Negative electrode - glass electrolyte laminate, all-solid-state secondary battery including the same, and method for manufacturing the same

Abstract

The exemplary embodiment includes a negative electrode and a glass electrolyte layer on at least one surface of the negative electrode, and the negative electrode includes a surface-passivated lithium-containing metal foil, and the laminate relates to a negative electrode-glass electrolyte layer laminate that is electrochemically operable without external pressure, an all-solid-state secondary battery including the negative electrode-glass electrolyte layer laminate, and a method for manufacturing the negative electrode-glass electrolyte layer laminate.

Description

Technical Field

[0001] This invention was made with government support under Award No. DE-AR0000772, awarded by the Advanced Research Projects Agency-Energy (ARPA-E) of the U.S. Department of Energy. The government has certain rights in this invention.

[0002] The present invention relates to a negative electrode-glass electrolyte laminate, an all-solid-state secondary battery including the same, and a method for manufacturing the same.

Background Art

[0003] An all-solid-state secondary battery generally includes a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched therebetween. The solid electrolyte layer contains a solid electrolyte, and the positive electrode and the negative electrode each contain an active material and generally a solid electrolyte.

[0004] Compared with a battery including a liquid electrolyte, an all-solid-state secondary battery has a lower risk of explosion or fire and is attracting attention as a next-generation secondary battery due to its potential for high energy density.

[0005] In particular, as the active material of the negative electrode, a solid battery based on lithium metal is promising. Lithium metal is preferable in batteries due to its high theoretical capacity (3.86 Ah / g), low density, and electropositivity (-3.04 V vs. SHE). Lithium metal primary batteries are characteristically well-known for their high cell voltage (>3 volts), miniaturization, and weight reduction. Also, it is well-known that lithium metal foil is surface passivated because when the foil is formed in an oxygen-deficient environment, metallic lithium spontaneously reacts with oxygen to form a native oxide surface film. The native film is advantageous in that it provides the surface passivation necessary against the degradation of oxidation performance during storage and subsequent processing. However, the presence of the native oxide film can, in certain cases, have a negative impact on cell performance and generally poses an obstacle to layer adhesion (for example, when attempting to bond or laminate a lithium metal foil and a solid electrolyte layer). SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] Accordingly, the present disclosure relates to layer adhesion issues associated with directly laminating a lithium metal foil to a solid electrolyte layer. MEANS FOR SOLVING THE PROBLEMS

[0007] In one aspect, the present disclosure provides a negative electrode composed of a surface passivated lithium-containing metal foil laminated (HHT-laminated) to a sulfide glass electrolyte layer at a high homologous temperature, and this negative electrode has excellent adhesiveness between the glass electrolyte layer and the lithium-containing metal foil. According to the present disclosure, the lamination is performed at a sufficiently high homologous temperature of the metal foil in such a manner that all native films (for example, oxides, carbonates, or combinations thereof) on the foil surface are absorbed by what is called a "lamination layer" that is reactively formed at the interface and is absorbed.

[0008] The laminated layer shall not provide excessive interfacial resistance. Specifically, the laminate thus formed has a low interfacial resistance even without applying pressure. By using the term surface passivation, it means having an oxidized or carbonated surface (i.e., a native oxide and / or carbonate film) that is substantially protected from further reactions when the pre-laminated lithium-containing metal foil is stored or handled in an oxygen-deficient environment. According to the present disclosure, the native film is absorbed by the laminated layer formed at the interface between the lithium-containing metal foil and the glass electrolyte layer as a result of the lamination being performed at a sufficiently high homologous temperature of at least 0.85, particularly below the crystallization temperature of the glass electrolyte layer.

[0009] When using the term "homologous temperature", this refers to the temperature of the lithium-containing active material of the negative electrode, and is useful in the present application because the temperature of the material is expressed as a fraction of the melting point temperature using the Kelvin scale. Thus, this makes it possible to compare the working conditions of various lithium-containing metal foils and is related to the deformation due to diffusion that may occur when laminating at a high temperature (e.g., near the melting point of the metal foil). Therefore, the terms "HHT-lamination" or "HHT-laminate" are sometimes used in the present application and the claims when referring to a laminate formed at a homologous temperature of at least 0.85 and less than 1.

