) is located.

[0104] In one embodiment of the present specification, the step of forming a release layer (62) on one surface of the substrate layer (61) may be applied in the same manner as the method of forming the release layer (62) described above.

[0105] A method for manufacturing a lithium transfer film (60) according to one embodiment of the present specification includes a step of forming a passivation layer (64) on the opposite side of the surface where the substrate layer (61) of the lithium metal layer (63) is located.

[0106] Specifically, the step of forming the passivation layer (64) may include the step of positioning the substrate layer (61) on which the lithium metal layer (63) is deposited in a vacuum chamber; the step of injecting Ar gas and CO2 gas into the vacuum chamber; and the step of forming the passivation layer (64) on the opposite surface of the surface of the lithium metal layer (63) that the substrate layer (61) is in contact with.

[0107] In one embodiment of the present specification, the pressure of the vacuum chamber in the step of forming the passivation layer (64) is 10 -3 torr Above 10 -1 torr It may be less than or equal to 10, specifically -2 torr Above 10 -1 torr It could be as follows:

[0108] In the step of injecting Ar gas and CO2 gas into the vacuum chamber to form a passivation layer (64) according to one embodiment of the present specification, the Ar gas and CO2 gas may be injected at a volume ratio of 1:10 to 10:1, specifically, may be injected at a volume ratio of 8:2 to 2:8, and more specifically, may be injected at a volume ratio of 8:2 to 1:1.

[0109] In one embodiment of the present specification, in the step of forming the passivation layer (64), after the step of injecting Ar gas and CO2 gas into the vacuum chamber, the step of purging the gas until the vacuum chamber reaches atmospheric pressure, and then processing for 1 to 20 minutes, or 5 to 10 minutes, is further included.

[0110] In one embodiment of the present specification, the step of forming the passivation layer (64) may be performed at any one temperature of 0°C or more and 40°C or less, specifically at any one temperature of 10°C or more and 30°C or less, and more specifically at any one temperature of 20°C or more and 28°C or less.

[0111] In one embodiment of the present specification, the step of forming the passivation layer (64) may be performed at room temperature.

[0112] In one embodiment of the present specification, the electrode intermediate of a lithium secondary battery may be sequentially laminated with an electrode current collector layer; an electrode active material layer; and the above-described lithium transfer film (60), and the passivation layer (64) of the lithium transfer film (60) may face the electrode active material layer of the electrode intermediate.

[0113] The above electrode intermediate is an electrode intermediate for manufacturing a prelithiated electrode, and shows a state in which a lithium transfer film (60) of the present invention is laminated on one surface of a prelithiated electrode active material layer before or while the transfer of the lithium metal layer (63) of the present invention starts on one surface of the electrode active material layer. At this time, the prelithiation reaction may start simultaneously with the start of the transfer of the lithium metal layer (63) on one surface of the electrode active material layer, or the prelithiation reaction may start within several seconds after the start of the transfer.

[0114] In one embodiment of the present specification, the electrode intermediate may be sequentially laminated with an electrode current collector layer; and a lithium transfer film (60) including a substrate layer (61), a lithium metal layer (63), and a passivation layer (64), and the passivation layer (64) of the lithium transfer film (60) may face the electrode current collector layer.

[0115] The above electrode intermediate is an electrode intermediate for manufacturing a negative electrode of a Li-metal electrode, and shows a state in which a lithium transfer film (60) is laminated on one side of the electrode current collector layer in order to transfer a lithium metal layer onto one side of the electrode current collector layer.

[0116] In one embodiment of the present specification, the electrode for a lithium secondary battery may include an electrode active material layer or an electrode current collector layer, and the lithium transfer film described above may be transferred to at least one surface of the electrode active material layer or the electrode current collector layer.

[0117] When the lithium transfer film (60) according to one embodiment of the present specification described above is transferred to at least one side of the electrode active material layer, a prelithiated electrode can be formed, and when it is transferred to at least one side of the electrode current collector layer, a negative electrode of a lithium metal battery can be formed.

[0118] That is, in one embodiment of the present specification, the electrode for the lithium secondary battery may be either a pre-lithiated electrode or a negative electrode of a lithium metal battery.

[0119] In another embodiment of the present specification, the pre-lithiated electrode may be a pre-lithiated negative electrode, and the pre-lithiated negative electrode may include a negative electrode active material layer disposed on at least one surface of a negative electrode current collector. The negative electrode active material layer may include the negative electrode active material. Furthermore, the negative electrode active material layer may further include a thickener.

[0120] FIG. 3 is a diagram showing a laminated structure of a lithium-ion battery negative electrode according to one embodiment of the present specification. Specifically, a negative electrode (100) for a lithium secondary battery including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10) can be confirmed, and FIG. 3 shows that the negative electrode active material layer (20) is formed on one surface of the negative electrode current collector layer (10), but the negative electrode active material layer (20) may be formed on both surfaces of the negative electrode current collector layer (10).

