All-solid-state secondary battery and method for manufacturing the same

Abstract

The all-solid-state secondary battery includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, the negative electrode including a negative electrode current collector, a first negative electrode active material layer in contact with the negative electrode current collector and containing a first metal, a second negative electrode active material layer disposed between the first negative electrode active material layer and the solid electrolyte layer and containing a carbon-based active material, and a contact layer disposed between the second negative electrode active material layer and the solid electrolyte layer so as to block contact between the second negative electrode active material layer and the solid electrolyte layer, the contact layer including the second metal and having a thickness thinner than that of the first negative electrode active material layer.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state secondary battery and a method for manufacturing the same. [Background technology]

[0002] Recently, in response to industrial demands, batteries with high energy density and safety have been developed. For example, lithium-ion batteries have been put to practical use not only in the fields of information-related devices and communication devices but also in the field of automobiles. In the field of automobiles, the safety of lithium-ion batteries is particularly important.

[0003] Currently available lithium-ion batteries contain flammable organic solvents and electrolytes, which can overheat the organic solvent and cause a fire if a short circuit occurs. In response to this, all-solid-state secondary batteries have been proposed that contain solid electrolytes instead of electrolytes.

[0004] Since all-solid-state secondary batteries do not use flammable organic solvents, the possibility of fire or explosion can be significantly reduced even if a short circuit occurs, and therefore such all-solid-state batteries can be significantly safer than lithium-ion batteries that use liquid electrolytes.

[0005] To increase the energy density of such all-solid-state secondary batteries, lithium can be used as the negative electrode active material. For example, the capacity density (capacity per unit mass) of lithium is 10 times greater than that of graphite (which is sometimes used as a negative electrode active material). Therefore, by using lithium as the negative electrode active material, it is possible to increase the output power of all-solid-state secondary batteries while reducing their thickness.

[0006] However, there is a need for improved all-solid-state secondary batteries that are less likely to experience short circuits. Summary of the Invention [Problem to be solved by the invention]

[0007] One aspect of the present disclosure provides an all-solid-state secondary battery and a manufacturing method thereof that can reduce the interfacial resistance between the negative electrode layer and the solid electrolyte while preventing crack formation in the solid electrolyte. [Means for solving the problem]

[0008] An all-solid-state secondary battery according to one embodiment includes: a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode; The negative electrode is a negative electrode current collector; a first negative electrode active material layer in contact with the negative electrode current collector and containing a first metal; a second negative electrode active material layer disposed between the first negative electrode active material layer and the solid electrolyte layer and including a carbon-based active material; a contact layer disposed between the second negative electrode active material layer and the solid electrolyte layer so as to prevent contact between the second negative electrode active material layer and the solid electrolyte layer, The contact layer may include a second metal and may have a thickness less than that of the first negative electrode active material layer.

[0009] The first metal may include lithium metal or a lithium alloy, and the second metal may include lithium metal or a lithium alloy. The first metal and the second metal may be the same.

[0010] The thickness of the contact layer is also 20% or less of the thickness of the first negative electrode active material layer. The contact layer also has a thickness of 1 nm to 1 μm. The contact layer has a thickness smaller than that of the second negative electrode active material layer.

[0011] During charge / discharge cycles, the volume change rate of the first negative electrode active material layer is greater than the volume change rate of the contact layer.

[0012] During charge / discharge cycles, the volume change rate of the second negative electrode active material layer is greater than the volume change rate of the contact layer.

[0013] The volume of the contact layer in the charged state is 1.5 to 20 times the volume of the contact layer in the discharged state.

[0014] The volume of the first negative electrode active material layer in a charged state is 1.5 to 500 times the volume of the first negative electrode active material layer in a discharged state.

[0015] The volume of the second negative electrode active material layer in a charged state is larger than the volume of the second negative electrode active material layer in a discharged state, and the volume of the second negative electrode active material layer in a charged state is not more than twice the volume of the second negative electrode active material layer in a discharged state. The solid electrolyte layer also contains an oxide-based solid electrolyte.

[0016] A method for producing an all-solid-state secondary battery according to one embodiment includes: providing a positive electrode layer; providing a negative electrode layer; providing a solid electrolyte layer; bonding a negative electrode layer to one surface of the solid electrolyte layer; and bonding a positive electrode layer to the other surface of the solid electrolyte layer, The step of providing the negative electrode layer comprises: disposing a first layer including lithium metal or a lithium alloy disposed on a first substrate and a second layer including a carbon-based active material disposed on a second substrate; disposing the first layer and the second layer so that they face each other, and applying a pressure equal to or greater than a predetermined pressure so that the first substrate and the second substrate become closer to each other; In the process of pressing the first substrate and the second substrate together, A third layer including lithium metal or a lithium alloy may be formed between the second substrate and the second layer, and the third layer may have a thickness less than that of the first layer.

[0017] The second layer includes a metal capable of forming an alloy with lithium, and in the step of pressing the first substrate and the second substrate together, the metal capable of forming an alloy with lithium in the first layer and the third layer can form an alloy with lithium.

[0018] The step of providing the negative electrode layer may further include removing the second substrate after the third layer is formed.

[0019] In the step of pressing the first substrate and the second substrate together, the pressure applied is 150 MPa to 1,000 MPa.

[0020] A method for manufacturing a negative electrode layer of an all-solid-state secondary battery according to another embodiment includes the steps of: Providing a first layer including lithium metal or a lithium alloy disposed on a first substrate and a second layer including a carbon-based active material disposed on a second substrate; disposing the first layer and the second layer so that they face each other, and applying a pressure equal to or greater than a predetermined pressure so that the first substrate and the second substrate become closer to each other; In the step of pressing the first substrate and the second substrate together, A third layer containing lithium metal or a lithium alloy and having a thickness thinner than that of the first layer may be formed between the second substrate and the second layer.

[0021] The second layer includes a metal capable of forming an alloy with lithium, and in the step of pressing the first substrate and the second substrate together, the metal in the first layer and the third layer can form an alloy with lithium.

[0022] After the third layer is formed, the second substrate can be removed.

[0023] In the step of pressing the first substrate and the second substrate together, the pressure applied may be 150 MPa or more. [Effects of the Invention]

[0024] The all-solid-state secondary battery and the manufacturing method thereof according to this embodiment can reduce the interfacial resistance between the negative electrode layer and the solid electrolyte while preventing cracks in the solid electrolyte.

