Electrode for a negative electrode battery having an oxide-based solid electrolyte protective layer and lithium secondary battery containing the same

Abstract

The present invention relates to an electrode and a secondary battery that can ensure the electrodeposition / desorption stability of lithium in a lithium secondary battery and prevent the formation of lithium dendritic structures and internal short circuits. The electrode for the non-negative electrode battery includes a negative electrode current collector and a negative electrode protective layer located on the negative electrode current collector, the negative electrode protective layer may include oxide-based solid electrolyte particles.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority rights based on Korean Patent Application No. 10-2023-0163656 dated November 22, 2023, and Korean Patent Application No. 10-2024-0161137 dated November 13, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein as part of this specification.

[0002] This invention relates to an electrode for a non-negative electrode battery that can improve the stability of lithium electrodeposition / desorption behavior, and to a lithium secondary battery containing the same. [Background technology]

[0003] Recently, as the application areas of lithium-ion batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, communications, and computers to power storage and supply for large-area devices such as automobiles and energy storage devices, there is a growing demand for lithium-ion batteries that are high-capacity, high-output, long-life, and highly stable.

[0004] Lithium metal secondary batteries are batteries that use lithium metal (Li-metal) material as the negative electrode active material, and theoretically have the advantage of having much higher energy density and capacity compared to existing batteries that use graphite-based or lithium alloy-based negative electrodes. Therefore, research and development of such lithium metal secondary batteries are ongoing because they can be applied to batteries that require high energy density.

[0005] However, lithium metal secondary batteries have a problem in that, due to the properties of lithium metal, the negative electrode active material, the volume change of the negative electrode is very large during the charging / discharging process, and the lithium generated during charging grows into a needle-like shape, forming lithium dendrites. If the growth of such lithium dendrites continues, they can penetrate the separator membrane and cause a short circuit in the cell, which can result in significant problems with battery performance or safety issues such as fire.

[0006] On the other hand, in the lithium metal secondary battery described above, when lithium metal is used as the negative electrode active material, it has high reactivity with the electrolyte, so irreversible reactions may continuously occur during the charge / discharge process. The surface film formed by such irreversible reactions not only has the problem that it collapses due to large volume changes during charge and discharge, causing additional irreversible reactions, but also the continuous irreversible reactions can reduce the Coulombic efficiency of the cell and cause the problem of overall degradation of cell performance.

[0007] To address the problems caused by continuous irreversible reactions on the lithium metal surface and suppress the drawbacks resulting from the major disadvantages of such lithium metal negative electrodes, including the disadvantage caused by lithium dendrite growth, researches and attempts have been continuously made to form a negative electrode protective layer on the surface of a lithium metal negative electrode by applying various materials and methods from the past. [Summary of the Invention] [Problem to be Solved by the Invention]

[0008] Therefore, an object of the present invention is to provide an electrode for an anode-free battery that can solve the sudden death problem caused by lithium dendritic growth and internal short circuit due to non-uniform ion distribution at the copper current collector interface. More specifically, the present invention aims to ensure the stability of lithium deposition / delamination behavior, delay the decomposition of solvents and salts, and solve the lifetime problem caused by lithium dendritic formation and internal short circuit. [Means for Solving the Problem]

[0009] Hereinafter, an electrolyte composition for a lithium metal battery according to specific embodiments of the present invention and the like will be described.

[0010] Terms and words used in the present specification and claims should not be construed as being limited to ordinary or dictionary meanings. Based on the principle that an inventor can appropriately define the concept of terms in order to describe his or her own invention in the best way, they should be construed with meanings and concepts consistent with the technical idea of the present invention.

[0011] The terms used in the present specification are used only for describing exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0012] In the present specification, terms such as "comprising", "including" or "having" are intended to specify that the recited features, numbers, steps, components, or combinations thereof exist, and it should be understood that these terms do not exclude in advance the existence or possibility of addition of one or more other features, numbers, steps, components, or combinations thereof.