[0121] In one embodiment of the present specification, the negative electrode current collector layer may generally have a thickness of 1 μm to 100 μm. The negative electrode current collector layer is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, the bonding strength of the negative electrode active material may be strengthened by forming fine unevenness on the surface, and the negative electrode current collector layer may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

[0122] In one embodiment of the present specification, the thickness of the negative electrode current collector layer is 1 μm to 100 μm, and the thickness of the negative electrode current collector layer may be 20 μm or more and 50 μm or less. However, the thickness may be modified in various ways depending on the type and purpose of the negative electrode used and is not limited thereto.

[0123] The above negative electrode active material layer (20) can be formed by coating a negative electrode slurry containing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and / or a thickener on at least one surface of the negative electrode current collector layer (10), which means that the negative electrode slurry can be formed by applying the negative electrode slurry to at least one surface of the negative electrode current collector layer (10) and drying and rolling.

[0124] In one embodiment of the present specification, the negative electrode slurry may include a negative electrode active material layer composition including the negative electrode active material, a negative electrode binder, a negative electrode conductive material, and / or a thickener; and a slurry solvent.

[0125] In one embodiment of the present specification, the solid content of the cathode slurry can satisfy 5% or more and 40% or less.

[0126] In another embodiment, the solid content of the cathode slurry can satisfy a range of 5% or more and 40% or less, specifically 7% or more and 35% or less, and more specifically 10% or more and 30% or less.

[0127] The solid content of the above negative electrode slurry may mean the content of the negative electrode active material layer composition included in the negative electrode slurry, and may mean the content of the negative electrode active material layer composition based on 100 parts by weight of the negative electrode slurry.

[0128] When the solid content of the above-mentioned negative electrode slurry satisfies the above range, the viscosity is appropriate when forming the negative electrode active material layer, thereby minimizing particle agglomeration of the negative electrode active material layer composition, thereby enabling the formation of the negative electrode active material layer efficiently.

[0129] In one embodiment of the present specification, the solvent may include those known in the art. For example, the solvent may be water (e.g., distilled water) or NMP (N-methyl-2-pyrrolidone).

[0130] A negative electrode according to one embodiment of the present specification can be formed by coating and drying the negative electrode slurry on one or both sides of a negative electrode current collector layer (10), and the slurry solvent in the negative electrode slurry can be dried through the drying step.

[0131] In one embodiment of the present specification, the negative electrode active material layer (20) includes a negative electrode active material, a negative electrode conductive material, and a negative electrode binder, and the negative electrode active material includes a silicon-based active material, and the silicon-based active material is Si, SiOx (0 <x<2), Si / C 및 Si 합금으로 이루어진 군에서 선택되는 1 이상을 포함하는 것일 수 있다.

[0132] In one embodiment of the present specification, the silicon-based active material is Si and SiOx (0 <x<2)로 이루어진 군에서 선택되는 1 이상을 포함하는 것일 수 있다.

[0133] In one embodiment of the present specification, the negative electrode active material may use pure silicon (Si) as a silicon-based active material. Using pure silicon (Si) as the negative electrode active material may mean that, based on 100 parts by weight of the total negative electrode active material as described above, the negative electrode active material may include pure Si particles that are not combined with other particles or elements in an amount of 60 parts by weight or more, specifically 65 parts by weight or more, and more specifically 70 parts by weight or more, based on 100 parts by weight of the silicon-based active material, and may include 95 parts by weight or less, specifically 90 parts by weight or less, and more specifically 85 parts by weight or less.

[0134] In one embodiment of the present specification, the negative active material is SiOx (0 <x<2)를 실리콘계 활물질로서 사용할 수 있으며, 상기 SiOx (0<x<2)는 상기 실리콘계 활물질 내에서 비정질상의 매트릭스 (matrix)에 해당한다. 상기 SiOx (0<x<2)는 Si 및 SiO2가 일부 포함된 형태일 수 있으며, 상기 Si는 상(phase)을 이루고 있을 수도 있다. 즉, 상기 x는 상기 SiOx (0<x<2) 내에 포함된 Si에 대한 O의 개수비에 해당한다.

[0135] The above silicon-based active material can be formed by heating and vaporizing a mixed powder of Si powder and SiO2 powder, and then depositing the vaporized mixed gas. Specifically, the mixed powder of Si powder and SiO2 powder can be heat-treated at 1400°C to 1800°C or 1400°C to 1600°C under vacuum.

[0136] In one embodiment of the present specification, the SiOx (0) based on a total of 100 parts by weight of the negative electrode active material layer (20) <x<2)를 40 중량부 이상, 구체적으로는 50 중량부 이상, 더욱 구체적으로는 60 중량부 이상을 포함할 수 있으며, 100 중량부 이하, 구체적으로는 90 중량부 이하, 더욱 구체적으로는 80 중량부 이하를 포함할 수 있다. 상기 실리콘계 활물질이 SiOx (0<x<2)를 상기 범위로 포함하는 경우, 리튬 이차 전지의 방전 용량이 개선될 수 있다.

[0137] In one embodiment of the present specification, the negative active material may include a metal impurity.