[0025] The above and other aspects, features, and advantages of particular embodiments of the disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings: [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view for explaining an all-solid-state secondary battery according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view for explaining the negative electrode layer of FIG. [Figure 3] FIG. 2 is a cross-sectional view for explaining charging of the negative electrode layer of the all-solid-state secondary battery according to the embodiment. [Figure 4] FIG. 2 is a cross-sectional view illustrating discharge of a negative electrode layer of an all-solid-state secondary battery according to an embodiment. [Figure 5A] 1 is a cross-sectional SEM (scanning electron microscope) image of a negative electrode layer after charging according to an embodiment. [Figure 5B] 1 is a cross-sectional SEM (scanning electron microscope) image of a negative electrode layer after discharge according to an embodiment. [Figure 6A] 5B is an enlarged view of a scanning electron microscope (SEM) image of FIG. 5A showing the periphery of the contact layer and the second negative electrode active material layer. [Figure 6B] 5C is an enlarged view of a scanning electron microscope (SEM) image of FIG. 5B showing the periphery of the contact layer and the second negative electrode active material layer. [Figure 7A] 1 is a diagram of an embodiment of a method for manufacturing a negative electrode layer. [Figure 7B] 1 is a diagram of an embodiment of a method for manufacturing a negative electrode layer. [Figure 7C] 1 is a diagram of an embodiment of a method for manufacturing a negative electrode layer. [Figure 7D] 1 is a diagram of an embodiment of a method for manufacturing a negative electrode layer. [Figure 8] 1 is a photograph showing a negative electrode layer according to an embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing a negative electrode layer according to a comparative example. [Figure 10] 10 is a photograph showing a negative electrode layer according to a comparative example. [Figure 11] 1 is a cross-sectional SEM (scanning electron microscope) image of a negative electrode layer according to an embodiment. [Figure 12] This is an enlarged image of a part of Figure 11. [Figure 13] This is an enlarged image of a part of Figure 12. [Figure 14] 1 is a Nyquist plot of imaginary impedance (Z″: ohm / cm2) versus real impedance (Z′: ohm / cm2) showing impedance measurement results for Comparative Examples 1 and 2 and Example 1. [Figure 15] 15 is an enlarged view of a part of FIG. 14. [Figure 16] 1 is a graph of potential (volts vs. Li / Li+) versus areal capacity (mAh / cm2) showing the charge / discharge curve of an all-solid-state secondary battery including a negative electrode layer according to Comparative Example 1. [Figure 17] 10 is a graph of potential (volts vs. Li / Li+) versus areal capacity (mAh / cm2) showing the charge / discharge curve of an all-solid-state secondary battery including a negative electrode layer according to Comparative Example 21. [Figure 18] 1 is a graph of potential (volts vs. Li / Li+) versus areal capacity (mAh / cm2) showing the charge / discharge curve of an all-solid-state secondary battery including a negative electrode layer according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings. In this regard, the embodiments may have different forms and are not to be construed as being limited to the description set forth herein. Accordingly, the embodiments will be described below with reference to the drawings, for illustrative purposes only.

[0028] When an element is referred to as being "on" another element, it will be understood that it may be directly on the other element, or that there may be intervening elements. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0029] The terms "first," "second," and "third" may be used herein to describe various elements, components, regions, layers, and / or sections, but such elements, components, regions, layers, and / or sections are not limited to such terms. Such terms are used only to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first "element," "component," "region," "layer," or "section" discussed below may also be referred to as a second "element," "component," "region," "layer," or "section" without departing from the teachings of this specification.

[0030] The terms used herein are merely used to describe particular embodiments and are not intended to be limiting. As used herein, the terms "a," "an," "the," and "at least one" do not denote limitations of quantity and are intended to include both the singular and the plural, unless the context clearly dictates otherwise. For example, "an element" has the same meaning as "at least one element" unless the context clearly dictates otherwise. "Or" means "and / or." As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Phrases such as "at least one of," when preceding a list of elements, modify the entire list of elements and not the individual elements of the list. It will be further understood that, as used herein, the terms "comprise" and / or "comprising," or "include" and / or "comprising" specify the presence of referenced features, regions, integers, steps, acts, or elements. "And / or" includes elements but does not exclude the presence or addition of one or more other features, regions, integers, steps, acts, elements, components, and / or groups thereof.

[0031] Spatially relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein to facilitate the description of the relationship of one element or feature to another element. It will also be understood that spatially relative terms are intended to include other orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures were turned upside down, elements described as "beneath" or "below" other elements or features would also be oriented "above" the other elements or features. Thus, the exemplary term "below" also encompasses both an up and down orientation. The device may also be oriented differently (rotated 90 degrees or to other orientations), and the spatially relative designators used herein should be interpreted accordingly.

[0032] As used herein, "about" or "approximately" means inclusive of the stated value and within an acceptable range of variation for the specified value as determined by one of ordinary skill in the art, taking into account the measurement and the error associated with the measurement. The specified quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or 5% of the stated value.

[0033] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. Furthermore, commonly used and predefined terms should be interpreted to have a meaning consistent with the meaning in the context of the relevant art and the contents of this disclosure, and should not be interpreted in an ideal meaning or in an overly formal meaning unless expressly defined herein.

[0034] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. Variations in the illustrated configurations are to be expected, for example, as a result of manufacturing techniques and / or tolerances. The embodiments described herein are not to be construed as limited to the particular shapes of regions illustrated herein and are to include, for example, deviations in shapes that arise during manufacturing. For example, a region illustrated or described as flat may generally have rough and / or non-linear features. Also, sharp angles illustrated may be rounded. Accordingly, regions illustrated in the figures are diagrammatic in nature, and their shapes are not intended to illustrate the precise shape of the region or to limit the scope of the claims.

[0035] Hereinafter, an all-solid-state secondary battery according to an embodiment, a negative electrode layer used therein, and a manufacturing method thereof will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals refer to the same components, and the size and thickness of each component may be exaggerated for ease of explanation. Note that the embodiment described below is merely illustrative, and various modifications are possible from such an embodiment.

[0036] In all-solid-state secondary batteries that use a solid electrolyte and contain lithium as the negative electrode active material, lithium metal may be unevenly deposited on the surface of the solid electrolyte during charging, which may lead to cracks in the solid electrolyte. The cracks in the solid electrolyte may result in short circuits in the all-solid-state secondary battery. This embodiment provides an all-solid-state secondary battery that includes a thin metal contact layer between the negative electrode active material layer and the solid electrolyte layer, minimizing the occurrence of cracks and short circuits.

[0037] Fig. 1 is a cross-sectional view for explaining an all-solid-state secondary battery 1 according to an embodiment, and Fig. 2 is a cross-sectional view for explaining the anode layer 20 in Fig. 1. Figs. 3 and 4 are drawings for explaining the effects of charging and discharging the anode layer 20 of the all-solid-state secondary battery 1.

[0038] 1 and 2, an all-solid-state secondary battery 1 according to an embodiment is a secondary battery including a solid electrolyte as an electrolyte. As an example, the all-solid-state secondary battery 1 is a so-called all-solid-state lithium-ion secondary battery in which lithium ions move between a positive electrode layer 10 and a negative electrode layer 20.

[0039] The all-solid-state secondary battery 1 includes a positive electrode layer 10 (also called a positive electrode), a solid electrolyte layer 30, and a negative electrode layer 20 (also called a negative electrode).

[0040] (positive electrode layer) The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 . The positive electrode current collector 11 may be a plate or foil containing, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), an alloy thereof, or a combination thereof. The positive electrode current collector 11 is optional.

[0041] The positive electrode active material layer 12 contains, for example, a positive electrode active material. The positive electrode active material is a positive electrode active material capable of reversibly absorbing and desorbing lithium ions. Examples of the positive electrode active material include, but are not limited to, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, lithium iron phosphate, or combinations thereof; nickel sulfide; copper sulfide; lithium sulfide; iron oxide; vanadium oxide; or combinations thereof. Any material known in the art as a positive electrode active material can be used. The positive electrode active material can be used alone or in combination, for example, as a mixture of two or more of these.