[0013] In addition, as used herein, the term "anode-free battery" may refer to a secondary battery that, in a state before charge and discharge, for example, in a state immediately after production, does not have a separate anode active material layer such as a lithium metal layer, a lithium alloy layer, or another carbon-containing layer on an anode current collector, wherein the anode current collector includes, for example, a conductive metal layer such as copper and a metal oxide layer having a large work function. Accordingly, the "anode-free battery" can be defined as a battery in which the anode is formed of the anode current collector in a state before charge and discharge, and does not include a separate anode active material layer or a lithium metal layer on the anode current collector. However, it goes without saying that, other than the anode active material layer or the lithium metal layer, addition of a separate insulating layer or other thin film that does not participate in the movement of lithium ions and / or electrons during charge and discharge is not limited.

[0014] In addition, the term "anode-free battery" shall not be construed as limiting the presence of a lithium-containing cathode active material, or limiting the presence of a lithium metal layer or a lithium-containing compound that grows on the anode current collector through performing charge and discharge.

[0015] Electrode for Anode-Free Battery According to one embodiment of the present invention, an electrode for a negative electrode battery is provided, comprising a negative electrode current collector; and a negative electrode protective layer located on the negative electrode current collector; wherein the negative electrode protective layer comprises oxide-based solid electrolyte particles, the oxide-based solid electrolyte particles satisfying an average diameter of 0.02–10 μm and a particle size distribution span (span) < 1. The electrode for the negative electrode battery can ensure the stability of lithium electrodeposition / desorption behavior by applying a negative electrode protective layer located on the negative electrode current collector and containing oxide-based solid electrolyte particles, thereby controlling the distribution of lithium ions and the electrolyte structure at the interface of the metal current collector during charging / discharging.

[0016] In exemplary embodiments, the negative electrode current collector may be made of platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), copper (Cu), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In-doped SnO2), FTO (F-doped SnO2), and alloys thereof, as well as copper (Cu) or stainless steel surface-treated with carbon (C), nickel (Ni), titanium (Ti), or silver (Ag), but is not necessarily limited thereto. The negative electrode current collector may take the form of foil, film, sheet, punched, porous, foam, or the like.

[0017] In exemplary embodiments, the negative electrode protective layer may further include a conductive material. The conductive material can improve the active surface area of ​​the lithium nuclide. Specifically, the conductive material may include one or more selected from the group consisting of carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a well-developed crystalline structure; and conductive nanomaterials such as graphene, carbon nanofibers, or carbon nanotubes. For example, the conductive material may include spherical carbon black or plate-shaped graphene.

[0018] In exemplary embodiments, the oxide-based solid electrolyte particles may satisfy an average diameter of 0.02–10 μm and a particle size distribution span < 1. For example, the oxide-based solid electrolyte particles may be in the ranges of 0.05 μm or more, 0.1 μm or more, 0.2 μm or more, and 5.0 μm or less, 3.0 μm or less, 1.0 μm or less, 0.5 μm or less, 0.4 μm or less, and 0.3 μm or less. Preferably, they can have an average diameter range of 0.1 μm to 1.0 μm, 0.1 to 0.5 μm, or 0.2 to 0.4 μm. On the other hand, if the particle size distribution span < 1 range is exceeded, the coating of the negative electrode protective layer may not be properly performed.

[0019] Specifically, the oxide-based solid electrolyte particles can have a uniform particle size distribution with a specific average diameter and a span of 1 or less. Experimental results by the inventors show that by including oxide-based solid electrolyte particles that satisfy a specific particle size distribution within the electrode protective layer, the ion distribution at the metal current collector interface can be made uniform.

[0020] Furthermore, the oxide-based solid electrolyte particles may show a single peak in the 0.1 to 1.0 μm region through particle size distribution (PSD) analysis. If the oxide-based solid electrolyte particles are not sufficiently dispersed and aggregate, they may have a bimodal distribution with double peaks. In this case, cracks or performance imbalances may occur during drying after slurry application.

[0021] In an exemplary embodiment, the oxide-based solid electrolyte may have a sample variance of 0.04 or less, as shown in EDS analysis, represented by the following formula 1.