[0138] The above metal impurity is an impurity that can be included in silicon, and its content can satisfy a range of 0.1 part by weight or less based on 100 parts by weight of the negative electrode active material layer.

[0139] Meanwhile, the average particle diameter (D50) of the silicon-based active material of the present specification may be 5 μm to 10 μm, specifically 5.5 μm to 8 μm, and more specifically 6 μm to 7 μm.

[0140] When the average particle diameter is within the above range, the specific surface area of ​​the particles is within an appropriate range, so that the viscosity of the negative electrode slurry is formed within an appropriate range. Accordingly, the particles constituting the negative electrode slurry are smoothly dispersed. In addition, when the size of the silicon-based active material is greater than the range of the lower limit, the contact area between the silicon particles and the conductive material is excellent due to the composite composed of the conductive material and the binder in the negative electrode slurry, so that the possibility of the conductive network continuing increases, thereby increasing the capacity retention rate. Meanwhile, when the average particle diameter satisfies the above range, excessively large silicon particles are excluded, so that the surface of the negative electrode is formed smoothly, and thus the phenomenon of uneven current density during charge and discharge can be suppressed or prevented.

[0141] In one embodiment of the present specification, the silicon-based active material generally has a characteristic BET specific surface area. The BET specific surface area of ​​the silicon-based active material is preferably 0.01 m 2 / g to 150.0 m 2 / g, more preferably 0.1 m 2 / g to 100.0 m 2 / g, especially preferably 0.2 m 2 / g to 80.0 m 2 / g, most preferably 0.2 m 2 / g to 18.0 m 2 / g. The BET surface area is measured (using nitrogen) according to DIN (German institute for standardization) 66131.

[0142] In one embodiment of the present disclosure, the silicon-based active material may exist in, for example, a crystalline or amorphous form and may not be porous. The Si may be spherical or fragmented particles. The silicon particles may also have a fibrous structure or exist in the form of a silicon-containing film or coating.

[0143] In one embodiment of the present specification, the silicon-based active material may be at least 40 parts by weight based on 100 parts by weight of the total negative electrode active material layer (20).

[0144] In one embodiment of the present specification, the silicon-based active material may be included in an amount of 40 parts by weight or more, specifically 50 parts by weight or more, and more specifically 60 parts by weight or more, based on 100 parts by weight of the total negative electrode active material layer (20), and may be included in an amount of 95 parts by weight or less, specifically 90 parts by weight or less, and more specifically 80 parts by weight or less.

[0145] In the charge / discharge reaction of a lithium secondary battery, lithium released from the positive electrode is inserted into the negative electrode during charging, and desorbed from the negative electrode and returned to the positive electrode during discharge. However, in the case of silicon-based negative electrode active materials, the volume change and surface side reactions are severe, so a large amount of lithium inserted into the negative electrode during the initial charge does not return to the positive electrode, which causes the initial irreversible capacity to increase. If the initial irreversible capacity increases, the battery capacity and cycles decrease rapidly.

[0146] Considering these points, the present invention provides a process for pre-treating the negative electrode before the lithium secondary battery lithium transfer process so that lithium metal can be easily transferred from the transfer laminate during the lithium transfer process in the lithium secondary battery lithium transfer process and lithium in the negative electrode active material layer (20) can be uniformly lithium transfered.

[0147] Previously, graphite compounds were typically used solely as anode active materials. However, with the increasing demand for high-capacity batteries, attempts to mix silicon-based compounds to increase capacity have been increasing. However, silicon-based compounds have limitations in that their volume rapidly expands during the charge / discharge process, damaging the conductive path formed within the anode active material layer and lowering battery performance. Therefore, the type of anode conductive material used together with the silicon-based active material is important.

[0148] Accordingly, in one embodiment of the present specification, the negative electrode conductive material may include at least one selected from the group consisting of a planar conductive material, a linear conductive material, and a dot-shaped conductive material, and specifically, may include at least one selected from the group consisting of a planar conductive material and a linear conductive material.

[0149] In one embodiment of the present specification, the negative electrode conductive material may be 1 part by weight or more and 40 parts by weight or less based on 100 parts by weight of the total negative electrode active material layer.

[0150] Specifically, in the above embodiment, the negative electrode conductive material may be included in an amount of 1 part by weight or more and 40 parts by weight or less, specifically 5 parts by weight or more and 30 parts by weight or less, and more specifically 10 parts by weight or more and 25 parts by weight or less, based on 100 parts by weight of the total negative electrode active material layer.

[0151] When the content of the negative electrode conductive material satisfies the above range, there is an effect of not damaging the conductive path formed within the negative electrode active material layer.

[0152] In one embodiment of the present specification, the planar conductive material used as the aforementioned negative electrode conductive material has a structure and function different from those of carbon-based active materials generally used as negative electrode active materials. Specifically, the carbon-based active material used as the negative electrode active material may be artificial graphite or natural graphite, and refers to a material processed into a spherical or dot-shaped form to facilitate the storage and release of lithium ions.