[0042] Lithium transition metal oxides include, for example, Li a A 1-b B' b D2 (wherein, in the formula, 0.90≦≦a≦1 and 0≦b≦0.5); Li a E 1-b B' b O 2-c D c (wherein, 0.90≦a≦1, 0≦b≦0.5, and 0≦c≦0.05); LiE2-b B' b O 4-c D c (wherein 0≦b≦0.5 and 0≦c≦0.05); Li a Ni 1-b-c Co b B' c D α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α≦2); Li a Ni 1-b-c Co b B' c O 2-α F' α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni 1-b-c Co b B' c O 2-α F'2 (wherein, in the formula, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni 1-b-c Mn b B' c D α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α≦2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni 1-b-c Mn b B' c O 2-α F'2 (wherein, in the formula, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, and 0<α<2); Li a Ni b E c G d O2 (wherein the formula is 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, and 0.001≦d≦0.1); Li a Ni b Co c Mn dGeO2 (wherein the formula is 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, and 0.001≦e≦0.1); Li a NiG b O2 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); Li a CoG b O2 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); Li a MnG b O2 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); Li a Mn2G b O4 (wherein the formula is 0.90≦a≦1, 0.001≦b≦0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li 3-f J2(PO4)3(0≦f≦2);Li 3-f Fe2(PO4)3 (0≦f≦2);LiFePO4. In such compounds, A is Ni, Co, Mn, or a combination thereof, B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, D is O, F, S, P, or a combination thereof, E is Co, Mn, or a combination thereof, F' is F, S, P, or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, Q is Ti, Mo, Mn, or a combination thereof, I' is Cr, V, Fe, Sc, Y, or a combination thereof, and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0043] Compounds with a coating layer added to the surface of such compounds can also be used, or mixtures of the aforementioned compounds with the aforementioned compounds with a coating layer added can also be used. Such compounds can be selected from among the aforementioned compounds. The coating layer can include, for example, at least one of the oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of the coating element. The compound forming such a coating layer can be amorphous or crystalline. Examples of coating elements included in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or combinations thereof. The method for forming the coating layer can be selected within a range that does not adversely affect the physical properties of the positive electrode active material. Examples of the coating method include spray coating and dipping. Specific coating methods are well understood by those skilled in the art, so detailed description is omitted.

[0044] The positive electrode active material includes, for example, a lithium transition metal oxide including a lithium salt of a transition metal oxide having a layered rock salt type structure. The term "layered rock salt type structure" refers to, for example, a cubic rock salt type structure. <111> In this structure, oxygen atomic layers and metal atomic layers are regularly arranged in the direction of the crystal structure, so that each atomic layer forms a two-dimensional plane. The term "cubic rock salt structure" refers to a sodium chloride (NaCl) type structure, which is a type of crystal structure, and specifically refers to a structure in which face-centered cubic lattices (FCC) formed by cations and anions are shifted from each other by about half the ridge of a unit lattice. Lithium transition metal oxides having such a layered rock salt structure include, for example, LiNi x Co y Al z O2(NCA) or LiNi x Coy Mn z It is a ternary lithium transition metal oxide such as O2(NCM)(0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1). When the positive electrode active material includes a ternary lithium transition metal oxide having a layered rock salt structure, the energy density and thermal stability of the all-solid-state secondary battery 1 are further improved.

[0045] As described above, the positive electrode active material also includes a coating layer. The coating layer may be any one as long as it is known as the coating layer of the positive electrode active material of the all-solid-state secondary battery 1, and is not limited. The coating layer is, for example, Li2O-ZrO2 or the like.

[0046] When the positive electrode active material contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the all-solid-state secondary battery 1 can be increased, and metal elution of the positive electrode active material can be reduced in the charged state. As a result, the cycle characteristics of the all-solid-state secondary battery 1 in the charged state are improved.

[0047] The shape of the positive electrode active material is, for example, a particle shape such as a true spherical shape or an elliptical spherical shape. The particle size of the positive electrode active material is not particularly limited and is within a range suitable for the positive electrode active material of the all-solid-state secondary battery 1. The content of the positive electrode active material in the positive electrode layer 10 is also not particularly limited and is within a range suitable for the positive electrode layer 10 of the conventional all-solid-state secondary battery 1.

[0048] In addition to the aforementioned positive electrode active material, the positive electrode layer 10 can further contain additives such as a conductive agent, binder, filler, dispersant, and ion-conducting aid. Examples of such conductive agents include graphite, carbon black (CB), acetylene black (AB), ketjen black (KB), carbon fiber, metal powder, or a combination thereof. Examples of the binder include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or a combination thereof. The coating agents, dispersants, and ion-conducting aids that can be incorporated into the positive electrode layer 10 are also suitable for use in electrodes of solid-state secondary batteries.

[0049] The positive electrode layer 10 may further include a solid electrolyte. The solid electrolyte included in the positive electrode layer 10 may be similar to or different from the solid electrolyte included in the solid electrolyte layer 30. For details regarding the solid electrolyte, please refer to the section on the solid electrolyte layer 30.

[0050] The solid electrolyte included in the positive electrode layer 10 is, for example, a sulfide-based (e.g., sulfide-containing) solid electrolyte. The sulfide-based solid electrolyte is also used as the sulfide-based solid electrolyte of the solid electrolyte layer 30.

[0051] Alternatively, the positive electrode layer 10 may be impregnated with a liquid electrolyte, for example. The liquid electrolyte may include a lithium salt and one or more of an ionic liquid and a polymeric ionic liquid. The liquid electrolyte may also be nonvolatile. The ionic liquid has a melting point below room temperature and refers to a salt that is in a liquid state at room temperature and is composed only of ions, or a room-temperature molten salt. The ionic liquid is one selected from compounds containing: a) a cation selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, solfonium, triazolium, and combinations thereof; and b) an anion selected from BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, BF4-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. The ionic liquid is, for example, one or more selected from the group consisting of N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, or a combination thereof.The polymeric ionic liquid comprises: a) a cation selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, solfonium, triazolium, or a combination thereof; and b) a cation selected from BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, (CF3SO2)2N-, (FSO2)2N-, Cl-, Br-, I-, SO4-, CF3 and a repeating unit containing an anion selected from SO3-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, NO3-, Al2Cl7-, (CF3SO2)3C-, (CF3)2PF4-, (CF3)3PF3-, (CF3)4PF2-, (CF3)5PF-, (CF3)6P-, SF5CF2SO3-, SF5CHFCF2SO3-, CF3CF2(CF3)2CO-, CF3SO2)2CH-, (SF5)3C-, (O(CF3)2C2(CF3)2O)2PO-, or a combination thereof. The lithium salt may be any suitable material for the lithium salt, and is not limited thereto. The lithium salts include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C. x F 2x+1 SO2)(C y F 2y+1 SO2) (where x and y are natural numbers), LiCl, LiI, or a combination thereof. The concentration of the lithium salt contained in the liquid electrolyte is about 0.1 M to about 5 M, or about 0.05 M to about 4.0 M, or about 0.1 M to about 3.0 M, or about 0.5 M to about 2.0 M, or about 0.5 M to about 1.5 M. The content of the liquid electrolyte impregnated into the positive electrode layer 10 is 0 to 100 parts by weight, 0 to 50 parts by weight, 0 to 30 parts by weight, 0 to 20 parts by weight, 0 to 10 parts by weight, or 0 to 5 parts by weight per 100 parts by weight of the positive electrode active material layer 12 not including the liquid electrolyte.