[0022]

number

[0023] Here, S 2 is the sample variance, y is the variation factor.

[0024]

number

[0025] ∫ is the sample mean, n is the sample size, SS is the sum of squared deviations, and df is the degrees of freedom.

[0026] For example, the sample dispersion may be 0.04 or less, or 0.03 or less. If the sample dispersion exceeds 0.04, uniform dispersion of the oxide-based solid electrolyte cannot be guaranteed, which may result in a failure to guarantee the stability of lithium electrodeposition / desorption behavior.

[0027] Specifically, the sample variance can be calculated using Equation 1, which assumes that pixel information from the EDS Ti and / or P element mapping image has been extracted and divided into n uniform grids, each set as a sample. The sample variance value indicates the distribution of the degree of dispersion of Ti and P between each grid, and a smaller sample variance value means that the elements of Ti and P are uniformly distributed in the overall grid. Therefore, a smaller sample variance value indicates that the oxide-based solid electrolyte (LATP) in the electrode protective layer is even more uniformly distributed.

[0028] On the other hand, the sample variance can be obtained by analyzing the distribution of oxide-based solid electrolyte (LATP) within the electrode based on the mapping images of the Ti and P elements of the oxide-based solid electrolyte (LATP) from the SEM and EDS analysis results of the electrode cross-section. Specifically, the data was extracted and converted into an access file format based on the pixel information of the EDS Ti and P element mapping images. The extracted data may be divided into a grid of 50 × 23, totaling 1150 grids, and set as samples, and the sample variance of Ti and P elements may be calculated.

[0029] In exemplary embodiments, the oxide-based solid electrolyte can be any solid electrolyte that contains lithium in its structure and has a lithium ion source, and is in the form of a lithium metal oxide or lithium metal phosphorus oxide.

[0030] Specific examples include one or more lithium metal oxides or lithium metal phosphoroxides selected from Nasicon-type solid electrolytes, Lisicon-type solid electrolytes, Garnet-type solid electrolytes, Perovskite-type solid electrolytes, and LiPON-type solid electrolytes. More specifically, examples include one or more compounds selected from the group consisting of LAGP (lithium aluminum germanium phosphate) compounds, LLZO (lithium lanthanum zirconium oxide) compounds, LATP (lithium aluminum titanium phosphate) compounds, LLZTO (lithium lanthanum zirconium tantalum oxide) compounds, LLTO (lithium lanthanum titanium oxide) compounds, LSTP (lithium silicon titanium phosphate) compounds, and LGPO (lithium germanium phosphate) compounds.

[0031] Among these, a non-conyson solid electrolyte such as the LAGP-based compound or LATP-based compound can be appropriately used from the viewpoint of uniformly distributing lithium ions at the interface of the current collector.

[0032] In exemplary embodiments, the negative electrode protective layer may further include a binder. The binder may be a component that assists in the bonding of oxide-based solid electrolyte particles and other materials to the current collector. Typically, the binder is a component that assists in the bonding of active material and conductive materials and other materials to the current collector in the negative electrode protective layer, and may be added in an amount of 1 to 30% by weight based on the total weight of solids in the negative electrode slurry. It is added in an amount of 1 to 50 parts by weight, more specifically 3 to 15 parts by weight, based on the total weight of solids in the negative electrode slurry. If the amount of binder is less than 1 part by weight, the adhesion between the electrode active material and the current collector may be insufficient, and if it exceeds 50 parts by weight, the adhesion improves, but the amount of electrode active material decreases accordingly, which may result in a lower battery capacity.

[0033] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-dientelpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0034] In exemplary embodiments, the negative electrode protective layer may have a thickness of 1 to 10 μm. While a thickness range exceeding 10 μm may be advantageous in delaying internal short circuits due to lithium dendritic formation, it may degrade battery performance in terms of maximizing resistance in terms of ion conduction.

