All-solid-state batteries containing prelithiated silicon anodes

Abstract

The present invention relates to a negative electrode for an all-solid-state battery and an all-solid-state battery including the negative electrode. More specifically, the present invention relates to a prelithiated silicon negative electrode, an all-solid-state battery including the same, and a method for manufacturing the same.

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Application No. 63 / 518,274, filed August 8, 2023, U.S. Regular Application No. 18 / 470,746, filed September 20, 2023, and Korean Patent Application No. 10-2024-0105593, filed August 7, 2024, the entire contents of which are expressly incorporated herein by reference.

[0002] The present invention relates to a negative electrode for an all-solid-state battery and an all-solid-state battery including the negative electrode. More specifically, the present invention relates to a prelithiated silicon negative electrode, an all-solid-state battery including the same, and a method for manufacturing the same. [Background technology]

[0003] Conventional lithium-ion secondary batteries use transition metal oxide-based positive electrode active materials and carbon-based negative electrode active materials, and use a liquid electrolyte to ensure lithium ion conductivity between the positive and negative electrodes. However, the carbon-based negative electrode active materials have low lithium ion storage capacity, limiting their ability to increase charging capacity.

[0004] Recently, there has been increasing research into high-capacity anode active materials such as silicon (Si) as an alternative to carbon-based anode active materials. Silicon (Si) has high electrical conductivity and exhibits higher capacity characteristics than carbon-based active materials. Therefore, when silicon (Si) is used as an anode active material, it is possible to achieve higher battery capacity and smaller battery size compared to batteries using carbon-based anode active materials.

[0005] However, silicon (Si) undergoes large volume changes during charging and discharging, which makes it prone to cracking. When new surfaces are exposed through the cracks and come into contact with liquid electrolytes, a solid electrolyte interphase (SEI) film forms on the surface, causing irreversible reactions and low efficiency, resulting in reduced energy density and lifespan. To prevent this problem, various Si nanostructures have been considered for use in silicon (Si) anodes together with carbon compounds and binder materials to prevent decomposition.

[0006] However, despite such continuous research, it remains difficult to demonstrate high first cycle coulombic efficiency and excellent life performance of the cells, and a new approach is needed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Publication No. 2006-0056969 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an all-solid-state battery that uses silicon (Si) as a negative electrode active material.

[0009] Another object of the present invention is to provide an all-solid-state battery that is excellent in electrochemical properties such as energy density, life characteristics, and coulombic efficiency.

[0010] It will be readily apparent that other objects and advantages of the present invention can be achieved by the means or methods recited in the claims and combinations thereof. [Means for solving the problem]

[0011] One aspect of the present invention relates to an all-solid-state battery including a negative electrode, a positive electrode, and a sulfide-based solid electrolyte interposed between the negative electrode and the positive electrode, wherein the negative electrode includes a negative electrode active material layer containing silicon (Si), and the negative electrode is prelithiated and includes an interface layer between the solid electrolyte and the negative electrode active material layer.

[0012] In one embodiment of the present invention, the sulfide-based solid electrolyte is an argyrodite-based sulfide-based solid electrolyte (Li6PS5X; X=Cl, Br, I).

[0013] In one embodiment of the present invention, the interface layer is made of one or more selected from Li2S, LiX (X: Cl, Br, or I), and Li3P.

[0014] In one embodiment of the present invention, after charging the all-solid-state battery, the content of LiS, LiX (X: Cl, Br, or I) or LiP in the interface layer is 1 to 50 mol % based on 100 mol % of the total content of the solid electrolyte and the interface layer.

[0015] In one embodiment of the present invention, the negative electrode active material layer contains 0.25 mol to 2 mol of lithium per 1 mol of silicon.

[0016] In one aspect of the present invention, the silicon is composed of a plurality of silicon particles, and the silicon particles have a particle size of 0.1 μm to 10 μm.

[0017] In one embodiment of the present invention, when the all-solid-state battery is discharged after multiple charge-discharge cycles, the content of lithium remaining in the negative electrode active material layer is 0.1 mol or more based on 1 mol of silicon.