[0010] Yet another aspect of the present disclosure is that the glass electrolyte film and the lithium-containing metal foil are about 0.05 to 0.3 kgf / cm 2A method for manufacturing a negative electrode - glass electrolyte layer laminate laminated at a homologous temperature between 0.85 and <1 (for example, in the case of a lithium metal foil, in the range of 120 to 180 °C) under a specific pressure within a range can be provided. In various embodiments, the lamination step is performed in an inert non - vacuum environment such as a chamber filled with argon or a drying oven. In a specific embodiment, the native film on the lithium metal foil surface is sufficiently strong, and the lamination temperature is high enough to be able to perform the lamination step in a dry indoor environment of ambient air with a low moisture content (for example, dew point - 40 °C or lower). In various embodiments, the native oxide film is controllably formed before lamination. For example, a lithium - containing metal foil in the received or formed state is pretreated by abrading the surface before lamination, exposing fresh lithium metal to a gas - oxygen - containing environment, and forming a controlled native oxide film, which generally has a thickness of 100 nm to 1 μm.

[0011] In various embodiments, this method includes melting and wetting lithium metal to form a lithium metal layer, and before completely cooling the lithium metal layer, lightly pressing and placing a solid electrolyte on the lithium metal surface and laminating it to a glass electrolyte film at a sufficiently high homologous temperature (for example, 0.85 to <1).

[0012] According to an aspect of the present disclosure, a negative electrode - glass electrolyte layer laminate can include a negative electrode and a glass electrolyte layer on at least one surface of the negative electrode, where the negative electrode includes a lithium - containing metal foil having a native film that is sufficiently absorbed by the lamination layer or extruded again at the depth of the Li foil, so that when the pressure applied to the negative electrode - glass electrolyte layer laminate is 0 kgf / cm 2 it operates so that the laminate can be used in a battery cell.

[0013] The negative electrode - glass electrolyte layer laminate can satisfy the following formula (1):

[0014] [|(R1 - R2)| / R]×100≦10% (1)

[0015] Here, R2 is the interfacial resistance between the negative electrode and the glass electrolyte layer when the pressure applied to the negative electrode-glass electrolyte layer laminate is 0.3 kgf / cm 2 is the interfacial resistance between the negative electrode and the glass electrolyte layer when the pressure applied to the negative electrode-glass electrolyte layer laminate is 0.3 kgf / cm

[0016] Specifically, the lamination step is performed at a homologous temperature and pressure that are high enough such that deformation by diffusion realizes a negative electrode-glass electrolyte layer laminate having no pores at the interface between the negative electrode and the glass electrolyte layer.

[0017] In the present application, the interface between the negative electrode and the glass electrolyte layer can include what is referred to as a "laminated layer formed by the reaction of a lithium-containing metal and a sulfide-based glass electrolyte."

[0018] The thickness of the laminated layer is not particularly limited. It may be in the range of greater than about 0 μm to about 30 μm or less. For example, greater than 0 μm, 0.001 μm or more, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 1 μm or more, 3 μm or more, or 5 μm or more, and 30 μm or less, for example, 25 μm or less, 20 μm or less, 17 μm or less, or 15 μm or less. For example, the laminated layer can have a thickness of about 20 μm.

[0019] The glass electrolyte layer may be a monolithic electrolyte layer. The glass electrolyte layer can have a thickness of, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 50 μm or more, or 10 μm or more, and 1000 μm or less, for example, 800 μm or less, 700 μm or less, 500 μm or less, 300 μm or less, or 200 μm or less. For example, the glass electrolyte layer can have a thickness of about 200 μm, about 100 μm, about 50 μm, about 30 μm, about 20 μm, or about 10 μm.

[0020] The glass electrolyte layer is based on sulfide.

[0021] The glass electrolyte layer can contain Li, S, P, Si, As, and B.

[0022] In various embodiments, a method of manufacturing a negative electrode - glass electrolyte layer includes a hot lamination process that includes: providing a surface - passivated lithium - containing metal foil, laminating the foil onto a sulfide - based glass electrolyte film, and heating and applying pressure to laminate the lithium - containing metal foil and the sulfide - based glass electrolyte film at a homologous temperature of about 0.85 or more to <1.

[0023] Lamination can be performed at a temperature of 140 - 180°C.

[0024] Lamination can be performed at a pressure of 0.05 - 0.3 kgf / cm 2 of pressure.

[0025] Lamination can be performed for 5 - 30 minutes. In various embodiments, lamination is performed for 1 minute or less (e.g., about 60 seconds, about 50 seconds, about 40 seconds, about 30 seconds, about 20 seconds, about 10 seconds, or about 5 seconds).