[0035] In exemplary embodiments, the oxide-based solid electrolyte particles may be present in an amount of 50 to 95% by weight relative to the total weight of the negative electrode protective layer. When the oxide-based solid electrolyte particles are present within the range described above, the stability of lithium electrodeposition / desorption behavior can be improved, and in particular, when the amount is less than 50% by weight, the effect of adding the oxide-based solid electrolyte may be insufficient.

[0036] On the other hand, a method for manufacturing electrodes for a negative electrode battery is provided, which includes the steps of: preparing a solid electrolyte dispersion by mixing and dispersing an oxide-based solid electrolyte and a solvent; and applying the solid electrolyte dispersion onto an electrode current collector to form an electrode protective layer.

[0037] In an exemplary embodiment, the step of preparing the solid electrolyte dispersion can be carried out using a bead-milling method. By first dispersing the oxide-based solid electrolyte and solvent prior to the formation of the electrode protective layer, the oxide-based solid electrolyte particles can be uniformly distributed within the electrode protective layer.

[0038] Lithium-ion rechargeable battery According to another embodiment of the present invention, a lithium secondary battery is provided comprising a positive electrode; a negative electrode; and an electrolyte comprising a lithium salt and a non-aqueous organic solvent, wherein the electrode for a non-negative electrode battery described above is used as the negative electrode. In such another embodiment of the present invention, an electrode protective layer comprising oxide-based solid electrolyte particles and a conductive material is applied to ensure the stability of lithium electrodeposition / desorption behavior by controlling the distribution of lithium ions and the electrolyte structure at the interface of the copper current collector during charging / discharging, thereby delaying the decomposition of the solvent and salt, and solving the lifespan problems caused by lithium dendritic formation and internal short circuits.

[0039] In exemplary embodiments, the negative electrode may not include a negative electrode active material layer and may include only a negative electrode current collector. In such a negative electrode, during the charge-discharge process, lithium ions that have moved from the positive electrode can be electrodeposited onto the negative electrode current collector to form a lithium metal layer, and such a lithium metal layer can act as the negative electrode active material.

[0040] On the other hand, a positive electrode for a lithium secondary battery according to an exemplary embodiment can be manufactured, for example, by mixing and dispersing the positive electrode active material, oxide-based solid electrolyte, binder, and conductive material in a dispersion medium (solvent) to create a slurry, applying this slurry to a metal current collector, and then drying and rolling it. In this case, the dispersion medium can be, but is not limited to, NMP (N-methyl-2-pyrrolidone), DMF (Dimethyl formamide), DMSO (Dimethyl sulfoxide), ethanol, isopropanol, water, and mixtures thereof.

[0041] In exemplary embodiments, the system may further include a separation membrane interposed between the positive and negative electrodes, or the electrolyte may be in the form of an electrolyte membrane or electrolyte film containing the lithium salt and a non-aqueous organic solvent within a polymer matrix and interposed between the positive and negative electrodes.

[0042] The lithium secondary battery of the other embodiment described above includes an electrolyte containing a lithium salt and a non-aqueous organic solvent. Such an electrolyte acts as a transmission medium for lithium ions between the positive electrode and the negative electrode, and such lithium ions exist in the electrolyte in a solvated state, and may be inserted into the electrode active material after undergoing desolvation at the interface between the electrolyte and the electrode.

[0043] The lithium salt contained in the electrolyte is used as a medium for transmitting ions in a lithium secondary battery. The lithium salt contains, for example, Li as a cation + , and contains F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH -CF3(CF2)7SO3 - and SCN - It may also contain anions selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 It may contain one or more selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2, and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2).

[0044] The concentration of the lithium salt can be appropriately changed within a range that is normally usable, and may be included in the electrolyte at a concentration of 0.5 M to 6 M, or 1 M to 5 M.