[0153] On the other hand, the planar conductive material used as the negative electrode conductive material is a material having a planar or plate-like shape, and can be expressed as plate-like graphite. In other words, it refers to a material included to maintain a conductive path within the negative electrode active material layer (20), and is not a material that plays a role in storing and releasing lithium, but rather a material that secures a conductive path in the form of a plane within the negative electrode active material layer (20).

[0154] That is, in one embodiment of the present specification, the use of plate-shaped graphite as a conductive material means that it is processed into a planar or plate-shaped form and used as a material that secures a conductive path rather than a role of storing or releasing lithium. In this case, the included negative electrode active material has high capacity characteristics for lithium storage and release, and plays a role of storing and releasing all lithium ions transferred from the positive electrode.

[0155] On the other hand, in one embodiment of the present specification, the use of a carbon-based active material as an active material means that it is processed into a dot or spherical shape and used as a material that plays a role in storing or releasing lithium.

[0156] In one embodiment of the present specification, the negative conductive material may include a planar conductive material.

[0157] In one embodiment of the present specification, the planar conductive material refers to a conductive material having a two-dimensional (2D) structure in which atoms form a crystal structure on a plane with a thickness of a single atomic layer or multiple atomic layers of two or more layers. The planar conductive material refers to a material for securing a conductive path in a planar shape within a negative electrode active material layer, and at the same time, can play a role in suppressing disconnection of the conductive path due to volume expansion, and can be expressed as a plate-shaped conductive material or a bulk-shaped conductive material.

[0158] In one embodiment of the present specification, the planar conductive material may include at least one selected from the group consisting of plate-shaped graphite, graphene, graphene oxide, and graphite flakes, and may preferably be plate-shaped graphite.

[0159] In one embodiment of the present specification, the average particle diameter (D50) of the planar conductive material may be 2 μm to 7 μm, specifically 3 μm to 6 μm, and more specifically 4 μm to 5 μm. When the above range is satisfied, due to sufficient particle size, dispersion is easy without causing excessive viscosity increase of the negative electrode slurry, and the dispersion effect is excellent when dispersion is performed using the same equipment and time.

[0160] In one embodiment of the present specification, the surface-shaped conductive material may have a D10 of 0.5 μm or more and 1.7 μm or less, a D50 of 2.5 μm or more and 3.5 μm or less, and a D90 of 6.8 μm or more and 15.0 μm or less.

[0161] In one embodiment of the present specification, the planar conductive material may be a high-specific surface area planar conductive material having a high BET surface area; or a low-specific surface area planar conductive material.

[0162] In one embodiment of the present specification, a high surface area surface conductive material or a low surface area surface conductive material may be used without limitation as the surface conductive material; however, since the surface conductive material according to the present specification may be affected to some extent by dispersion effects on electrode performance, a low surface area surface conductive material that does not cause dispersion problems may be used.

[0163] In one embodiment of the present specification, the surface-shaped conductive material has a BET specific surface area of ​​5 m 2 / g or more than 500m 2 / g or less, specifically 5m 2 / g or more than 300m 2 / g or less, more specifically 5m 2 / g or more than 250m 2 / g can be less.

[0164] In another embodiment, the surface-shaped conductive material is a high surface area surface-shaped conductive material, and has a BET surface area of ​​50 m 2 / g or more than 500m 2 / g or less, specifically 80m 2 / g or more than 300m 2 / g or less, more specifically 100m 2 / g or more than 300m 2 / g can satisfy the range below.

[0165] In another embodiment, the surface-shaped conductive material is a low surface area surface-shaped conductive material, and has a BET surface area of ​​5 m 2 / g or more than 40m 2 / g or less, specifically 5m 2 / g or more than 30m 2 / g or less, more specifically 5m 2 / g or more than 25m 2 / g can satisfy the range below.

[0166] In one embodiment of the present specification, the negative electrode conductive material may include a linear conductive material. The linear conductive material refers to a conductive material having a one-dimensional (1D) structure with a diameter in the nanometer order and a high aspect ratio, or a conductive material having a fibrous structure such as a cylindrical type or a tube type. Examples of the linear conductive material include carbon nanotubes, and the carbon nanotubes may be bundle-type carbon nanotubes. The bundle-type carbon nanotubes may include a plurality of carbon nanotube units. Here, unless otherwise stated, the term "bundle type" refers to a secondary shape in the form of a bundle or rope in which a plurality of carbon nanotube units are arranged in a parallel manner or entangled with the longitudinal axes of the carbon nanotube units in substantially the same orientation. The above carbon nanotube unit has a graphite sheet in the shape of a cylinder with a nano-sized diameter, and sp 2It has a bonding structure. At this time, depending on the angle and structure at which the graphite plane is rolled, it can exhibit the characteristics of a conductor or semiconductor. Compared to entangled type carbon nanotubes, the bundled carbon nanotubes can be uniformly dispersed during the manufacture of the cathode, and can smoothly form a conductive network within the cathode, thereby improving the conductivity of the cathode.

[0167] In one embodiment of the present specification, the negative electrode conductive material may preferably include at least one selected from the group consisting of plate-like graphite, single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs), but is not limited thereto.