[0018] In one embodiment of the present invention, the negative electrode active material layer may further include a conductive material.

[0019] In one aspect of the present invention, the positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a lithium transition metal composite oxide, and the transition metal includes one or more of Co, Mn, Ni, and Al.

[0020] In one aspect of the present invention, the lithium transition metal composite oxide includes at least one or more of the compounds represented by the following Chemical Formula 1: [Chemical Formula 1] Li x Ni a Co b Mn c M z O y In Chemical Formula 1, 0.5 ≦ x ≦ 1.5, 0 ≦ a ≦ 1, 0 ≦ b < 1, 0 ≦ c < 1, 0 ≦ z < 1, 1.5 < y < 5, a + b + c + z is 1 or less, and M includes one or more selected from Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge, and Sn.

Advantages of the Invention

[0021] The all-solid-state battery according to the present invention can provide a battery with a high energy density and an increased life performance by including a pre-lithiated silicon negative electrode.

[0022] In addition, the negative electrode can provide an all-solid-state battery with a high initial conductivity and an initial efficiency.

Brief Description of the Drawings

[0023] [Figure 1] It is a diagram showing the initial conductivity of the pre-lithiated silicon negative electrode according to the present invention and the negative electrode of the comparative example. [Figure 2] It is a diagram showing the phase change between the lithium metal phase and the pre-lithiated silicon during the manufacturing process of the pre-lithiated silicon negative electrode according to the present invention. [Figure 3] It is a diagram showing a comparison of the initial efficiency of the all-solid-state battery according to the present invention and the battery of the comparative example. [Figure 4] FIG. 10 is a graph showing a comparison of life characteristics between the all-solid-state battery according to the present invention and a battery of a comparative example. [Figure 5] FIG. 1 is a graph showing the capacity retention rate and coulomb efficiency of an all-solid-state battery according to the present invention and a battery of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will now be described in detail. Prior to this, the terms and words used in the specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as having meanings and concepts consistent with the technical concept of the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention. Therefore, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical concept of the present invention, and therefore, at the time of filing this application, various equivalents and modifications may exist that can replace them.

[0025] Throughout this specification, when a part "comprises" or "includes" certain elements, this does not mean that other elements are excluded, but that other elements may also be included, unless otherwise specified.

[0026] Furthermore, the terms "about," "substantially," and the like used throughout this specification are used to mean a numerical value or a value close to that numerical value when inherent manufacturing and material tolerances are given, and are used to prevent unscrupulous infringers from unfairly using disclosure content in which precise or absolute numerical values ​​are mentioned to facilitate understanding of this application.

[0027] Throughout this specification, the phrase "A and / or B" means "A or B, or both."

[0028] The present invention relates to an all-solid-state battery containing a solid electrolyte material as an electrolyte. Specific examples of the all-solid-state battery include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitors. In particular, the secondary battery is specifically a lithium-ion secondary battery.

[0029] In one embodiment, the all-solid-state battery according to the present invention comprises a negative electrode, a positive electrode, and a sulfide-based solid electrolyte interposed between the negative electrode and the positive electrode, wherein the negative electrode comprises a negative electrode active material layer containing silicon (Si) as a negative electrode active material, and the negative electrode is prelithiated.

[0030] When lithium metal is used as an anode, it has high energy density and long life characteristics, but at low operating temperatures, lithium dendrites grow in depth, resulting in degradation of battery performance. However, silicon anodes are not susceptible to lithium dendrite growth and therefore exhibit excellent performance even at room temperature, making them more advantageous than lithium metal anodes. Meanwhile, in batteries using liquid electrolytes, silicon anodes exhibit excellent high-rate charging characteristics at low operating temperatures (e.g., below room temperature), but have low reversible areal capacities. This is because it is difficult to incorporate high-loading electrodes into liquid electrolyte batteries. The battery according to the present invention has the advantage of being able to solve the above-mentioned problems.

[0031] The configuration and effects of the present invention will be described in detail below.