[0026] In various embodiments, high - speed HHT lamination is used, and a high homologous temperature close to 1 (e.g., >0.9) is used for a time of about 5 seconds or less (e.g., about 5 seconds, about 4 seconds, about 3 seconds, about 2 seconds, about 1 second, or about 500 milliseconds). For example, it may be high - speed lamination at a homologous temperature of 5 - 1000 milliseconds to <1. The high homologous temperature in the high - speed lamination stage can minimize the lamination pressure. In various embodiments, the laminate is formed by high - speed lamination at a pressure in the range of about 0.01 - <1 kgf / cm 2 of pressure.

[0027] The lamination step is generally performed in an oxygen - deficient environment such as an inert non - vacuum environment (e.g., a chamber or drying oven filled with argon). However, the present disclosure is not limited thereto, and the lamination step is considered to be sufficiently robust to allow laminating the layers in an air environment such as a drying chamber with a sufficiently low moisture content.

[0028] In various embodiments, the received lithium metal foil or lithium-containing metal foil is processed by abrading the surface, removing the native film in a controllable manner, and reforming it. For example, after abrading the surface of lithium, it is exposed to a controlled atmospheric environment for a certain period of time. Specifically, the lamination step is carried out substantially immediately after the native film is formed. In various embodiments, the controlled atmosphere has a very low water content (e.g., <10 ppm H2O). In other embodiments, the atmosphere is a low-oxygen-containing environment such as a drying chamber filled with air having a dew point of < -40°C. According to still other aspects of the present disclosure, the all-solid-state secondary battery can include a negative electrode-glass electrolyte layer laminate and a positive electrode as described in the present application.

[0029] The all-solid-state secondary battery can further include a solid electrolyte layer between the glass electrolyte layer of the negative electrode-glass electrolyte layer laminate and the positive electrode.

Brief Description of the Drawings

[0030] The above and other aspects, features, and other advantages of the present disclosure can be more clearly understood from the following detailed description described together with the accompanying drawings.

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0032] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0033] In the present application, unless otherwise defined, all technical terms and scientific terms have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the present application are for effectively explaining specific examples and are not intended to limit the present invention.

[0034] In the present application, the singular forms are intended to include the plural forms as well, unless otherwise indicated in the context.

[0035] Also, the numerical ranges used in the present application include all values within the range including the lower limit and the upper limit, forms within the defined range, increments logically derived from the range, all double-limited values, and all possible combinations of the upper and lower limits in other forms of defined numerical ranges. Unless otherwise defined in this specification, values that may deviate from the numerical range due to experimental errors or rounding of values are also included in the defined numerical range.

[0036] The term "comprising" in the present application is an open-ended description having the same meaning as terms such as "provided", "containing", "having", or "characterized by", and does not exclude elements, substances, or steps not further listed.

[0037] In the present application, the term "A and / or B" can refer to an embodiment including both A and B, or an embodiment selecting one of A and B.

[0038] In this application, when an element such as a layer, film, region, or substrate is referred to as being "on" or "above" another element, it should be understood that it may be directly on top of the other element, or there may also be intervening elements.

[0039] An exemplary embodiment provides a negative electrode - glass electrolyte layer laminate in which a negative electrode and a glass electrolyte film are laminated, and an example of the negative electrode - glass electrolyte layer laminate is schematically shown in FIG. 1.

[0040] Referring to FIG. 1, the negative electrode - glass electrolyte layer laminate 20 (hereinafter also simply referred to as "laminate") can include a negative electrode 21 and a glass electrolyte layer 25 on at least one surface of the negative electrode 21. Specifically, the glass electrolyte layer 25 can be laminated on at least one surface of the negative electrode 21. The negative electrode 21 may be a lithium - containing metal negative electrode, and specifically, it can include a lithium - containing metal foil. The glass electrolyte layer 25 is based on sulfide, but alternative compositions containing oxides can be considered, for example, it can be based on sulfide.

[0041] Specifically, the glass electrolyte layer 25 can be laminated on one surface of the lithium - containing metal negative electrode. More specifically, the sulfide - based glass electrolyte layer can be laminated on one surface of the lithium - containing metal negative electrode.

[0042] As an example, the lithium - containing metal foil may be a foil consisting only of lithium metal, or it may be an alloy foil of lithium and other metals. For example, as long as it can be used as a negative electrode in a secondary battery containing a sulfide - based solid electrolyte, it is not limited. The metal forming an alloy with lithium may be a metal selected from Group 13, Group 14, and Group 15 elements of the periodic table, but is not limited thereto. Specifically, In, Al, Sn, Si, Mg, Zn, Ge, Ag, etc. can be mentioned. Any one of them can be alloyed with lithium, and two or more metals can be alloyed with lithium.