[0052] (solid electrolyte layer) The solid electrolyte layer 30 is disposed between the positive electrode layer 10 and the negative electrode layer 20. The solid electrolyte layer 30 includes a solid electrolyte.

[0053] The solid electrolyte may be, for example, an oxide-based (e.g., oxygen-containing) inorganic solid electrolyte. The oxide-based solid electrolyte may be Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2、0≦y<3)、BaTiO3、Pb(Zr、Ti)O3(PZT)、Pb 1-x La x Zr 1-y Ti y O3(PLZT)(O≦x<1, O≦y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2、0<y<3)、Li x Al y Ti z (PO4)3(0 <x<2、0<y<1、0<z<3)、Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≦x≦10≦y≦1), Li x La y TiO3(0 <x<2、0<y<3)、Li2O、LiOH、Li2CO3、LiAlO2、Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2、Li 3+x La3M2O 12 (M is Te, Nb or Zr, and x is an integer of 1 to 10), or a combination thereof. The solid electrolyte is produced by a sintering method or the like.

[0054] The oxide-based solid electrolyte is, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M doped LLZO; M is Ga, W, Nb, Ta or Al, and x is an integer from 1 to 10).

[0055] Alternatively, the solid electrolyte may be, for example, a sulfide-based solid electrolyte, such as LiS-P2S5, LiS-P2S5-LiX (X is a halogen element), LiS-P2S5-Li2O, LiS-P2S5-Li2O-LiI, LiS-SiS2, LiS-SiS2-LiI, LiS-SiS2-LiBr, LiS-SiS2-LiCl, LiS-SiS2-B2S3-LiI, LiS-SiS2-P2S5-LiI, LiS-B2S3, or LiS-P2S5-Z. m S n (m and n are integers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are integers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 7-x PS 6-x Cl x (0≦x≦2), Li 7-x PS 6-x Br x (0≦x≦2), and Li 7-x PS 6-x I x (0≦x≦2), or a combination thereof. The sulfide-based solid electrolyte is prepared by processing starting materials such as Li2S and P2S5 by melt quenching or mechanical milling. After such processing, heat treatment can be performed. The sulfide-based solid electrolyte can be amorphous, crystalline, or a mixture of these. The sulfide-based solid electrolyte may contain, for example, sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the sulfide-based solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5, the molar ratio of Li2S to P2S5 is, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0056] The sulfide solid electrolyte is Li 7-x PS 6-x Cl x (0≦x≦2), Li 7-x PS 6-x Br x (0≦x≦2) or Li 7-x PS 6-x I x (0≦x≦2), or argyrodite-type compounds including combinations thereof. In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including Li6PS5Cl, Li6PS5Br, Li6PS5I, or combinations thereof.

[0057] The solid electrolyte layer 30 further includes, for example, a binder. The binder included in the solid electrolyte layer 30 can be any suitable binder, including, but not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or a combination thereof. The binder of the solid electrolyte layer 30 can be the same as or different from the binder of the positive electrode layer and / or the negative electrode layer.

[0058] (negative electrode layer) 1 and 2, the negative electrode layer 20 includes a negative electrode current collector 21, a negative electrode active material layer 22, and a contact layer .

[0059] During the charging process of the all-solid-state secondary battery 1, the volume of the negative electrode layer 20 can increase, as can be seen from Fig. 3. During the discharging process of the all-solid-state secondary battery 1, the volume of the negative electrode layer 20 can decrease, as can be seen from Fig. 4.

[0060] The negative electrode current collector 21 may be made of, for example, a material that does not react with lithium, i.e., a material that does not form an alloy or compound. The material constituting the negative electrode current collector 21 may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or a combination thereof, but is not necessarily limited thereto. Any material used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector 21 may also include an alloy or coating material of one or more of the aforementioned metals. The negative electrode current collector 21 may be, for example, in the form of a plate or foil.

[0061] The negative electrode active material layer 22 includes a first negative electrode active material layer 221 and a second negative electrode active material layer 222. The first negative electrode active material layer 221 is disposed on the negative electrode current collector 21 and contains a first metal. The first negative electrode active material layer 221 is also a first metal layer. The first metal includes lithium metal or a lithium alloy. Therefore, since the first negative electrode active material layer 221 is a metal layer containing lithium or a lithium alloy, it acts as, for example, a lithium reservoir.

[0062] The lithium metal can be metallic lithium, which is a metal containing lithium (Li) but not containing any metal that can be alloyed with lithium. The lithium alloy can be, for example, a Li-Ag alloy, a Li-Au alloy, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, or a combination thereof, but is not limited thereto. Any material suitable for use as a lithium alloy can be used. The first negative electrode active material layer 221 can contain either a lithium alloy or lithium metal, or a combination of various alloys. The thickness t1 of the first negative electrode active material layer 221 can be 10 μm or greater. For example, the thickness t1 of the first negative electrode active material layer 221 can be 10 μm to 1,000 μm, 10 μm to 500 μm, 10 μm to 200 μm, 10 μm to 150 μm, 10 μm to 100 μm, or 10 μm to 50 μm. If the thickness t1 of the first negative electrode active material layer 221 is too thin, it is difficult for the first negative electrode active material layer 221 to function as a lithium reservoir. If the thickness t1 of the first negative electrode active material layer 221 is too thick, the mass and volume of the all-solid-state secondary battery 1 increase, which may result in a decrease in cycle characteristics.

[0063] The first negative electrode active material layer 221 is disposed between the negative electrode current collector 21 and the second negative electrode active material layer 222. When the all-solid-state secondary battery 1 is charged, lithium is deposited in the first negative electrode active material layer 221, and the volume or thickness of the first negative electrode active material layer 221 increases due to the deposited lithium.

[0064] The volume of the first negative electrode active material layer 221 in the charged state is 150% to 5,000% of the volume of the first negative electrode active material layer 221 in the discharged state. The thickness of the first negative electrode active material layer 221 in the charged state is 150% to 5,000% of the thickness of the first negative electrode active material layer 221 in the discharged state.

[0065] During a charge / discharge process (e.g., a charge / discharge cycle), the volume change rate of the first negative electrode active material layer 221 is greater than that of the contact layer 23. During the charge / discharge process, the volume change rate of the first negative electrode active material layer 221 is greater than that of the second negative electrode active material layer 222. During the charge / discharge process, the thickness change rate of the first negative electrode active material layer 221 is greater than that of the contact layer 23. During the charge / discharge process, the thickness change rate of the first negative electrode active material layer 221 is greater than that of the second negative electrode active material layer 222.

[0066] The second negative electrode active material layer 222 is disposed between the first negative electrode active material layer 221 and the solid electrolyte layer 30, and contains a carbon-based (eg, containing carbon) active material.

[0067] The carbon-based active material may also include amorphous carbon, such as carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, carbon nanotubes, carbon nanofibers, or a combination thereof, but is not limited thereto, and any material classified as amorphous carbon in the art may be used.