[0032] In one embodiment of the present invention, the negative electrode includes a negative electrode active material layer containing silicon, and the negative electrode may be pre-lithiated.

[0033] Here, prelithiation means that before assembling the battery, by further supplying the anode with just enough lithium to be consumed during the electrochemical cycle, the amount of lithium ions that can be reversibly used is conserved, maximizing the energy density of the battery with a high-capacity anode.

[0034] The anode active material layer containing silicon may be any anode containing elemental silicon, a silicon alloy, or a silicon compound.

[0035] The elemental silicon may be single-crystalline silicon, polycrystalline silicon, amorphous nanosilicon, etc.

[0036] As silicon alloys, alloys containing at least one selected from tin, aluminum, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium and having a second element other than silicon can be mentioned.

[0037] As silicon compounds, compounds containing oxygen and carbon can be mentioned, and the silicon compounds may contain, in addition to silicon, elements selected from tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium.

[0038] Embodiments of silicon alloys and compounds include SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiO v (0 < v ≤ 2), SnO w (0 < w ≤ 2), LiSiO, etc.

[0039] The anode may contain other anode active materials such as graphite in addition to silicon.

[0040] In one embodiment of the present invention, the silicon may be composed of a plurality of silicon particles, and the silicon particles may have a particle size of 0.1 μm to 10 μm.

[0041] In one embodiment of the present invention, the lithium used in the prelithiated negative electrode may be lithium powder, lithium oxide powder, lithium carbide powder, or lithium nitride powder.

[0042] The lithium content in the pre-lithiated silicon negative electrode may be 3 to 33 wt % based on the total weight of the negative electrode. Specifically, the lithium content in the pre-lithiated silicon negative electrode may be 3 wt % or more, 3.5 wt % or more, 4 wt % or more, 4.5 wt % or more, 5 wt % or more, 5.5 wt % or more, 6 wt % or more, 6.5 wt % or more, 7 wt % or more, 7.5 wt % or more, 8 wt % or more, or 33 wt % or less, 32.5 wt % or less, 32 wt % or less, 31.5 wt % or less, 31 wt % or less, 30.5 wt % or less, 30 wt % or less, 29.5 wt % or less, or 29 wt % or less, based on the total weight of the negative electrode.

[0043] The lithium content in the prelithiated silicon negative electrode may be 0.25 mol to 2 mol based on 1 mol of silicon (Si). Specifically, the lithium content in the prelithiated silicon negative electrode may be 0.25 mol or more, 0.30 mol or more, 0.35 mol or more, 0.40 mol or more, 0.45 mol or more, 0.50 mol or more, 0.55 mol or more, 0.60 mol or more, 0.65 mol or more, 0.70 mol or more, 0.75 mol or more, 0.80 mol or more, 0.85 mol or more, 0.90 mol or more, or 2.0 mol or less based on 1 mol of silicon. It may be 1.95 mols or less, 1.90 mols or less, 1.85 mols or less, 1.80 mols or less, 1.75 mols or less, 1.70 mols or less, 1.65 mols or less, 1.60 mols or less, 1.55 mols or less, 1.50 mols or less, 1.45 mols or less, 1.40 mols or less, 1.35 mols or less, 1.30 mols or less, 1.25 mols or less, 1.20 mols or less, 1.15 mols or less, 1.10 mols or less, 1.05 mols or less, or 1.0 mols or less.

[0044] FIG. 2 shows the phase changes of lithium metal and prelithiated silicon during the process of manufacturing a prelithiated silicon anode according to the present invention. Specifically, in the process of manufacturing the anode, after mixing lithium metal powder and silicon, the pressure and time of pressure were changed to confirm whether actual prelithiated silicon was formed. Lithium solid-state NMR ( 7 As a result of confirmation through Li Solid state NMR, it was confirmed that as the pressurization pressure and pressurization time increased, the lithium metal phase decreased and the prelithiated silicon phase increased.