[0043] As an example, the negative electrode 21 may not contain a particulate negative electrode active material. More specifically, the negative electrode may not contain particulate negative electrode deposits, where the negative electrode deposits may include dendritic shapes. When the negative electrode contains a particulate negative electrode active material, pores are generated in the negative electrode or on the surface of the negative electrode by the particulate negative electrode active material, and point contacts are formed between the particulate negative electrode active material and the glass electrolyte layer. Therefore, a sufficient reaction active region is not ensured at the interface between the negative electrode and the glass electrolyte layer, and the interface resistance increases.

[0044] The glass electrolyte layer 25 is a monolithic electrolyte layer without pores inside. Since no interface resistance occurs inside the glass electrolyte layer 25, it provides excellent lithium ion conductivity.

[0045] The glass electrolyte layer 25 can be based on sulfides, and specific compositional components are not particularly limited as long as the electrolyte component contains sulfur atoms and can form an amorphous state. Also, the glass electrolyte may be a crystalline glass electrolyte (i.e., glass ceramic) or a completely amorphous glass electrolyte.

[0046] The sulfide-based electrolyte forming the glass electrolyte layer 25 can contain Li, S, P, Si, B, and As. Specifically, LPS-type sulfides containing sulfur and phosphorus, Li 4-x Ge 1-x P x S4 (where x is from 0.1 to 1, specifically, x is 3 / 4, 2 / 3), Li 10±1 MP2X 12 (M = Ge, Si, Sn, Al, X = S, Se), Li 3.833 Sn 0.833 As 0.166 S4, Li4SnS4, Li 3.25 Ge 0.25 P 0.75 S4, xLi2S-(100-x)P2S5 (where x is from 70 to 80) obtained by combining one or more of Li2S and P2S5, B2S3, SiS2, and GeS2, Li2S-SiS2-Li3N, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li2S-B2S3-LiI, etc. are included, but not limited thereto.

[0047] In FIG. 2, an example of a powder-compressed cell 10 in which a particulate solid electrolyte layer 15 containing a particulate solid electrolyte is formed on the surface of a lithium-containing metal negative electrode 11 is schematically shown.

[0048] Referring to FIG. 2, a plurality of pores 17 can be formed inside the particulate solid electrolyte layer 15, and the interface resistance within the particulate solid electrolyte layer 15 can be increased by the pores 17. Further, a point contact is formed at the interface between the lithium-containing metal negative electrode 21 and the particulate solid electrolyte layer 15, increasing the interface resistance, and since the adhesion strength between the lithium-containing metal negative electrode 11 and the particulate solid electrolyte layer 15 cannot be sufficiently obtained, there is a possibility of delamination occurring.

[0049] Therefore, in order to solve the problems of high interface resistance and delamination occurring at the interface between the inside of the particulate solid electrolyte layer 15 and the lithium-containing metal negative electrode 11 and the particulate solid electrolyte layer 15, it is necessary to continuously pressurize the battery of the powder-compressed cell 10 of the lithium-containing metal negative electrode and the particulate solid electrolyte layer to maintain interface contact during battery operation.

[0050] For example, a conventional all-solid-state secondary battery including a particulate solid electrolyte layer 15 requires means to apply or maintain a compressive stress of 5 tons / cm 2 or more in order to minimize the resistance of the electrochemical reaction occurring at the interface between the electrode and the electrolyte layer during electrode manufacturing, battery manufacturing, or battery operation.

[0051] However, in the laminate 20 according to an exemplary embodiment, the contact property between the negative electrode 21, specifically, the negative electrode 21 including a lithium-containing metal foil and the glass electrolyte layer 25 is improved, reducing the interface resistance, and the battery can be driven without separate crimping. Therefore, in an electric vehicle or the like, no additional crimping means for battery driving are required, and since a crimping restraint device is unnecessary, the weight can be reduced, the loading efficiency can be increased, and the space utilization ability can be enhanced.

[0052] More specifically, the laminate 20 is integrated by laminating the glass electrolyte layer 25 on the negative electrode of the lithium-containing metal foil, and has excellent adhesive force at the interface, and the problem of delamination between layers can be reduced. Integration means that two layers can be laminated at the interface between the negative electrode of the lithium-containing metal foil and the glass electrolyte layer 25 without a separate binder.