[0068] The second negative electrode active material layer 222 also contains a metal or semi-metal as the negative electrode active material, where "semi-metal" means B, Si, Ge, As, Sb, Te, or a combination thereof.

[0069] The metal or metalloid negative electrode active material includes, but is not necessarily limited to, indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), palladium (Pd), silver (Ag), zinc (Zn), or a combination thereof, and can be any metal or metalloid negative electrode active material that forms an alloy or compound with lithium and is used as the metal or metalloid negative electrode active material.

[0070] The second negative electrode active material layer 222 includes a negative electrode active material including a carbon-based active material, a metal or semimetallic negative electrode active material, or a combination of a carbon-based negative electrode active material and a metal or semimetallic negative electrode active material. For example, the second negative electrode active material layer 222 includes only amorphous carbon, or includes indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), palladium (Pd), silver (Ag), zinc (Zn), or a combination thereof. Alternatively, the second negative electrode active material layer 222 may include a composite of amorphous carbon and a metal or metalloid, such as indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), or a combination thereof. The weight ratio of the composite of amorphous carbon and the metal (e.g., silver) or metalloid is, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to such ranges and can be determined by one skilled in the art depending on the desired characteristics of the all-solid-state secondary battery 1. When the second negative electrode active material layer 222 has such a composition, the cycle characteristics of the all solid state secondary battery 1 are further improved.

[0071] The negative electrode active material of the second negative electrode active material layer 222 includes, for example, a mixture of first particles of amorphous carbon and second particles of a metal or metalloid. The mixture can consist essentially of, or include, a dispersion of the first particles and the second particles. In another example, the mixture can further include a binder, which physically binds the first particles and the second particles. The metal or metalloid can include, for example, indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), or a combination thereof. The metal or metalloid can also be a semiconductor. The content of the second particles is 8 to 60 wt %, 10 to 50 wt %, 15 to 40 wt %, or 20 to 30 wt %, based on the total weight of the mixture. When the second particles have a content in such a range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0072] The thickness t2 of the second negative electrode active material layer 222 is, for example, 10 nm to 10 μm, 100 nm to 10 μm, 200 nm to 10 μm, 300 nm to 10 μm, 400 nm to 10 μm, 500 nm to 10 μm, 1 μm to 10 μm, 1 μm to 9 μm, 1 μm to 8 μm, 2 μm to 7 μm, or 3 μm to 7 μm. When the second negative electrode active material layer 222 has a thickness in such a range, short circuits in the all-solid-state secondary battery 1 are suppressed and the cycle characteristics are improved.

[0073] The thickness t2 of the second negative electrode active material layer 222 is thinner than the thickness t1 of the first negative electrode active material layer 221. The thickness t2 of the second negative electrode active material layer 222 is thinner than half the thickness t1 of the first negative electrode active material layer 221. The thickness t2 of the second negative electrode active material layer 222 is thinner than 20% of the thickness t1 of the first negative electrode active material layer 221.

[0074] Since the second negative electrode active material layer 222 includes a carbon-based active material, the second negative electrode active material layer 222 may have a characteristic of changing its volume in response to a change in the volume of the first negative electrode active material layer 221. For example, when the first negative electrode active material layer 221 expands during charging, the second negative electrode active material layer 222 can absorb and mitigate the volume expansion of the first negative electrode active material.

[0075] The second anode active material layer 222 contains a carbon-based active material, and thus has voids or pores therein. The second anode active material layer 222 in a discharged state also has voids or pores formed therein. During charging, lithium fills the voids in the second anode active material layer 222, thereby mitigating the volumetric expansion of the first anode active material layer 221. By mitigating the volumetric expansion of the first anode active material layer 221, the pressure applied by the anode layer 20 to the solid electrolyte layer 30 is reduced, thereby delaying the short-circuiting phenomenon of the solid electrolyte layer 30.

[0076] The volume of the second anode active material layer 222 in the charged state is larger than the volume of the second anode active material layer 222 in the discharged state. The volume of the second anode active material layer 222 in the charged state is also not more than twice the volume of the second anode active material layer 222 in the discharged state. The thickness t21 of the second anode active material layer 222 in the charged state is thicker than the thickness t22 of the second anode active material layer 222 in the discharged state. The thickness t21 of the second anode active material layer 222 in the charged state is also not more than twice the thickness t22 of the second anode active material layer 222 in the discharged state.

[0077] As described above, when the second anode active material layer 222 contains a carbon-based active material, it has the property of mitigating the volume expansion of the first anode active material layer 221, but has the property of poor interfacial adhesion with the solid electrolyte layer 30. Therefore, when the second anode active material layer 222 is disposed so as to be in direct contact with the solid electrolyte layer 30, a problem occurs in that the interfacial resistance between the anode layer 20 and the solid electrolyte layer 30 increases.

[0078] In consideration of this, the negative electrode layer 20 of the all-solid-state secondary battery 1 according to one embodiment includes a contact layer 23 disposed between the second negative electrode active material layer 222 and the solid electrolyte layer 30.

[0079] At least a portion of the contact layer 23 is disposed between the second anode active material layer 222 and the solid electrolyte layer 30, and is in direct contact with the solid electrolyte layer 30. The contact layer 23 is in direct contact with the solid electrolyte layer 30, thereby blocking direct contact between the second anode active material layer 222 and the solid electrolyte layer 30. The contact layer 23 is disposed between the second anode active material layer 222 and the solid electrolyte layer 30, and is disposed so as to prevent contact between the anode active material layer and the solid electrolyte layer 30. As a result, the contact-improving layer 23 can improve the interfacial adhesion between the anode layer 20 and the solid electrolyte layer 30.

[0080] The interface resistance between the contact layer 23 and the solid electrolyte layer 30 is also a predetermined value or less. For example, the interface resistance between the contact layer 23 and the solid electrolyte layer 30 is 500 ohm cm. 2 Less than 400 ohm cm 2 Less than 300 ohm cm 2 For example, the interface resistance between the contact layer 23 and the solid electrolyte layer 30 is less than 200 ohm cm. 2 is smaller than.

[0081] The interface resistance of the contact layer 23 with the solid electrolyte layer 30 is smaller than the interface resistance between the second negative electrode active material layer 222 and the solid electrolyte layer 30. For example, the interface resistance between the contact layer 23 and the solid electrolyte layer 30 is smaller than 10% (1 / 10) of the interface resistance between the second negative electrode active material layer 222 and the solid electrolyte layer 30. For example, when the second negative electrode active material layer 222 is in direct contact with the solid electrolyte layer 30, the interface resistance therebetween is 2,000 ohm cm. 2 In the case where the contact layer 23 is in direct contact with the solid electrolyte layer 30, the interface resistance therebetween is 200 ohm cm. 2 is smaller than.

[0082] The contact layer 23 also includes a second metal layer, which may include lithium metal or a lithium alloy.

[0083] Lithium metal refers to metallic lithium, i.e., composed of lithium, and does not include metals that can alloy with lithium.

[0084] The lithium alloy includes lithium and a metal capable of alloying with lithium, such as, but not limited to, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, or a combination thereof, and may be any material known in the art as a suitable lithium alloy.

[0085] The contact layer 23 may comprise one of a lithium alloy, or lithium metal, or may comprise a combination of various types of alloys.

[0086] The second metal may be the same material as the first metal, but the material of the second metal is not limited thereto and may be different from the material of the first metal.