[0045] In one embodiment of the present invention, the initial conductivity of the negative electrode active material layer may be increased as the lithium content per mole of silicon (Si) increases. FIG. 1 is a graph showing the initial conductivity of a pre-lithiated silicon negative electrode according to the present invention and a comparative negative electrode. The initial conductivity of the pre-lithiated silicon negative electrode according to the present invention is 1.0×10 -3 S / cm to 1.0×10 S / cm.

[0046] In one embodiment of the present invention, the initial efficiency of the negative electrode active material layer may be higher as the lithium content per mole of silicon (Si) increases. Figure 3 is a graph comparing the initial efficiency of an all-solid-state battery according to the present invention with a battery of a comparative example. The initial efficiency of the all-solid-state battery according to the present invention may be 90% or more and 99% or less.

[0047] In one embodiment of the present invention, the negative electrode active material layer may include a conductive material. In particular, the conductive material may be a carbon-based conductive material such as carbon black. When the negative electrode active material layer includes a conductive material, the content of the conductive material may be less than 1.0 wt %. If the content of the conductive material exceeds 1.0 wt %, the irreversible decomposition reaction of the solid electrolyte may be accelerated, resulting in a decrease in the resistance characteristics and lifespan of the battery.

[0048] In one embodiment of the present invention, the negative electrode active material layer may be composed only of silicon (Si) and lithium, or may further include a binder resin in addition to the silicon (Si) and lithium. In this case, the binder resin may be included in an amount of less than 10 wt %, less than 1 wt %, or less than 0.1 wt %, based on 100 wt % of the negative electrode active material layer.

[0049] The negative electrode may include a negative electrode current collector, and the negative electrode active material layer may be formed on at least one surface of the current collector. In one embodiment of the present invention, the negative electrode active material layer may have a thickness of about 10 μm to 100 μm, for example, 10 μm to 70 μm or 10 μm to 50 μm.

[0050] In one embodiment of the present invention, when the all-solid-state battery is discharged after multiple charge-discharge cycles, the content of lithium remaining in the negative electrode active material layer may be 0.1 mol or more based on 1 mol of silicon. If the content of lithium remaining in the negative electrode active material layer is less than 0.1 mol, there is a problem that the life performance is significantly reduced when multiple charge-discharge cycles are performed.

[0051] In addition, the content of lithium remaining in the negative electrode active material layer is 2 wt % or more based on the total weight of the negative electrode. If the content of lithium remaining in the negative electrode active material layer is less than 2 wt %, there is a problem that the life performance is significantly reduced when multiple charge / discharge cycles are performed.

[0052] In one embodiment of the present invention, the negative electrode active material layer can be produced, for example, by the following method.

[0053] In one embodiment of the present invention, the negative electrode active material layer is formed by mixing silicon powder and lithium powder and applying pressure to the mixture. Alternatively, prelithiation can be carried out by placing lithium metal on the silicon negative electrode and applying a certain amount of pressure from above and below to bring the silicon negative electrode and lithium metal into direct contact. Direct contact between the silicon negative electrode and lithium metal allows lithium to react with the silicon active material to form an alloy, similar to the initial irreversibility. This reaction reduces the occurrence of irreversibility during subsequent charging, thereby making it possible to control the degree of initial irreversibility of the electrode. The pressure application method is not limited to a specific method, and any known pressure application method can be selected and applied.

[0054] In one embodiment of the present invention, the solid electrolyte may include a sulfide-based solid electrolyte, which contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and may include an argyrodite-based sulfide-based solid electrolyte.

[0055] In the present invention, the average particle size of the sulfide-based solid electrolyte can be adjusted to a range suitable for all-solid-state batteries. In a specific embodiment of the present invention, the solid electrolyte may have an average particle diameter of 0.1 μm to 50 μm. In another embodiment of the present invention, the selected solid electrolyte may have a particle size of 1×10 -5 S / cm, preferably 1×10 -3 It has an ionic conductivity of S / cm or more.

[0056] In one embodiment of the present invention, the solid electrolyte layer can be produced, for example, by the following method.

[0057] First, a solid electrolyte is prepared. The solid electrolyte can be obtained as a commercially available product or prepared by the following method. The solid electrolyte can be prepared by the following method.