[0168] In one embodiment of the present specification, the linear conductive material has a BET specific surface area of ​​100 m 2 / g or more than 10,000m 2 / g or less, specifically 500m 2 / g or more than 5,000m 2 / g or less, more specifically 1,000m 2 / g or more than 1,500m 2 / g can be less.

[0169] In addition, in one embodiment of the present specification, the aspect ratio of the linear conductive material may be 500 or more, specifically 1,000 or more, more specifically 10,000 or more, and may be 1,000,000 or less, specifically 100,000 or less.

[0170] In one embodiment of the present specification, when the linear conductive material satisfies the BET specific surface area and aspect ratio range, it has the effect of suppressing electrical short-circuiting between the negative electrode active materials.

[0171] In one embodiment of the present specification, the cathode conductive material may further include a dot-shaped conductive material.

[0172] In one embodiment of the present specification, the dot-shaped conductive material refers to a conductive material having a zero-dimensional (0D) structure in which a crystal lump composed of 1 to several hundred atoms is shaped like a round ball and has a volume. The dot-shaped conductive material can be used to improve conductivity in a cathode, and refers to a conductive material having conductivity without causing a chemical change. Specifically, the dot-shaped conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, conductive fiber, fluorocarbon, aluminum powder, nickel powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivatives, and preferably, it may include carbon black in terms of implementing high conductivity and excellent dispersibility.

[0173] In one embodiment of the present specification, the dot-shaped conductive material has a BET specific surface area of ​​40 m 2 / g or more than 70m 2 / g or less, specifically 45m 2 / g or more than 65m 2 / g or less, more specifically 50m 2 / g or more than 60m 2 / g can be less.

[0174] In one embodiment of the present specification, the particle size of the dot-shaped conductive material may be 10 nm to 100 nm, specifically 20 nm to 90 nm, and more specifically 20 nm to 60 nm.

[0175] The negative electrode conductive material according to this specification has a completely separate composition from the conductive material applied to the positive electrode. The negative electrode conductive material according to this specification serves to secure the contact between silicon-based active materials, which undergo significant volume expansion of the electrode due to charging and discharging, and is completely different in composition and function from the positive electrode conductive material, which acts as a buffer during rolling and provides some conductivity.

[0176] In addition, the negative electrode conductive material according to the present specification is applied to a silicon-based negative electrode active material and has a completely different composition from the conductive material applied to a graphite-based active material. The conductive material used in an electrode having a graphite-based active material simply has smaller particles than the active material, and thus has the characteristics of improving output characteristics and imparting some conductivity, and thus has a different composition and role from the negative electrode conductive material applied together with a silicon-based negative electrode active material as in the present invention.

[0177] In one embodiment of the present specification, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyacrylamide, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and a material in which hydrogens thereof are substituted with Li, Na, Ca, or the like, and may also include various copolymers thereof.

[0178] The negative electrode binder according to one embodiment of the present specification serves to hold the active material and the conductive material in order to suppress or prevent distortion and structural deformation of the negative electrode structure in the expansion and relaxation of the volume of the silicon-based active material, and a general binder satisfying the above role can be applied, and specifically, it can include one or more binders selected from the group consisting of polyacrylamide (PAM) and styrene butadiene rubber.

[0179] In one embodiment of the present specification, the negative electrode binder may be included in an amount of 30 parts by weight or less, specifically 20 parts by weight or less, and more specifically 10 parts by weight or less, based on a total of 100 parts by weight of the negative electrode active material layer (20), and may be included in an amount of 1 part by weight or more or 3 parts by weight or more.

[0180] In one embodiment of the present invention, the weight average molecular weight of the binder may be 100,000 g / mol or more and 1,500,000 g / mol or less.

[0181] When the weight-average molecular weight of the binder satisfies the above range, the electrode exhibits excellent mechanical strength and high intermolecular interaction, resulting in superior electrode adhesion. Furthermore, when the above range is met, the binder viscosity can be appropriately selected, which can further improve the coating properties of the electrode when used to manufacture a cathode.

[0182] Another embodiment of the present specification according to the method for manufacturing the lithium-ion negative electrode may be formed by transferring the lithium transfer film to at least one surface of the negative electrode active material layer (20).

[0183] The method for manufacturing a prelithiated negative electrode according to the present specification is characterized by performing prelithiation on at least one side of a negative electrode active material layer to improve Coulomb efficiency by solving the irreversibility problem of a silicon-based electrode, and performing prelithiation by a lithium transfer method with high mass productivity because the process speed is faster than prelithiation by a SLMP (Stabilized Lithium Metal Powder) method or an electrochemical method.

[0184] In one embodiment of the present specification, the step of forming a prelithiated negative electrode by transferring the aforementioned lithium transfer film to at least one surface of the negative electrode active material layer (20) includes the step of contacting the lithium transfer film so that the lithium metal layer faces at least one surface of the negative electrode active material layer; and the step of applying pressure.

[0185] In one embodiment of the present specification, the step of contacting the lithium transfer film with at least one surface of the negative electrode active material layer (20) so that the lithium metal layer (63) faces the surface is a step for transferring the negative electrode active material layer (20) to lithium metal.