[0087] The contact layer 23 may, for example, not contain a carbon-based material. The contact layer 23 may, for example, not contain a carbon-based material such as a carbon-based active material, such as graphite or carbon black, or a carbon-based conductive material, such as carbon nanofiber. The contact layer 23 may, for example, not contain an organic material, such as a binder. The contact layer 23 may, for example, contain a metal layer made of a metal, a semi-metal, or an alloy thereof. Because the contact layer 23 is a metal layer and does not contain a carbon-based material, side reactions caused by the carbon-based material and / or organic material during the charge / discharge process (charge / discharge cycle) are prevented.

[0088] Furthermore, since the contact layer 23 includes the second metal layer but does not include a carbon-based material, it forms an interface with the solid electrolyte layer 30 that has superior adhesive strength compared to the second negative electrode active material layer 222 that includes a carbon-based active material.

[0089] Because the contact layer 23 contains the second metal, it induces rapid diffusion of lithium ions that flow in through the solid electrolyte layer 30 during charging. Therefore, even if the surface of the solid electrolyte layer 30 is irregular and lithium ions are locally concentrated and flow into the solid electrolyte layer, they can be evenly distributed throughout the anode layer 20 by utilizing the rapid diffusion phenomenon through the contact layer 23.

[0090] The contact layer 23 is also configured so that the amount of metal, for example, lithium metal or a lithium alloy, deposited in the first negative electrode active material layer 221 is smaller than the amount of the first metal during charging.

[0091] The thickness t3 of the contact layer 23 is a predetermined thickness or less. For example, the thickness t3 of the contact layer 23 is 1 μm or less. For example, the thickness t3 of the contact layer 23 is 0.5 μm or less. For example, the thickness t3 of the contact layer 23 is 0.1 μm or less. However, if the thickness t3 of the contact layer 23 is excessively thin, it becomes difficult to achieve the original purpose of the second negative electrode active material layer 222 being in direct contact with the solid electrolyte layer 30. Therefore, the thickness t3 of the contact layer 23 is 1 nm or more. The thickness of the contact layer 23 is 1 nm to 1 μm, 1 nm to 500 nm, 1 nm to 100 nm, or 1 nm to 50 nm. The thickness of the contact layer 23 may be uniform or non-uniform. Here, when the thickness t3 of the contact layer 23 is not uniform, the thickness t3 of the contact layer 23 is defined as the average thickness of the contact layer 23.

[0092] The thickness t3 of the contact layer 23 is thinner than the thickness t1 of the first negative electrode active material layer 221. For example, the thickness t31 of the contact layer 23 in the post-discharge state is thinner than the thickness t12 of the first negative electrode active material layer 221 in the post-discharge state. When the thickness t12 of the first negative electrode active material layer 221 in the post-discharge state exceeds 10 μm, the thickness t32 of the contact layer 23 in the post-discharge state is also 1 μm or less.

[0093] The thickness t3 of the contact layer 23 is also 20% (1 / 5) or less of the thickness t1 of the first negative electrode active material layer 221. The thickness t3 of the contact layer 23 is also 10% (1 / 10) or less of the thickness t1 of the first negative electrode active material layer 221. The thickness t3 of the contact layer 23 is also 5% (1 / 20) or less of the thickness t1 of the first negative electrode active material layer 221.

[0094] The thickness t32 of the contact layer 23 in the post-discharge state is also 20% (1 / 5) or less of the thickness t12 of the first negative electrode active material layer 221 in the post-discharge state. The thickness t32 of the contact layer 23 in the post-discharge state is also 10% (1 / 10) or less of the thickness t12 of the first negative electrode active material layer 221 in the post-discharge state. The thickness t32 of the contact layer 23 in the post-discharge state is also 5% (1 / 20) or less of the thickness t12 of the first negative electrode active material layer 221 in the post-discharge state.

[0095] The thickness t31 of the contact layer 23 in the charged state is also 10% (1 / 10) or less of the thickness t11 of the first negative electrode active material layer 221 in the charged state. The thickness t31 of the contact layer 23 in the charged state is also 5% (1 / 20) or less of the thickness t11 of the first negative electrode active material layer 221 in the charged state. The thickness t31 of the contact layer 23 in the charged state is also 2.5% (1 / 40) or less of the thickness t11 of the first negative electrode active material layer 221 in the charged state.

[0096] In this way, by designing the thickness t3 of the contact layer 23 to be equal to or less than a predetermined thickness and the thickness t1 of the first negative electrode active material layer 221 to be thicker than the thickness of the contact layer 23, the amount of metal precipitated in the contact layer 23 can be reduced during the charging process of the all-solid-state secondary battery 1, and metal can be induced to precipitate in the first negative electrode active material layer 221.

[0097] If the thickness t3 of the contact layer 23 is greater than a predetermined value, the amount of lithium metal locally deposited on the contact layer 23 may increase during charging, which may cause cracks in the solid electrolyte layer 30.

[0098] In particular, when the solid electrolyte layer 30 includes an oxide solid electrolyte, which is harder than a sulfide solid electrolyte, the lithium metal locally deposited on the contact layer 23 may cause cracks in the solid electrolyte layer 30, which may lead to a problem of the lithium metal penetrating through the solid electrolyte 30. The penetration of the lithium metal through the solid electrolyte layer 30 may induce a short circuit, reducing the stability of the all-solid-state secondary battery 1.

[0099] Furthermore, due to the lithium metal locally deposited on the contact layer 23, empty spaces are formed between the contact layer 23 and the solid electrolyte layer 30 during repeated charge and discharge processes, reducing the contact area between the contact layer 23 and the solid electrolyte layer 30, which leads to overvoltage of the all-solid-state secondary battery 1.

[0100] However, in the all solid state secondary battery 1 according to one embodiment, the amount of lithium metal deposited in the contact layer 23 can be minimized by depositing metal in the first negative electrode active material layer 221. As a result, short circuits and overvoltage of the all solid state secondary battery 1 can be prevented.

[0101] By minimizing the amount of lithium deposited on the contact layer 23 during charging, the volume change rate of the contact layer 23 during charging and discharging is reduced.

[0102] For example, the volume of the contact layer 23 in the charged state is 150% or less of the volume of the contact layer 23 in the discharged state. The volume of the contact layer 23 in the charged state is 140% or less of the volume of the contact layer 23 in the discharged state. The volume of the contact layer 23 in the charged state is 130% or less of the volume of the contact layer 23 in the discharged state.

[0103] For example, during charge and discharge, the volume change rate of the contact layer 23 is smaller than the volume change rate of the first negative electrode active material layer 221. During charge and discharge, the volume change rate of the contact layer 23 is also approximately 70% or less of the volume change rate of the first negative electrode active material layer 221. During charge and discharge, the volume change rate of the contact layer 23 is also approximately 60% or less of the volume change rate of the first negative electrode active material layer 221. The volume change rate of the contact layer 23 is approximately 5% to approximately 70% of the volume change rate of the first negative electrode active material layer 221, or approximately 10% to approximately 60% of the volume change rate of the first negative electrode active material layer 221, or approximately 10% to approximately 50% of the volume change rate of the first negative electrode active material layer 221.