[0058] First, LiCl, Li2S, and P2S5 are mixed in stoichiometric amounts and milled using a planetary ball mill or other method to obtain a homogeneous mixture. The mixture is then heat-treated at a high temperature for a predetermined period of time to obtain the desired Li6PS5Cl solid electrolyte. The heat treatment can be performed at approximately 550°C for approximately 8 hours.

[0059] Next, the solid electrolyte material is introduced into a predetermined organic solvent and dispersed to prepare a slurry, which is then applied to a release plate or the like, dried, and formed into a sheet. If necessary, the resulting sheet can be compressed to obtain a solid electrolyte layer.

[0060] In one embodiment of the present invention, the all-solid-state battery may include an interface layer between the solid electrolyte and the negative electrode active material layer, and the interface layer may be formed between the sulfide-based solid electrolyte and the prelithiated silicon negative electrode.

[0061] The interface layer may be made of one or more selected from Li2S, LiX (X: Cl, Br or I), or Li3P.

[0062] After charging the all-solid-state battery, the content of Li2S, LiX (X: Cl, Br, or I), or Li3P in the interface layer may be 1 to 50 mol% based on 100 mol% of the total content of the solid electrolyte and the interface layer. Specifically, after charging the all-solid-state battery, the content of Li2S, LiX (X: Cl, Br, or I), or Li3P in the interface layer may be 1 mol% or more, 5 mol% or more, 10 mol% or more, 15 mol% or more, or 20 mol% or more, or 50 mol% or less, 45 mol% or less, or 40 mol% or less, based on 100 mol% of the total content of the solid electrolyte and the interface layer. If the content of Li2S, LiX (X: Cl, Br, or I) or Li3P in the interface layer exceeds 50 mol% based on 100 mol% of the total content of the solid electrolyte and the interface layer, problems arise such as increased battery resistance and reduced battery capacity and rate characteristics.

[0063] In one embodiment of the present invention, the positive electrode may include a positive electrode active material layer containing a positive electrode active material, a positive electrode conductive material, and a solid electrolyte. The positive electrode active material layer may further include a binder resin for the positive electrode, if necessary. Further, the positive electrode may include a current collector, if necessary, and the positive electrode active material layer may be disposed on at least one surface of the current collector.

[0064] In one embodiment of the present invention, the positive electrode active material may include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33. For example, LiMn2O4), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2, lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV2O4, V2O5, Cu2V2O7, chemical formula LiNi 1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and 0 < x < 1), Ni-site type lithium nickel oxide represented by, for example, LiNi 1-z (Co, Mn, Al) z O2 (0 < z < 1); chemical formula LiMn 2-x M x O4 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 1. For example, LiMn 1.5 Ni 0.5 O4) or lithium manganese composite oxide represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compound; one or a mixture of two or more of Fe2(MoO4)3 and lithium iron phosphate (LiFePO4). In one embodiment of the present invention, the lithium iron phosphate may have all or at least a part of the surface of the active material particles coated with a carbon material for improving conductivity.

[0065] Preferably, the positive electrode active material is Lithium Nickel Cobalt Manganese Oxide (for example, Li(Ni, Co, Mn)O2, LiNi 1-z (Co, Mn, Al) z O2(0 < z < 1)), Lithium Iron Phosphate (for example, LiFePO4 / C), Lithium Nickel Manganese Spinel (for example, LiNi 0.5 Mn 1.5 O4), Lithium Nickel Cobalt Aluminium Oxide (for example, Li(Ni, Co, Al)O2), Lithium Manganese Oxide (for example, LiMn2O4), and Lithium Cobalt Oxide (for example, LiCoO2), and may contain one or more selected therefrom.

[0066] In the present invention, most preferably, the positive electrode active material contains a lithium transition metal composite oxide, and the transition metal may contain one or more of Co, Mn, Ni, and Al.

[0067] In one embodiment of the present invention, the lithium transition metal composite oxide may contain at least one or more of the compounds represented by the following Chemical Formula 1.