[0053] Hereinafter, a method for manufacturing the laminate 20 according to an exemplary embodiment will be described.

[0054] Normally, when laminating a lithium-containing metal foil and a sulfide-based solid electrolyte (amorphous or crystalline) without heat, the resulting laminate has insufficient adhesive force, and a uniform insertion and desorption process of lithium ions does not occur during the charging and discharging processes, so dendrites may be formed. Furthermore, the lithium-containing metal foil and the glass electrolyte film are likely to peel off. Therefore, in order to maintain the interfacial contact between the lithium-containing metal foil and the glass electrolyte film, a means for continuously providing pressure to the battery may be required.

[0055] The negative electrode-glass electrolyte layer laminate according to an exemplary embodiment can be manufactured by the following method. FIG. 3 schematically shows the concept of manufacturing the laminate according to an exemplary embodiment.

[0056] Referring to FIG. 3, in the negative electrode-glass electrolyte layer laminate 20 according to an exemplary embodiment, laminating the lithium-containing metal foil and the glass electrolyte film 31 on the lithium-containing metal foil 35 is included. The lithium-containing metal foil 35 and the glass electrolyte film 31 are as described above for the negative electrode 21 and the glass electrolyte layer 25 of the laminate 20, respectively, and the shapes of the lithium-containing metal foil 35 and the glass electrolyte film 31 are not particularly limited, and a shape formed into the shape of the provided electrode can be used.

[0057] Next, manufacturing the laminate 20 in which the lithium-containing metal foil 35 and the glass electrolyte film 31 are laminated is included.

[0058] The lamination can be performed using a heating plate including an upper plate 41 and a lower plate 43 as shown in FIG. 3. The heating plate can heat the upper plate 41 and the lower plate 43 to a predetermined high isothermal temperature and perform pressure bonding, and can directly laminate the lithium-containing metal foil 35 on the glass electrolyte film 31.

[0059] Specifically, in various embodiments, the lithium-containing metal foil 35 and the glass electrolyte film 31 are heated and pressure-bonded both on the upper and lower sides, and the heating and pressure-bonding are distinguished from heating the upper plate 41 or the lower plate 43 of the heating plate on the side surface of the lithium-containing metal foil 35 to form the lithium metal into a predetermined shape and then performing pressure bonding.

[0060] The heating plate is not particularly limited as long as it can heat both the upper plate 41 and the lower plate 43, and can be appropriately used as long as it includes heating means for heating both the upper plate 41 and the lower plate 43 of the heating plate.

[0061] Also, the pressure bonding may be performed by moving either one of the upper plate 41 and the lower plate 43 to apply pressure, or by moving the upper plate 41 and the lower plate 43 so as to face each other for pressure bonding.

[0062] The heating for lamination is performed at a high isothermal temperature in the range of 0.85 to <1. For example, in the case of a lithium metal foil, the heating for lamination can be performed at a temperature of 120° C. or higher, specifically 130° C. or higher, more specifically 140° C. or higher, and can be performed at a temperature of 180° C. or lower, specifically 170° C. or lower, more specifically 165° C. or lower. If the heating temperature is less than 120° C. (or an isothermal temperature less than 0.85), the lithium-containing metal foil 35 may not soften, making it difficult to laminate the foil and the glass electrolyte film 31. If the heating temperature exceeds 180° C. (i.e., an isothermal temperature of 1 or more), the lithium-containing metal foil 35 may melt and flow, and furthermore, the glass electrolyte film 31 may crystallize and the conductivity of lithium ions may decrease.

[0063] The pressure applied for lamination is not particularly limited, but it is 0.01 kgf / cm 2 or more, specifically 0.3 kgf / cm 2 or more, more specifically 0.05 kgf / cm 2 or more and 3 kgf / cm 2 or less, specifically 1 kgf / cm 2 or less, more specifically 0.5 kgf / cm 2 or less, even more specifically 0.3 kgf / cm 2 or less may be sufficient. If the applied pressure is less than 0.01 kgf / cm 2 , there may be no interfacial contact. If the pressure exceeds 3 kgf / cm 2 , cracks may occur in the glass electrolyte film.

[0064] The lamination time by heating and pressurization can be adjusted according to the thicknesses of the lithium-containing metal foil 35 and the glass electrolyte film 31, and is not particularly limited, but may be 5 to 30 minutes. If the lamination time is less than 5 minutes, sufficient interfacial lamination may not occur between the lithium-containing metal foil 35 and the glass electrolyte film 31. If the lamination time exceeds 30 minutes, the lithium-containing metal foil 35 may melt.