[0186] In one embodiment of the present specification, the pressurizing step can more actively promote the transfer of the negative electrode active material layer (20) to the negative electrode, and has the effect of forming the negative electrode thin despite having a high energy density.

[0187] At this time, the lithium transfer film (60) is positioned so that the lithium metal layer (63) of the lithium transfer film (60) is in contact with one or both sides of the negative active material layer (20), and then a load of 10 kgf to 500 kgf is applied and a transfer process can be performed through roll pressing. Thereafter, a process of removing the substrate layer or the release layer and substrate layer may be included.

[0188] In one embodiment of the present specification, the step of removing the substrate layer (61) or the release layer (62) and the substrate layer (61) of the lithium transfer film (60) may be performed after the lithium metal layer (63) and the negative electrode active material layer (20) are brought into contact with each other and transferred by applying pressure.

[0189] In a method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present specification, prelithiation may proceed from the moment the lithium metal layer (63) of the lithium transfer film (60) comes into contact with the negative electrode active material layer (20), prelithiation may proceed from the step of pressurizing, and prelithiation may proceed from the step of removing the substrate layer or the release layer and substrate layer.

[0190] In another embodiment of the present specification, the negative electrode of the lithium metal battery may include a negative electrode current collector having the lithium transfer film (60) described above transferred on at least one side.

[0191] At this time, the above-described method for transferring the negative electrode current collector and lithium transfer film (60) can be applied.

[0192] A lithium secondary battery according to one embodiment of the present specification may include an electrode for a lithium secondary battery according to one embodiment described above. Specifically, the secondary battery may include an electrode for a lithium secondary battery, a separator, and an electrolyte, and the electrode for a lithium secondary battery may be a negative electrode or a positive electrode.

[0193] FIG. 4 is a diagram showing a laminated structure of a lithium secondary battery using a prelithiated electrode according to one embodiment of the present specification. Specifically, the laminated structure of the lithium secondary battery includes a lithium secondary battery negative electrode (100) including a negative electrode active material layer (20) on one surface of a negative electrode current collector layer (10), and a lithium secondary battery positive electrode (200) including a positive electrode active material layer (40) on one surface of a positive electrode current collector layer (50), and the lithium secondary battery negative electrode (100) and the lithium secondary battery positive electrode (200) are shown to be formed in a structure in which they are laminated with a separator (30) interposed therebetween.

[0194] The above positive electrode may include a positive electrode current collector layer and a positive electrode active material layer formed on at least one surface of the positive electrode current collector layer, and including the positive electrode active material.

[0195] In the above positive electrode, the positive electrode current collector layer is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector layer may typically have a thickness of 3 μm to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector layer to increase the adhesion of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0196] According to one embodiment of the present specification, the positive electrode active material may include at least one selected from the group consisting of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, lithium aluminum oxide, or a lithium composite oxide comprising these.

[0197] Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤c2≤0.5); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); or LiMn2O4 in which a portion of Li in the chemical formula is replaced with an alkaline earth metal ion; but is not limited thereto. The positive electrode may be Li-metal.

[0198] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0199] At this time, the positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used.

[0200] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0201] The solvent used in the positive electrode composition slurry may be a solvent generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or as a mixture of two or more. The amount of the solvent used is sufficient to dissolve or disperse the active material, conductive material, and binder in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive and negative electrodes. In addition, as another method, the positive and negative electrodes may be manufactured by casting the composition for forming the active material layer on a separate support, and then laminating the film obtained by peeling it from the support on a current collector.

[0202] The separator above separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, it can have low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can be used. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0203] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0204] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0205] As the above non-aqueous organic solvent, for example, aprotic solvents such as N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, and ethyl propionate Organic solvents may be used.

[0206] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts. In addition, when low-viscosity, low-dielectric constant linear carbonates such as dimethyl carbonate and diethyl carbonate are mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte having high electrical conductivity can be produced, so that they can be used even more preferably.

[0207] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte, for example, the anion of the lithium salt is F - , Cl - , I - , NO3- , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0208] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, difluoroethylene carbonate and other haloalkylene carbonate compounds, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery.

[0209] One embodiment of the present specification provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0210] In addition, another embodiment of the present specification provides a battery pack including the lithium secondary battery.

[0211] The lithium secondary battery according to the embodiments of the present specification stably exhibits excellent discharge capacity, output characteristics, and cycle performance, and therefore can be used as a power source for portable devices such as mobile phones, laptop computers, and digital cameras, as well as medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. For example, the battery module or battery pack can be used as a power source for any one or more medium- to large-sized devices selected from the group consisting of power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0212] Hereinafter, preferred embodiments are presented to help understand the present invention, but the above embodiments are only illustrative of the present disclosure, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended patent claims.

[0213]

[0214] <Manufacturing Example>

[0215] Example 1

[0216] <Manufacturing of Lithium Transfer Film>

[0217] A transfer film was prepared in which an acrylic resin (release layer) was coated 1 μm thick on a PET A substrate layer. At this time, the PET A used was polyethylene terephthalate that satisfies the mechanical properties shown in Table 1 below.