[0068] [Chemical Formula 1] Li x Ni a Co b Mn c M z O y In Chemical Formula 1, 0.5 ≦ x ≦ 1.5, 0 ≦ a ≦ 1, 0 ≦ b < 1, 0 ≦ c < 1, 0 ≦ z < 1, 1.5 < y < 5, a + b + c + z is 1 or less, and M contains one or more selected from Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge, and Sn.

[0069] In one specific embodiment of the present invention, the positive electrode conductive material may be, for example, any one selected from the group consisting of graphite, carbon black, carbon or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials thereof. More specifically, the positive electrode conductive material may be any one selected from the group consisting of natural graphite, artificial graphite, Super-P, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials thereof.

[0070] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, stainless steel, copper, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like can be used.

[0071] The positive electrode binder resin may be a polymer commonly used in electrodes in the art. Non-limiting examples of such binder resins include polyvinylidene difluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples of suitable polymers include, but are not limited to, cyanoethyl acetatepropionate, cyanoethyl pullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0072] In one embodiment of the present invention, the solid electrolyte contained in the positive electrode may include one or more selected from a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. In one embodiment of the present invention, the positive electrode active material may preferably include a sulfide-based solid electrolyte described above for the solid electrolyte.

[0073] In one embodiment of the present invention, the positive electrode active material is preferably contained in an amount of 70 wt % or more relative to 100 wt % of the positive electrode active material layer, and the solid electrolyte is preferably contained in an amount of 10 wt % to 30 wt % relative to 100 wt % of the positive electrode active material layer.

[0074] Meanwhile, in a specific embodiment of the present invention, the positive electrode has a capacity of 5 mAh / cm 2 More than 6mAh / cm 2 or more than 10mAh / cm 2 The loading amount (per electrode area) may be greater than or equal to 1000 ppm.

[0075] Even when such a high loading positive electrode is applied to the battery according to the present invention, the battery can be operated at an electrochemically stable level.

[0076] In one specific embodiment of the present invention, the positive electrode active material layer may be obtained by casting a slurry prepared by adding a positive electrode active material, a conductive material, a binder resin, and a solid electrolyte to an appropriate solvent, or by a dry mixing process without using a solvent. In another embodiment of the present invention, the positive electrode is preferably obtained by a dry mixing process without using a solvent, from the viewpoint of achieving homogeneous mixing of the positive electrode components in the positive electrode and thereby obtaining a high-loading positive electrode.

[0077] The method for manufacturing a cathode active material layer using the dry mixing method can be described as follows. First, cathode materials including a cathode active material, a conductive material, and a binder resin are loaded into a mixer and mechanically mixed to obtain a mixture. The mixer may be any device capable of obtaining a relatively uniform mixture, such as a known mixer or agitator, and is not limited to any particular device. Meanwhile, in one embodiment of the present invention, a heating process may be included to improve the dispersibility of the solids in the mixing process and induce the formation of a fibrous phase in the binder resin. The temperature during the heating process may be appropriately controlled within a range of about 30°C to 100°C. Next, the mixture is extruded into a cathode active material layer in the form of an electrode (wide film), and the thickness may be adjusted by a pressure process. The cathode active material layer may be applied to an electrode without a current collector, or, if necessary, a current collector may be attached to the obtained cathode active material layer to prepare a cathode including the current collector.

[0078] The present invention will be described in more detail below through examples, but the following examples are provided to illustrate the present invention and are not intended to limit the scope of the present invention. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0079] [Example 1] (1) Manufacturing of the negative electrode Silicon (Si) powder (Alfa Aesar, particle size 3 μm to 5 μm) and lithium (Li) powder (FMC Corp.) were added in the appropriate molar ratio, mixed using a vortex mixer, and then pressed between two titanium rods at 200 MPa to prepare a prelithiated silicon anode.

[0080] The molar ratio of the silicon powder to the lithium powder was 1:0.25.

[0081] The thickness of the prepared negative electrode was 45 μm, and the loading capacity of the negative electrode was 13.2 mAh / cm 2 It was.