[0045] In a more specific embodiment, the electrolyte may contain lithium salt at a relatively low concentration of 0.5 M to less than 2 M, or 0.7 M to 1.5 M. Even in such cases, as the desolvation of lithium ions is accelerated by the action of the electrode in the aforementioned embodiment, the lithium secondary battery of the other embodiment can exhibit improved output characteristics. As a result, problems such as increased electrolyte viscosity, decreased fluidity, and decreased ionic conductivity of the electrolyte and battery output at low temperatures, which occur when applying electrolyte compositions containing high concentrations of lithium salt, can be solved, and excellent low-temperature characteristics of the lithium secondary battery can be achieved.

[0046] On the other hand, by applying an electrode for a lithium-ion battery according to one embodiment, lithium-ion conductivity can be improved and resistance reduced even at low temperatures. This reduces the deterioration of low-temperature power characteristics caused by high-concentration lithium salts, etc.

[0047] On the other hand, the type of non-aqueous organic solvent that may be included in the electrolyte is not particularly limited, and any organic solvent that has been known to be applicable to electrolytes for lithium-ion batteries can be used. Examples of such organic solvents include one or more selected from the group consisting of carbonate-based solvents, ether-based solvents, nitrile-based solvents, phosphate-based solvents, and sulfone-based solvents.

[0048] More specifically, the carbonate-based solvent can be dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, methyl propyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate, or methyl (2,2,2-trifluoroethyl) carbonate, and the phosphate-based solvent can be trimethyl phosphate, triethyl phosphate, or 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphosphorane 2-oxide.

[0049] Furthermore, as the ether-based solvent, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, or tetrahydrofuran derivatives such as 2-methyltetrahydrofuran can be used, and as the nitrile-based solvent, succinonitrile, adiponitrile, sebaconitrile, acetonitrile, or propionitrile can be used. Furthermore, as the sulfone-based solvent, dimethyl sulfone, ethyl methyl sulfone, or sulforane can be used.

[0050] On the other hand, the electrolyte may further contain, in addition to the lithium salt and non-aqueous organic solvent described above, a diluent that exhibits solubility in the lithium salt that is 10 times or less less than that of the non-aqueous organic solvent. Such a diluent may be an organic solvent that is substantially insoluble in the lithium salt but miscible with the non-aqueous organic solvent, for example, an ether-based solvent having a fluorine-substituted alkyl group, and more specifically, one or more selected from the group consisting of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), bis-2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynononafluorobutane (MOFB), and ethoxynononafluorobutane (EOFB).

[0051] When such a diluent is further included, locally high concentrations of lithium salt may be present in the non-aqueous organic solvent within the electrolyte, while lithium salt may be substantially absent in the diluent. In this way, the presence of locally high concentrations of lithium salt in a solvated form within the electrolyte can further improve the output characteristics of the lithium secondary battery and reduce the increase in viscosity and decrease in fluidity of the electrolyte. In addition, when such a locally high-concentration salt electrolyte is applied together with the electrode of one embodiment, lithium ion conductivity can be improved and resistance reduced even at low temperatures, thereby suppressing the decrease in low-temperature output characteristics caused by high-concentration lithium salts, etc.

[0052] The amount of the diluent used can be adjusted according to the type of non-aqueous organic solvent and lithium salt, and the overall concentration of the lithium salt. For example, the diluent may be included in the electrolyte in a content such that the molar ratio of the diluent to the non-aqueous organic solvent is 1:0.2 to 1:5, or 1:0.5 to 1:2.

[0053] On the other hand, the lithium secondary battery of the other embodiments described above may further include a porous separator membrane interposed between the positive electrode and the negative electrode.

[0054] Such porous separation membranes can be made from polyethylene, olefin polymers such as polypropylene, glass fibers, etc., in the form of sheets, multilayer membranes, fine porous films, woven fabrics, and nonwoven fabrics, but are not necessarily limited to these forms. However, it may be preferable to use porous polyethylene or porous glass fiber nonwoven fabric (glass filter) as the separation membrane, and it may be even more preferable to use porous glass fiber nonwoven fabric (glass filter) as the separation membrane. The separation membrane may be a thin, insulating film with high ion permeability and mechanical strength, and the pore diameter of the separation membrane may generally be in the range of 0.01 to 10 μm, and the thickness may generally be in the range of 5 to 300 μm, but are not limited to these.