[0065] Since the glass electrolyte film 31 has low wettability with respect to the lithium-containing metal foil 35, when the lithium-containing metal foil 35 melts, the lithium-containing metal foil 35 may not be laminated on the interface with the glass electrolyte film 31 while maintaining a plate shape, and the lithium-containing metal foil 35 may bend and curl.

[0066] As an example, the glass electrolyte film 31 and the lithium-containing metal foil 35 are heated and pressurized vertically to soften the lithium-containing metal foil 35, and a laminated layer is formed at the interface between the lithium-containing metal foil 35 and the glass electrolyte film 31. The lithium-containing metal foil 35 and the glass electrolyte film 31 are integrated by the laminated layer to form a negative electrode-glass electrolyte layer laminate 20 in which the two layers are firmly laminated.

[0067] In the negative electrode - glass electrolyte laminate 20 according to an exemplary embodiment, the thicknesses of the negative electrode 21 and the glass electrolyte layer 25 are not particularly limited. For example, the negative electrode 21 can have a thickness of 1 μm or more, for example, 3 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, or 50 μm or more, and 1000 μm or less, for example, 700 μm or less, 500 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, or 100 μm or less. Further, the glass electrolyte layer 25 can have a thickness of 1 μm or more, for example, 3 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 50 μm or more, or 100 μm or more, and 1000 μm or less, for example, 800 μm or less, 700 μm or less, 500 μm or less, 300 μm or less, or 200 μm or less.

[0068] In various embodiments, the lithium - containing metal foil is a lithium metal foil. For example, this can be extruded from a lithium ingot as a free - standing lithium metal foil, extruded together with a current - collecting foil that is generally a copper foil (for example, in the range of about 5 μm to 15 μm in thickness), or a lithium foil that is contacted later.

[0069] In various embodiments, the laminate is formed by flash lamination at a high degree of congruent temperature in the range of 0.9 to <1 (for example, close to 1 but less than 1).

[0070] The cross - section of the negative electrode - glass electrolyte layer laminate 20 according to an exemplary embodiment is shown in FIG. 4. FIG. 4 is an SEM photograph of the cross - section of the laminate 20 according to Example 1 described later, taken at magnifications of 400 times (a), 1,000 times (b), and 2,000 times (c), respectively.

[0071] Referring to each SEM photograph of FIG. 4, the laminate 20 includes a negative electrode of lithium-containing metal 21 and a glass electrolyte layer 25, and a laminated layer 23 in which lithium metal and the glass electrolyte are mixed by softening of the lithium metal is included at the interface between the negative electrode 21 and the glass electrolyte layer 25, and the negative electrode 21 and the glass electrolyte layer 25 can be laminated by the laminated layer 23. Therefore, the laminated layer is composed of one or more (e.g., oxygen) of the elemental components of the sulfide glass electrolyte, particularly sulfur, lithium, and other elements of the native film on the lithium surface in general, oxygen and carbon.

[0072] Specifically, the laminated layer 23, the negative electrode 21, and the glass electrolyte layer 25 may have no pores.

[0073] The thickness of the laminated layer 23 is not particularly limited, but may be, for example, 0.1 μm or more, for example, 0.3 μm or more, 0.5 μm or more, 1 μm or more, 3 μm or more, or 5 μm or more, and 30 μm or less, for example, 25 μm or less, 20 μm or less, 17 μm or less, or 15 μm or less.

[0074] As an example, since there are no particles in the negative electrode 21 and the glass electrolyte layer 25 of the laminate 20, there are no pores in the negative electrode 21 and the glass electrolyte layer 25, and since there are no pores in the interface and the laminated layer 23 while the two layers are laminated by the laminated layer 23, the interface resistance between the two layers can be maintained at a low value, and the laminated layer can be electrochemically operated.

[0075] Also, when not pressed against the laminate 20 according to this exemplary embodiment (0 kgf / cm 2 ), the change rate of the interface resistance R1 and the interface resistance R2 between the negative electrode 21 and the glass electrolyte layer 25 when a pressure of 0.3 kgf / cm 2 is applied can satisfy the following formula (1):

[0076] [|(R1 - R2)| / R1]×100 ≦ 10% (1)

[0077] Thus, since the laminate 20 has excellent adhesion between the negative electrode 21 and the glass electrolyte layer 25, the interfacial resistance is low, and the change in the interfacial resistance before and after crimping may be small. Specifically, the peel strength of the laminate is greater than the tensile strength of the lithium metal. Therefore, when the laminate 20 is used, the battery can be continuously driven even when no means for maintaining a separate pressure is provided during battery evaluation and battery operation.