[0218] Lithium was deposited on the acrylic resin coating layer of the above-mentioned transfer film by thermal evaporation deposition to form a lithium layer with a thickness of 6 μm. The deposition device used was ULVAC's EWK-060, and the deposition process was performed at a speed of 2.5 m / min, a temperature of the lithium supply section of 500°C, and a temperature of the main roll of -25°C.

[0219] The manufactured transfer film is placed in the chamber, and 10 -1 After the chamber vacuum was made below 10 torr, the vacuum valve was closed, the gas purge valve was opened, and argon (Ar) gas and carbon dioxide (CO2) gas were injected into the chamber at a volume ratio of 8:2 at room temperature, and each gas was purged until the vacuum of the chamber became atmospheric pressure. After processing for about 10 minutes, a lithium transfer film was manufactured in which a passivation layer containing Li2CO3 was formed on the surface of the deposited lithium thin film.

[0220] Example 2

[0221] A lithium transfer film was manufactured in the same manner as in Example 1, except that PEN (polyethylene naphthalate) having the mechanical properties shown in Table 1 below was used as the substrate layer.

[0222] Comparative Example 1

[0223] A lithium transfer film was manufactured in the same manner as in Example 1, except that PET B having the mechanical properties shown in Table 1 below was used as the substrate layer.

[0224] Comparative Example 2

[0225] A lithium transfer film was manufactured in the same manner as in Example 1, except that PET C having the mechanical properties shown in Table 1 below was used as the substrate layer.

[0226] Comparative Example 3

[0227] A lithium transfer film was manufactured in the same manner as in Example 1, except that PET D having the mechanical properties shown in Table 1 below was used as the substrate layer.

[0228] Comparative Example 4

[0229] A lithium transfer film was manufactured in the same manner as in Example 1, except that PET E having the mechanical properties shown in Table 1 below was used as the substrate layer.

[0230] Comparative Example 5

[0231] A lithium transfer film was manufactured in the same manner as in Example 1, except that PET F having the mechanical properties shown in Table 1 below was used as the substrate layer.

[0232] The mechanical properties of the substrate layers used in Examples 1 and 2 and Comparative Examples 1 to 5 were measured under room temperature conditions using the tensile test method of ASTM D882 and are summarized in Table 1 below.

[0233] <Experimental Example>

[0234] If a passivation layer is not formed on the surface of a lithium transfer film, the surface is rapidly nitrided due to a nitridation reaction in a nitrogen environment (an environment controlled to <10 ppm of oxygen and moisture). Therefore, this phenomenon was used to confirm whether the passivation layer on the surface of the lithium transfer film was damaged.

[0235] In a chamber having two shafts capable of applying tension to enable unwinding / rewinding of a film roll, the lithium transfer films of Examples 1 and 2 and Comparative Examples 1 to 5 manufactured according to the above manufacturing example were placed on the shafts inside the chamber, and the inside of the chamber was purged with nitrogen for 30 minutes. Afterwards, the inside of the chamber was circulated for 30 minutes with a purifier, and when the oxygen and moisture concentrations became 10 ppm or less, tensions of 10 N and 30 N were applied to each lithium transfer film, and after 10 minutes, whether or not the surface of the lithium metal layer was nitrided was observed, which is shown in Table 1 below. 'X' means that no nitridation reaction occurred, and 'O' means that nitridation reaction occurred. Since the surface of the lithium metal layer turns black when nitridation reaction occurs, whether or not there is a nitridation reaction can be observed with the naked eye.

[0236] Example 1 (PET A) Example 2 (PEN) Comparative Example 1 (PET B) Comparative Example 2 (PET C) Comparative Example 3 (PET D) Comparative Example 4 (PET E) Comparative Example 5 (PET F) Elongation (%) MD 1 2 2.5 9 0.2 1 3 9.7 1 2 6.0 1 3 3.8 1 2 1.0 1 0 7.8 TD 1 1 9.2 8 5.5 1 4 0.5 1 3 7.1 1 3 6.7 1 4 8.0 1 2 9.8 Elongation deviation 1.7 2.4 0.4 5.6 1.4 5 13.5 1 1.0 Young's Modulus (GPa)MD4.685.214.304.423.914.744.56TD5.165.644.704.724.194.554.19Nitriding reaction depending on tension size10NXXXXOOX30NXXOOOOO

[0237] As can be confirmed in Table 1 above, the lithium transfer film of Comparative Example 1 did not satisfy the characteristic mechanical properties of the present specification, as the MD and TD elongations of the substrate layer were each 130% or more, and it was confirmed that the passivation layer was damaged under a high tension condition of 30 N during the roll-to-roll process, and a nitriding reaction occurred on the lithium surface.

[0238] Similarly, the lithium transfer film of Comparative Example 2 had a TD elongation of the substrate layer of 130% or more, and MD and TD elongation deviations exceeding ±3.5, and thus did not have the characteristic mechanical properties of the present specification, and it was confirmed that a nitriding reaction occurred on the lithium surface under high tension conditions of 30 N.