[0055] Furthermore, in another example of the lithium secondary battery, the separation membrane may not be present, and the aforementioned electrolyte may be interposed between the positive and negative electrodes in the form of an electrolyte membrane or electrolyte film. In this case, the electrolyte membrane or electrolyte film may be in the form of a polymer matrix containing the aforementioned lithium salt and a non-aqueous organic solvent, and a well-known polymer-based solid electrolyte may be used as the polymer matrix. In such a case, the lithium secondary battery of the other embodiment may be a semi-solid battery that uses both a liquid electrolyte and a solid electrolyte.

[0056] On the other hand, lithium secondary batteries of the other embodiments described above can be manufactured by conventional methods of the art. For example, an electrode assembly including a positive electrode, a negative electrode, and a separator membrane (or electrolyte membrane) can be housed in a case and manufactured by injecting and impregnating the aforementioned electrolyte.

[0057] Such lithium secondary batteries can be applied not only to battery cells used as power sources for small devices, but are also particularly suitable for use as unit batteries in battery modules that power medium- and large-sized devices. [Effects of the Invention]

[0058] The electrode for a negative electrode-less battery of the present invention is located on a negative electrode current collector, and by applying a negative electrode protective layer containing oxide-based solid electrolyte particles, it is possible to ensure the stability of lithium electrodeposition / desorption behavior through control of lithium ion distribution and electrolyte structure at the interface of the metal current collector during charging / discharging.

[0059] Furthermore, it can delay the decomposition of the solvent and salt, and solve the lifespan problems caused by lithium dendritic formation and internal short circuits. [Brief explanation of the drawing]

[0060] [Figure 1] The voltage change due to area capacity is shown for batteries to which the electrodes of Examples 1-2 and Comparative Examples 1-2 are applied. [Figure 2] The voltage change due to area capacity is shown for batteries to which the electrodes of Examples 1-2 and Comparative Examples 1-2 are applied. [Figure 3] The voltage change due to area capacity is shown for batteries to which the electrodes of Examples 1-2 and Comparative Examples 1-2 are applied. [Figure 4] The voltage change due to area capacity is shown for batteries to which the electrodes of Examples 1-2 and Comparative Examples 1-2 are applied. [Figure 5] The polarization level change due to cycling is shown in batteries to which the electrodes of Examples 1-2 and Comparative Examples 1-2 are applied. [Figure 6] The Coulomb efficiency by cycle is shown for batteries using electrodes from Examples 1-2 and Comparative Examples 1-2. [Figure 7] The measurement results for the particle size distribution (PSD) of the oxide-based solid electrolyte LATP in the electrode according to Example 1 are shown. [Figure 8] The measurement results for the particle size distribution (PSD) of the oxide-based solid electrolyte LATP in the electrode according to Comparative Example 2 are shown. [Figure 9] The results of EDS analysis for the electrode according to Example 1 are shown. [Modes for carrying out the invention]

[0061] The following describes in detail embodiments of the present invention so that those with ordinary skill in the art to which the invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0062] Example 1: LATP protective layer electrode D50: LiAl (300nm) 0.3 Ti 1.7 10 g of (PO4)3 oxide-based solid electrolyte (LATP), a PVdF binder (PVdF:LATP weight ratio of 10:90), and 90 g of NMP were mixed. After placing a bead mill into the mixture, a dispersion treatment was performed for 40 minutes using a spike mill to produce a solid electrolyte nanoparticle dispersion. Subsequently, the solid electrolyte nanoparticle dispersion was sprayed onto a Cu current collector and dried to form an 8 μm thick protective layer, thereby producing an electrode for a non-negative electrode battery having an LATP protective layer.

[0063] Example 2: LATP & CNT protective layer electrode D50:300nm LiAl 0.3 Ti 1.7 An electrode for a negative electrode battery having an LATP & CNT protective layer was manufactured in the same manner as in Example 1, except that 50 g of (PO4)3 oxide-based solid electrolyte (LATP), a PVdF binder (PVdF:LATP weight ratio: 10:90), 50 g of CNT, and 50 g of NMP were mixed.