[0104] The second metal of the contact layer 23 may be the same as the first metal of the first negative electrode active material layer 221. For example, the second metal and the first metal may both be lithium metal. For example, the second metal and the first metal may both be lithium alloys, and the metals that form an alloy with lithium may be the same.

[0105] However, the second metal does not necessarily have to be the same as the first metal, and may differ depending on the manufacturing method or requirements.

[0106] 5A and 5B are cross-sectional SEM (scanning electron microscope) images of the negative electrode layer 20 according to one embodiment after charging and after discharging, and FIGS. 6A and 6B are enlarged cross-sectional SEM images of the contact layer 23 and the second negative electrode active material layer 222 in FIGS. 5A and 5B, respectively.

[0107] 5A and 5B, the thickness t11 of the first negative electrode active material layer 221 in the charged state is approximately 32 μm to 34 μm, and the thickness t12 of the first negative electrode active material layer 221 in the discharged state is approximately 17 μm to 18 μm.

[0108] 6A and 6B, the thickness t21 of the second negative electrode active material layer 222 in the charged state is 5 μm to 6 μm, and the thickness t22 of the second negative electrode active material layer 222 in the discharged state is also 5 μm to 6 μm. Furthermore, the thickness t31 of the contact layer 23 in the charged state is 0.5 μm to 1.5 μm, and the thickness t32 of the contact layer 23 in the discharged state is also 0.5 μm to 1.5 μm.

[0109] Therefore, it can be seen that in the negative electrode layer 20 according to one embodiment, the thickness change rate of the contact layer 23 and the thickness change rate of the second negative electrode active material layer 222 are each smaller than the thickness change rate of the first negative electrode active material layer 221 during the charge / discharge process.

[0110] A method for manufacturing an all-solid-state secondary battery 1 according to one embodiment includes the steps of providing an anode layer 20, disposing the anode layer 20 on one surface of a solid electrolyte layer 30, and disposing a cathode layer 10 on the other surface of the solid electrolyte layer 30.

[0111] (Production of negative electrode layer 20) 7A to 7D are diagrams illustrating a method for manufacturing the negative electrode layer 20. FIG. Referring to FIG. 7A, a first layer 321 formed on a first substrate 100 is prepared.

[0112] The first layer 321 may include a metal layer. The metal layer may include lithium metal, a lithium alloy, or a combination thereof. The lithium alloy may include, but is not limited to, a Li-Ag alloy, a Li-Au alloy, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, or a combination thereof, as long as the material is suitable for use as a lithium alloy.

[0113] The first layer 321 may be made of a lithium alloy or lithium metal, or may be made of a combination of lithium alloys.

[0114] The thickness of the first layer 321 is between 1 μm and 1,000 μm, between 1 μm and 500 μm, between 1 μm and 200 μm, between 1 μm and 150 μm, between 1 μm and 100 μm, or between 1 μm and 50 μm.

[0115] The first substrate 100 is made of, for example, a material that does not react with lithium, i.e., does not form any alloys or compounds. Materials for the first substrate 100 include, but are not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), alloys thereof, or combinations thereof. Any material that can function as an electrode current collector is acceptable. The first substrate 100 may be made of one of the aforementioned metals, or an alloy or coating material of two or more metals. The first substrate 100 is, for example, in the form of a plate or foil. The first substrate 100 also serves as the negative electrode current collector 21.

[0116] The second layer 322 is disposed on a second substrate. The second layer 322 may also include a carbon-based active material. Examples of the carbon-based active material include amorphous carbon. Examples of the amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, carbon nanotubes, carbon nanofibers, or combinations thereof. Any material classified as amorphous carbon is acceptable. The second layer 322 may further include a metal capable of forming an alloy with lithium. Examples of the metal capable of forming an alloy with lithium include silver (Ag), gold (Au), aluminum (Al), tin (Sn), indium (In), zinc (Zn), germanium (Ge), silicon (Si), or a combination thereof. However, the second layer 322 is not limited to these, and any metal capable of forming an alloy with lithium may be used. The metal capable of forming an alloy with lithium may be omitted from the second layer 322.

[0117] To form the second layer 322 on the second substrate 200, a carbon-based active material, a metal capable of being alloyed with lithium, a binder, etc. may be mixed to prepare a slurry, which may then be uniformly coated on the second substrate 200 and dried. The second layer 322 may also function as a precursor of the second negative electrode active material layer 222.

[0118] The second substrate 200 may be made of, for example, a material that does not react with lithium, i.e., a material that does not form any alloys or compounds with lithium. The second substrate 200 may also include a material having a predetermined strength of 500 MPa or more. For example, the material of the second substrate 200 may include stainless steel. However, the material of the second substrate 200 is not limited thereto, and may also include a material that does not react with lithium, such as copper (Cu), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or a combination thereof. The second substrate 200 may be, for example, in the form of a plate or foil.

[0119] Referring to FIG. 7B, after the first layer 321 and the second layer 322 are arranged to face each other, the first substrate 100 and the second substrate 200 can be pressed together with a predetermined pressure.

[0120] For example, the first substrate 100 and the second substrate 200 may be pressed together by the pressure plates 1001 and 1002. The pressure plates 1001 and 1002 are made of a material having a predetermined strength so as to press the first substrate 100 and the second substrate 200 together with a predetermined pressure. For example, the pressure plates 1001 and 1002 may be made of stainless steel. However, the material of the pressure plates 1001 and 1002 is not limited to stainless steel.

[0121] The first layer 321 and the second layer 322 are tightly attached and assembled by the application of pressure. The pressing may be, for example, roll pressing, uni-axial pressing, flat pressing, warm isotactic pressing (WIP), cold isotactic pressing (CIP), etc., but is not necessarily limited to such methods, and any appropriate pressing method is possible.

[0122] The pressure applied during pressurization may be, for example, 150 MPa or more. The pressure applied during pressurization may be, for example, 250 MPa or more. The pressure applied during pressurization may be, for example, 1,000 MPa or less. The pressure applied during pressurization may be, for example, 150 MPa to 1,000 MPa, 250 MPa to 1,000 MPa, or 250 MPa to 750 MPa.

[0123] The pressure may be applied for 10 minutes or less, 8 minutes or less, 5 minutes or less, 1 minute or less, or 30 seconds or less. For example, the pressure may be applied for 5 milliseconds (ms) to 10 minutes (min), 1 second to 7 minutes, or 30 seconds to 7 minutes. For example, the pressure may be applied for 2 minutes to 7 minutes.

[0124] The pressurization may be carried out at room temperature, for example, or at a temperature of 15°C to 25°C. However, the pressurization temperature is not necessarily limited thereto, and may be 25°C to 90°C or a high temperature of 100°C or higher.

[0125] 7C, when first layer 321 and second layer 322 are pressed together at a pressure equal to or greater than a predetermined pressure, contact layer 23, which is a third layer made of the same material as the metal layer included in first layer 321, is formed between second substrate 200 and second layer 322. Without being bound by theory, the formation of contact layer 23 is understood to be the result of a portion of first layer 321 being transferred through second layer 322.

[0126] When the first layer 321 contains lithium metal and the second layer 322 contains a metal capable of forming an alloy with lithium, the metal contained in the second layer 322 reacts with the lithium of the first layer 321 and the contact layer 23 during the pressurization process to form an alloy layer. As a result, the first layer 321 becomes the first negative electrode active material layer 221 containing a lithium alloy, and the contact layer 23 also becomes the contact layer 23 containing a lithium alloy.