[0082] (2) Manufacturing of the positive electrode LCO (MTI, LiCoO2), Li6PS5Cl (NEI Corporation), and VGCF (Sigma Aldrich (Graphitized, Iron-free)) were mixed in a weight ratio of 66:31:3, dry-mixed in a heated mortar, and then pressed between two titanium rods at 370 MPa to prepare a positive electrode.

[0083] The thickness of the prepared positive electrode was 70 μm, and the loading capacity of the positive electrode was 3.0 mAh / cm 2 It was.

[0084] (3) Manufacturing of solid electrolyte layer 75 mg of Li6PS5Cl (NEI Corporation) was pressed between two titanium rods at 370 MPa to produce a 700 μm thick solid electrolyte layer.

[0085] (4) Battery manufacturing The negative electrode, positive electrode, and solid electrolyte layer prepared as above were pressurized at a pressure of 370 MPa using a titanium plunger, which was used as a current collector, to fabricate a battery.

[0086] [Example 2] A battery was manufactured in the same manner as in Example 1, except that the molar ratio of the silicon powder to the lithium powder was 1:1.

[0087] [Example 3] A battery was manufactured in the same manner as in Example 1, except that the molar ratio of the silicon powder to the lithium powder was 1:2.

[0088] [Comparative Example 1] Silicon powder (Alfa Aesar, particle size 3 μm to 5 μm) was pressed between two titanium rods at 200 MPa to fabricate a silicon negative electrode.

[0089] The positive electrode and the solid electrolyte layer were prepared in the same manner as in Example 1. The negative electrode, the positive electrode, and the solid electrolyte layer were pressurized at a pressure of 370 MPa using a titanium plunger to manufacture a battery. The titanium plunger was used as a current collector.

[0090] Comparative Example 2 A battery was manufactured in the same manner as in Example 1, except that the molar ratio of the silicon powder to the lithium powder was 1:3.

[0091] [Experimental Example] Experimental Example 1: Battery life characteristics The life characteristics of the batteries of Examples 1 to 3 and the battery of Comparative Example 1 were compared and are shown in Figure 4. Figure 4 shows the life characteristics at room temperature (25°C), and it was confirmed that the capacity retention rate of Example 3, which had a high lithium content in the prelithiated silicon negative electrode, was the highest.

[0092] Experimental Example 2: Evaluation of the electrochemical performance of the battery The capacity retention rate and coulombic efficiency after 1000 charge-discharge cycles were compared for the batteries of Examples 1 to 3 and the battery of Comparative Example 1, and the results are shown in Figure 5. 2 After 1000 charge / discharge cycles, the capacity retention rate and coulombic efficiency were confirmed. It was confirmed that the battery of Comparative Example 1 exhibited a capacity retention rate of approximately 20% and an average coulombic efficiency of 58.7%, while the battery of Example 3 exhibited a capacity retention rate of 80% and an average coulombic efficiency of 99.9%.

[0093] Experimental Example 3: X-ray photoelectron spectroscopy measurement of the interface between the solid electrolyte layer and the negative electrode active material layer The formation of Li2S in the interface layer between the solid electrolyte and the prelithiated negative electrode active material layer was confirmed before and after charging the battery. Table 1 below shows X-ray photoelectron spectroscopy (XPS) measurement data for the solid electrolyte layer and interface layer of Example 2 and Comparative Example 2.

[0094] [Table 1]

[0095] As shown in Table 1, Example 2 showed that an appropriate amount of Li2S was formed at the interface between the silicon anode and the solid electrolyte layer, suppressing further reductive decomposition of the electrolyte and improving battery efficiency. On the other hand, Comparative Example 2 showed that excessive Li2S was formed at the interface layer after charging the battery, which increased resistance and reduced battery performance.

[0096] Experimental Example 4: Measurement of the remaining lithium in the negative electrode after charge-discharge cycles The batteries prepared in Examples 1 to 3 and Comparative Example 1 were charged and discharged 10 times, and then overdischarged to 0 V to measure the amount of lithium remaining in the negative electrode. The results are shown in Table 2 below.