[0064] Comparative example 1: Bare electrode A copper current collector (SK Nexilons, 8 μm) was used.

[0065] Comparative example 2: Span=3.883 electrode An electrode for a negative electrode battery having an LATP protective layer was manufactured in the same manner as in Example 1, except that a 40-minute dispersion treatment was not performed using a spike mill. On the other hand, it was confirmed that cracks formed on the protective layer during the drying process after the application of the negative electrode protective layer to the manufactured electrode.

[0066] Experimental Example 1: Measurement Results of Particle Size Distribution (PSD) A Malvern Mastersizer was used to confirm the particle size distribution of the oxide-based solid electrolyte LATP in the electrodes of Example 1 and Comparative Example 2. The results are shown in graphs 7 and 8. Referring to Figure 7, a single peak was observed around 0.2 to 0.3 μm. This confirmed that the average diameter and particle size distribution of 0.02-10 μm, and span < 1, were satisfied for Example 1.

[0067] In contrast, referring to Figure 8, in the case of Comparative Example 2, a double peak was observed, measured at D10:0.454μm, D50:0.827μm, D90:3.66μm, D99:5.18μm, and D100:5.91μm, confirming a particle size distribution span:3.883 and a span > 1.

[0068] Experimental Example 2: Analysis of EDS Based on the SEM and EDS analysis results of the electrode cross-section in Example 1, the distribution of the oxide-based solid electrolyte (LATP) within the electrode was analyzed based on the mapping images of the O, Ti, and P elements of the oxide-based solid electrolyte LATP, and the results are shown in Figure 9.

[0069] First, the pixel information of the EDSO, Ti, and P element mapping images was converted and extracted into an Accel file format. The extracted data was divided into 1150 grids of 50 × 23 pixels each, and the sample variances for O, Ti, and P were calculated. The specific sample variances were obtained using Equation 1 below.

[0070]

number

[0071] Here, S 2 is the sample variance, y is the variation factor.

[0072]

number

[0073] ∫ is the sample mean, n is the sample size, SS is the sum of squared deviations, and df is the degrees of freedom.

[0074] As a result, it can be confirmed that the sample variance value for Example 1 is 0.04 or less.

[0075] Experimental Example 3: Lithium Electrodeposition Behavior Coin cells were manufactured using the electrodes from Examples 1-2 and Comparative Examples 1-2. Specifically, a Cu positive electrode (Cu coated with LATP can also be used), a separation membrane, and a gasket were stacked in that order on the bottom of the coin cell, and then the electrolyte was applied. After that, a lithium metal negative electrode, a 1 mm thick spacer, and a spring were placed in that order, and then the cell was sealed by closing it with a cap and applying a constant pressure.

[0076] 1) The assembled coin cell is set to 0.5 mAcm². -2 Apply with a current density of 1 mAh cm -2 The lithium was electrodeposited onto copper to achieve a capacitance per unit area, and when stripping the electrodeposited lithium, a 1V cutoff was performed at the same current density.

[0077] Figures 1-4 show the voltage change due to areal capacity in batteries using electrodes from Examples 1-2 and Comparative Examples 1-2. While it was expected that the Li electrodeposition overpotential would decrease during space charge region formation in the experiments, it was confirmed that the initial nucleation overpotential increased in all cases with the introduction of the electrode protection layer. This is presumed to be due to the diffusivity of the initial bulk.

[0078] 2) Referring to Figure 5, the overvoltage between the charge / discharge curves was measured in the intermediate flat region, excluding the initial and final stages, under the experimental conditions described in Figures 1-4 above.

[0079] Figure 5 shows the change in polarization level with cycles in batteries using electrodes from Examples 1-2 and Comparative Example 1. The results confirmed that the efficiency improved with an increased number of electrodeposition / desorption cycles when the electrode protective layer was introduced, and that the polarization level between electrodeposition and desorption decreased. In particular, Comparative Example 2, which has a span > 1 range, was found to have the highest polarization level. This improved the lifespan characteristics through the electrode protective layer, especially in relation to the capacity realization rate.