[0239] In Comparative Example 3, since the elongation and Young's modulus of the MD and TD of the original were not satisfied, a nitriding reaction was observed even under a relatively low tension condition of 10 N. Comparative Example 4 is similar to Comparative Example 2, but the elongation deviation greatly increased, and a nitriding reaction was observed even under a low tension condition of 10 N due to damage to the passivation layer.

[0240] In Comparative Example 5, although the range of elongation and Young's modulus was satisfactory, the Young's modulus of TD was small and the deviation was unsatisfactory, so a nitriding reaction was observed under a tension condition of 30 N.

[0241] However, the present invention Examples 1 and 2 use a substrate layer that satisfies all the conditions of having a Young's modulus of 4.2 GPa or more in MD and TD, an elongation of 130% or less in MD and TD, and a deviation of elongation of MD and TD of ±3.5 or less, so that it does not easily elongate due to tension application regardless of the tension size, and has a low strain in either the MD or TD axis, so that damage to the passivation layer can be prevented during a roll-to-roll lithium transfer process, thereby suppressing or preventing the lithium surface from being nitrided or oxidized.

[0242] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

[0243]

[0244] [Explanation of symbols]

[0245] 10: Negative current collector layer

[0246] 20: Negative active material layer

[0247] 30: Membrane

[0248] 40: Positive active material layer

[0249] 50: Positive current collector layer

[0250] 60: Lithium transfer film

[0251] 61: Substrate layer

[0252] 62: Heterogeneous layer

[0253] 63: Lithium metal layer

[0254] 64: Passivation layer

[0255] 100: Cathode for lithium secondary batteries

[0256] 200: Cathode for lithium secondary batteries

Claims

1. A substrate layer; a lithium metal layer; and a passivation layer, A lithium transfer film, wherein the above-mentioned substrate layer has a Young's modulus of 4.2 GPa or more in the MD (machine direction) and TD (transverse direction), an elongation in the MD and TD is 130% or less, and a deviation in the elongation in the MD and TD is ±3.5 or less.

2. In claim 1, A lithium transfer film, wherein the passivation layer comprises at least one of Li2CO3 and Li2O.

3. In claim 1, A lithium transfer film, wherein the thickness of the lithium metal layer is 1 μm or more and 10 μm or less.

4. In claim 1, A lithium transfer film, wherein the thickness of the passivation layer is 5 nm or more and 200 nm or less.

5. In claim 1, A lithium transfer film further comprising a heterostructure layer between the substrate layer and the lithium metal layer.

6. A step of depositing a lithium metal layer on one surface of the substrate layer; and A step of forming a passivation layer on the opposite surface of the surface on which the substrate layer of the lithium metal layer is located, A method for manufacturing a lithium transfer film, wherein the Young's modulus of the MD and TD of the above-mentioned substrate layer is 4.2 GPa or more, the elongation of the MD and TD is 130% or less, and the deviation of the elongation of the MD and TD is ±3.5 or less.

7. In claim 6, The step of forming the above passivation layer is A step of positioning the substrate layer on which the lithium metal layer is deposited in a vacuum chamber; A step of injecting Ar gas and CO2 gas into the vacuum chamber; and A method for manufacturing a lithium transfer film, comprising the step of forming a passivation layer on the opposite surface of the surface of the lithium metal layer to which the substrate layer is in contact.

8. In claim 6, The step of depositing the above lithium metal layer is A method for manufacturing a lithium transfer film, the method comprising: forming a release layer on one side of the substrate layer; 9. Electrode current collector layer; Electrode active material layer; and A lithium transfer film according to any one of claims 1 to 5 is sequentially laminated, An electrode intermediate in which the passivation layer of the lithium transfer film faces the electrode active material layer.

10. Electrode current collector layer; and A lithium transfer film according to any one of claims 1 to 5 is sequentially laminated, An electrode intermediate in which the passivation layer of the lithium transfer film faces the electrode current collector layer.

11. Containing an electrode active material layer or an electrode current collector layer, An electrode for a lithium secondary battery, wherein a lithium transfer film according to any one of claims 1 to 5 is transferred to at least one surface of the electrode active material layer or the electrode current collector layer.

12. In claim 11, The above electrode active material layer includes a silicon-based active material, and the silicon-based active material is Si, SiOx (0 <x<2), Si / C 및 Si 합금으로 이루어진 군에서 선택되는 1 이상을 포함하는 것인 리튬 이차 전지용 전극.

13. In claim 11, An electrode for a lithium secondary battery, wherein the electrode active material layer includes a negative electrode conductive material, and the negative electrode conductive material includes at least one selected from the group consisting of plate-shaped graphite, single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs).

14. An electrode for a lithium secondary battery according to claim 11; Membrane; and A lithium secondary battery containing an electrolyte.

15. A battery module comprising a lithium secondary battery according to claim 14.

16. A battery pack comprising a lithium secondary battery according to claim 14.

17. A battery pack comprising a battery module according to claim 15.

Images