[0097] [Table 2]

[0098] As shown in Table 2, the batteries including the prelithiated negative electrodes prepared in Examples 1 to 3 were confirmed to have residual lithium remaining in the negative electrodes even after multiple charge / discharge cycles. The content of lithium remaining in the negative electrodes according to Examples 1 to 3 was 0.1 mol or more based on 1 mol of silicon, or 2 wt% or more based on the total weight of the negative electrodes. On the other hand, the content of lithium remaining in the negative electrode according to Comparative Example 1 after multiple charge / discharge cycles was very low, at 0.02 mol based on 1 mol of silicon, or 0.5 wt% based on the total weight of the negative electrodes. It was found that a low content of lithium remaining in the negative electrodes after the charge / discharge cycles leads to a decrease in battery performance.

[0099] Experimental Example 5: Battery efficiency depending on the ratio of Li and Si FIG. 1 shows the initial conductivity of the negative electrodes according to Examples 1 to 3 and Comparative Examples 1 and 2. It was confirmed that the initial conductivity of the negative electrodes according to Examples 1 to 3 increases with increasing lithium ratio per mole of silicon in the prelithiated silicon negative electrode. On the other hand, the silicon negative electrode according to Comparative Example 1 had an initial conductivity of 2.5×10 -4 The initial efficiency was significantly lower than that of the pre-lithiated silicon anode, at 1000 s / cm. Furthermore, in Comparative Example 2, the initial efficiency was not measured when the lithium ratio per 1 mole of silicon exceeded 3 in the pre-lithiated silicon anode. This indicates that the battery efficiency rapidly decreased when the anode contained 3 moles or more of lithium per mole of silicon.

Claims

1. An all-solid-state battery including a negative electrode, a positive electrode, and a sulfide-based solid electrolyte interposed between the negative electrode and the positive electrode, the negative electrode includes a negative electrode active material layer containing silicon (Si), the negative electrode is prelithiated; an interface layer between the solid electrolyte and the negative electrode active material layer.

2. The sulfide-based solid electrolyte is an argyrodite-based sulfide-based solid electrolyte (Li ６ P.S. ５ X; X = Cl, Br, I). The all-solid-state battery according to claim 1 .

3. The interface layer is Li ２ S, LiX (X: Cl, Br or I) or Li ３ The all-solid-state battery according to claim 1 , wherein the all-solid-state battery comprises one or more selected from P.

4. 2. The all-solid-state battery according to claim 1, wherein the negative electrode active material layer contains 0.25 mol to 2 mol of lithium per 1 mol of silicon.

5. After charging the all-solid-state battery, Li in the interface layer ２ S, LiX (X: Cl, Br or I) or Li ３ 4. The all-solid-state battery according to claim 3, wherein the content of P is 1 to 50 mol % based on 100 mol % of the total content of the solid electrolyte and the interface layer.

6. The silicon is composed of a plurality of silicon particles, 2. The all-solid-state battery according to claim 1, wherein the silicon particles have a particle size of 0.1 μm to 10 μm.

7. In a discharged state after multiple charge / discharge cycles of the all-solid-state battery, The all-solid-state battery of claim 1 , wherein the content of lithium remaining in the negative electrode active material layer is 0.1 mol or more based on 1 mol of silicon.

8. The all-solid-state battery according to claim 1 , wherein the negative electrode active material layer further contains a conductive material.

9. the positive electrode includes a positive electrode active material layer, the positive electrode active material layer contains a lithium transition metal composite oxide, The all-solid-state battery according to claim 1 , wherein the transition metal comprises one or more of Co, Mn, Ni, and Al.

10. The all-solid-state battery according to claim 9, wherein the lithium transition metal composite oxide comprises at least one compound represented by the following Chemical Formula 1: [Chemical formula 1] Li ｘ Ni ａ Co ｂ Mn ｃ M ｚ O ｙ In Chemical Formula 1, 0.5≦x≦1.5, 0≦a≦1, 0≦b<1, 0≦c<1, 0≦z<1, 1.5<y<5, a+b+c+z is 1 or less, and M includes at least one selected from Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge, and Sn.

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