[0080] 3) Next, the charge-discharge efficiency was measured. In this experiment, the charge-discharge efficiency is the ratio of electrodeposited amount to desorption amount, and can be expressed by the following formula.

[0081] [Formula 2] Charge / discharge efficiency (%) = Desorption amount | Electrodeposition amount × 100 Figure 6 shows the lithium electrodeposition / desorption efficiency by cycle in batteries using electrodes from Examples 1-2 and Comparative Examples 1-2. As a result, it was confirmed that the introduction of a protective layer enabled desorption of up to 95% of the electrodeposition amount, and this efficiency was improved by approximately 10% compared to Comparative Example 1.

Claims

1. Negative electrode current collector; and Includes a negative electrode protective layer located on the negative electrode current collector; The negative electrode protective layer comprises oxide-based solid electrolyte particles, The oxide-based solid electrolyte particles satisfy an average diameter of 0.02–10 μm and a particle size distribution span (span) < 1, and are electrodes for a negative electrode battery.

2. The negative electrode protective layer further comprises a conductive material, The electrode for a non-negative electrode battery according to claim 1, wherein the conductive material is one or more selected from the group consisting of carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, natural graphite, artificial graphite, graphite, graphene, carbon nanofibers, and carbon nanotubes.

3. The electrode for a non-negative battery according to claim 1, wherein the oxide-based solid electrolyte particles exhibit a single peak in the 0.1 to 1.0 μm region through particle size distribution (PSD) analysis.

4. The oxide-based solid electrolyte particles, as determined by EDS analysis, have a sample variance of 0.04 or less, as shown in the following formula 1, for the electrode for a negative electrode battery according to claim 1: [Math 1] Here, S ２ is the sample variance, y is the variation factor. [Math 2] ∫ is the sample mean, n is the sample size, SS is the sum of squared deviations, and df is the degrees of freedom.

5. The electrode for a non-negative electrode battery according to claim 1, wherein the oxide-based solid electrolyte of the oxide-based solid electrolyte particles comprises one or more compounds selected from the group consisting of LAGP (lithium aluminum germanium phosphate) compounds, LLZO (lithium lanthanum zirconium oxide) compounds, LATP (lithium aluminum titanium phosphate) compounds, LLZTO (lithium lanthanum zirconium tantalum oxide) compounds, LLTO (lithium lanthanum titanium oxide) compounds, LSTP (lithium silicon titanium phosphate) compounds, and LGPO (lithium germanium phosphate) compounds.

6. The electrode for a non-negative battery according to claim 1, wherein the negative electrode protective layer has a thickness of 1 to 20 μm.

7. The electrode for a negative electrode battery according to claim 1, wherein the oxide-based solid electrolyte particles are contained in an amount of 50 to 95% by weight relative to the total weight of the negative electrode protective layer.

8. A positive electrode; a negative electrode; and an electrolyte comprising a lithium salt and a non-aqueous organic solvent; A lithium secondary battery comprising, as a negative electrode, an electrode for a non-negative battery as described in any one of claims 1 to 7.

9. The lithium salt is selected from the group consisting of LiCl, LiBr, LiI, LiBF ４ , LiClO ４ , LiB １０ Cl １０ , LiAlCl ４ , LiAlO ２ , LiPF ６ , LiCF ３ SO ３ , LiCH ３ CO ２ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiCH ３ SO ３ , LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO ２ F) ２ ), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO ２ CF ２ CF ３ ) ２ and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO ２ CF ３ ) ２ ), and the lithium secondary battery according to claim 8, which comprises one or more selected from the group consisting of the above.

10. The invention further includes a separation membrane interposed between the positive and negative electrodes, The lithium secondary battery according to claim 8, wherein the electrolyte has the form of an electrolyte membrane or electrolyte film containing the lithium salt and a non-aqueous organic solvent within a polymer matrix, and is interposed between the positive electrode and the negative electrode.

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