[0078] Also, in an exemplary embodiment, a positive electrode is laminated on the laminate 20 in which the negative electrode 21 and the glass electrolyte layer 25 are laminated to manufacture an all-solid-state secondary battery, specifically, an all-solid-state secondary battery including a sulfide-based solid electrolyte. The positive electrode can be disposed on the glass electrolyte layer 25 of the laminate 20. Further, if necessary, a solid electrolyte layer may be further included between the positive electrode and the laminate 20. At this time, the solid electrolyte layer may be based on an oxide or a sulfide, but is not limited thereto.

Example

[0079] Hereinafter, the present invention will be specifically described by way of examples. The following examples are for specifically explaining the present invention, and the present invention is not limited thereto.

[0080] Example 1 A lithium metal foil with a thickness of 200 μm was die-cut into a circle with a diameter of 6 mm.

[0081] Two circular lithium ion conductive sulfide-based glass electrolyte disks with a thickness of 500 μm and a diameter of 10 mm were prepared.

[0082] In a main glove box filled with argon gas, a lithium metal foil was positioned above and below the sulfide-based glass electrolyte film, and circular copper foil current collectors with a thickness of 15 μm and a diameter of 6 mm were positioned on both sides. Then, this was positioned between a pair of heating plates (SUS), and heated and crimped at a homologous temperature of 1 directly below (about 175°C) and a pressure of 0.2 kgf / cm 2 for 30 minutes to manufacture a symmetric cell in which the sulfide-based glass electrolyte layer was laminated above and below the lithium metal negative electrode.

[0083] In the symmetric cell manufactured in this way, the cross-sections of the lithium metal negative electrode and the sulfide-based glass electrolyte layer were photographed by SEM, and the results are shown in FIG. 4. In FIG. 4, (a), (b), and (c) are SEM photographs taken at magnifications of 400 times, 1,000 times, and 2,000 times, respectively.

[0084] As can be seen from each of the SEM photographs in FIG. 4, in the laminate obtained in Example 1, it was found that the lithium metal softened between the lithium metal negative electrode and the sulfide-based glass electrolyte layer, and the lithium metal negative electrode and the sulfide-based glass electrolyte layer were laminated. Also, it was found that there were no pores in the laminated layer, the lithium metal negative electrode, and the sulfide-based glass electrolyte layer.

[0085] Comparative Example 1 The same current collector and lithium metal foil as in Example 1 were used. After placing the lithium metal foil on the current collector, it was crimped and laminated to produce two laminates of the current collector and the lithium metal foil.

[0086] The laminate of the current collector and the lithium metal foil manufactured above was placed so that the lithium metal foil was in contact with both sides of the same sulfide-based glass electrolyte film as in Example 1, positioned between heating plates, and simply crimped under a pressure of 0.2 kgf / cm without heating the lithium metal foil and the sulfide-based electrolyte film for 30 minutes to produce a contact structure. A symmetric cell was manufactured in the same manner as in Example 1, except for this. 2 A symmetric cell was manufactured in the same manner as in Example 1, except that the laminate of the current collector and the lithium metal foil manufactured above was placed so that the lithium metal foil was in contact with both sides of the same sulfide-based glass electrolyte film as in Example 1, positioned between heating plates, and simply crimped under a pressure of 0.2 kgf / cm without heating the lithium metal foil and the sulfide-based electrolyte film for 30 minutes to produce a contact structure.

[0087] Measurement of Interface Resistance Regarding the symmetric cells obtained in Example 1 and Comparative Example 1, while changing the pressure to 0 kgf / cm 2 (without crimping), 0.1 kgf / cm 2 , 0.2 kgf / cm 2 and 0.3 kgf / cm 2 the interface resistance between the lithium metal negative electrode and the sulfide-based electrolyte layer was measured, and the results are shown in FIG. 5.

[0088] The interfacial resistance was measured using a potentiostat equipped by BioLogic Sciences Instruments. The measurement conditions were set by applying an AC voltage of 10 mV in the frequency range of 0.1 Hz to 7 MHz.

[0089] The comparison of the interfacial resistance is shown in Fig. 5. The heated laminate layer described in Example 1 showed an improvement of nearly 6 times that of the laminate described in the comparative example simply crimped at room temperature. Also, unlike the comparative example, the heated laminate showed a small dependence on the pressure applied during the electrochemical test. For example, when the applied pressure was increased to 0.0 - 0.3 kgf / cm 2 the interfacial resistance decreased to less than 3%.

[0090] As can be seen from Fig. 5, when the negative electrode of Comparative Example 1 was used, the interfacial resistance R1 without applying pressure was a very high 50000 Ω, and the interfacial resistance R2 when a pressure of 0.3 kgf / cm 2 was applied was 40000 Ω. Therefore, it was found that the pressure change was large when the symmetric cell was pressed or not pressed, and a continuously high pressure had to be maintained for the driving of the battery.

[0091] However, when the symmetric cell of Example 1 was used, the interfacial resistance R1 without applying pressure was 8000 Ω, showing a considerably lower value than that of Comparative Example 1. Also, the interfacial resistance R2 when a pressure of 0.3 kgf / cm 2 was applied was 7800 Ω, showing a considerably lower value than the interfacial resistance value of Comparative Example 1 when the same pressure was applied to the symmetric cell. When no pressure was applied to the symmetric cell obtained in Example 1 and when a pressure of 0.3 kgf / cm 2 was applied, the change rate of the interfacial resistance value was only about 3%, and it was found that the interfacial resistance was substantially the same whether pressure was applied or not. In the negative electrode - glass electrolyte layer laminate according to an exemplary embodiment, since the lithium - containing metal negative electrode and the glass electrolyte layer are laminated with excellent adhesion, it may be possible that no separate crimping is required to maintain the adhesion for the operation of the battery.

[0092] Although the foregoing exemplary embodiments have been shown and described, those skilled in the art can understand that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims

1. A negative electrode - glass electrolyte layer laminate including a negative electrode and a sulfide glass electrolyte layer on at least one surface of the negative electrode, wherein the negative electrode includes a surface - passivated lithium - containing metal foil directly laminated on the surface of the sulfide glass electrolyte layer. The interfacial resistance between the lithium-containing metal foil and the sulfide glass electrolyte layer decreases to less than 10% when a pressure of 0.3 kgf / cm ２ is applied to the laminate, a negative electrode-glass electrolyte layer laminate.

2. The negative electrode - glass electrolyte layer laminate according to Claim 1, wherein there are no pores at the interface between the negative electrode and the sulfide glass electrolyte layer.

3. The negative electrode - glass electrolyte layer laminate according to Claim 1, wherein the interface between the negative electrode and the glass electrolyte layer has a laminated layer composed of elemental constituent components of a lithium - containing metal and a sulfide glass electrolyte.

4. The negative electrode - glass electrolyte layer laminate according to Claim 3, wherein the laminated layer has a thickness greater than 0 μm and less than or equal to about 20 μm.

5. The negative electrode - glass electrolyte layer laminate according to Claim 3, wherein the laminated layer has a thickness of about 0.1 μm or more and about 5 μm or less.

6. The negative electrode - glass electrolyte layer laminate according to Claim 1, wherein the glass electrolyte layer is a monolithic electrolyte layer.

7. The negative electrode - glass electrolyte layer laminate according to Claim 1, wherein the glass electrolyte layer has a thickness of 200 μm or less.

8. A method for manufacturing a negative electrode - glass electrolyte layer laminate, comprising: providing a sulfide glass electrolyte sheet; providing a lithium - containing metal foil having a passivated surface; layering the sulfide glass electrolyte sheet on the passivated surface of the lithium - containing metal foil; performing heating and pressure bonding to laminate the lithium - containing metal foil and the glass electrolyte film, and when measured near the interface with the sulfide glass electrolyte, the homologous temperature of the lithium - containing metal foil is in the range of 0.85 to < 1.

9. The manufacturing method according to Claim 8, wherein the lamination is performed such that the homologous temperature is about 0.85 or about 0.9 or about 0.

95.

10. The lamination is carried out in a pressure range of 0.05 to 0.3 kgf / cm ２ according to the manufacturing method of claim 8.

11. The manufacturing method according to Claim 8, wherein the lamination is performed for 5 to 30 minutes.

12. An all - solid - state secondary battery including the negative electrode - glass electrolyte layer laminate according to Claim 1 and a positive electrode.

13. The all - solid - state secondary battery according to Claim 12, further including a solid electrolyte layer between the glass electrolyte layer of the negative electrode - glass electrolyte layer laminate and the positive electrode.

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