[0127] If the second layer 322 does not contain a metal capable of alloying with lithium, the first layer 321 becomes the first negative electrode active material layer 221 containing lithium metal, and the contact layer 23 also becomes the contact layer 23 containing lithium metal.

[0128] In addition, in the process of pressurizing the first layer 321 and the second layer 322 at a pressure equal to or greater than a predetermined pressure, a portion of the lithium contained in the first layer 321 may be injected into the second layer 322. As a result, the second layer 322 also becomes the second negative electrode active material layer 222 containing the carbon-based active material and lithium.

[0129] Referring to FIG. 7D, by removing the second substrate 200, the negative electrode layer 20 may be provided on the first substrate 100, in which the first negative electrode active material layer 221, the second negative electrode active material layer 222, and the contact layer 23 are sequentially stacked.

[0130] 8 is a photograph showing an anode layer 20 according to an embodiment. Referring to FIG. 8, as described above, after the first layer 321 and the second layer 322 are pressed to a predetermined pressure, the second substrate 200 is removed, and it can be seen that the surface color is a color other than the black color of the second anode active material layer 222 containing a carbon-based active material. Therefore, it can be seen that a contact layer 23 having a relatively light color is formed on the second anode active material layer 222.

[0131] If, during the manufacturing process of the anode layer 20, the first layer 321 and the second layer 322 are pressed together at a predetermined pressure, for example, a pressure lower than 150 MPa, and then the second substrate 200 is removed, the anode layer 20 will simply have a structure in which the first layer 321 and the second layer 322 are bonded together, as shown in Fig. 9. As a result, it can be confirmed that the surface color of the anode layer 20 exhibits black, which is the hue of the second anode active material layer 222 containing a carbon-based active material, as shown in Fig. 10.

[0132] 11 to 13 are cross-sectional SEM images of the anode layer 20 manufactured through the above-described manufacturing method. FIG. 12 is an enlarged image of a portion of FIG. 11, and FIG. 13 is an enlarged image of a portion of FIG. 12.

[0133] 11 to 13, it can be seen that a contact layer 23 thinner than the first negative electrode active material layer 221 is formed on the second negative electrode active material layer 222 through the above-described manufacturing process.

[0134] (Production of positive electrode layer) The cathode active material and binder, which are materials constituting the cathode active material layer 12, are added to a non-polar solvent to prepare a slurry. The prepared slurry is applied to a cathode current collector 11 and dried. The resulting laminate is pressed to prepare the cathode layer 10. The pressing may be performed using, for example, a roll press, a plate press, or hydrostatic pressure, but is not limited to these methods. Any suitable pressing method is acceptable. The pressing step may be omitted. The cathode layer 10 is prepared by compacting the mixture of materials constituting the cathode active material layer 12 into a pellet form or by spreading (molding) it into a sheet form. When preparing the cathode layer 10 using such a method, the cathode current collector 11 may be omitted. Alternatively, the cathode layer 10 may be used by impregnating it with an electrolyte solution.

[0135] (Manufacturing of solid electrolyte layer) The solid electrolyte layer 30 containing an oxide-based solid electrolyte is produced, for example, by heat treating a precursor of an oxide-based solid electrolyte material.

[0136] The oxide-based solid electrolyte can also be prepared by contacting precursors in stoichiometric amounts to form a mixture and then heat-treating the mixture. The contacting can include milling, such as ball milling, or grinding. The stoichiometrically mixed precursor mixture can be subjected to a primary heat treatment in an oxidizing atmosphere to prepare a primary heat-treated product. The primary heat treatment is performed at a temperature below 1,000°C for 1 to 36 hours. The primary heat-treated product can be ground. The primary heat-treated product can be ground by either dry or wet grinding. Wet grinding can be performed by mixing the primary heat-treated product with a solvent, such as methanol, and then milling it for 0.5 to 10 hours using a ball mill. Dry grinding can also be performed by milling the primary heat-treated product without a solvent using a ball mill. The particle size of the ground primary heat-treated product can be 0.1 μm to 10 μm, or 0.1 μm to 5 μm. The crushed product of the primary heat treatment is dried, mixed with a binder solution and formed into pellets, or simply pressed under a pressure of 1 to 10 tons to form pellets.

[0137] The pellets may be subjected to a secondary heat treatment at a temperature of less than 1,000°C for 1 to 36 hours. This secondary heat treatment results in a sintered solid electrolyte layer 30. The secondary heat treatment may be performed, for example, at 550°C to 1,000°C. The secondary heat treatment time is 1 to 36 hours. To obtain a sintered product, the secondary heat treatment temperature is higher than the primary heat treatment temperature. For example, the secondary heat treatment temperature may be 10°C or higher, 20°C or higher, 30°C or higher, or 50°C or higher than the primary heat treatment temperature. The pellets may be subjected to a secondary heat treatment in an oxidizing atmosphere and a reducing atmosphere, or a combination thereof. The secondary heat treatment may be performed in a) an oxidizing atmosphere, b) a reducing atmosphere, or c) an oxidizing atmosphere and a reducing atmosphere.

[0138] The solid electrolyte layer 30 containing a sulfide-based solid electrolyte is manufactured using a solid electrolyte formed from, for example, a sulfide-based solid electrolyte material.

[0139] The sulfide-based solid electrolyte is prepared by processing the starting materials, for example, by melt quenching or mechanical milling, but this is not necessarily limited to these methods. Any method that can be used to produce a sulfide-based solid electrolyte is acceptable. For example, when using the melt quenching method, starting materials such as Li2S and P2S5 are mixed in predetermined amounts, pelletized, reacted in a vacuum at a predetermined reaction temperature, and then quenched to produce a sulfide-based solid electrolyte material. The reaction temperature for the Li2S or P2S5 mixture is, for example, about 400°C to 1,000°C, or about 800°C to 900°C. The reaction time is, for example, 0.1 to 12 hours, or 1 to 12 hours. The quenching temperature of the reaction mixture is 10°C or below, or 0°C or below, and the quenching rate is 1°C / sec to 10,000°C / sec, or 1°C / sec to 1,000°C / sec. For example, when using a mechanical milling method, a sulfide-based solid electrolyte material is produced by stirring and reacting starting materials, such as Li2S and P2S5, using a ball mill or the like. The stirring speed and stirring time of the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the production rate of the sulfide-based solid electrolyte material, and the longer the stirring time, the higher the raw material conversion rate to the sulfide-based solid electrolyte material. Next, the mixed raw materials obtained by a melt quenching method, mechanical milling method, or the like are heat-treated at a predetermined temperature and then pulverized to produce a particulate solid electrolyte. If the solid electrolyte has glass transition properties, it can be converted from amorphous to crystalline by heat treatment.

[0140] The solid electrolyte obtained by such a method is deposited using a deposition method known to those skilled in the art, such as aerosol deposition, cold spray, or sputtering, to produce the solid electrolyte layer 30. Alternatively, the solid electrolyte layer 30 can be produced by pressing solid electrolyte particles alone. Alternatively, the solid electrolyte layer 30 can be produced by mixing the solid electrolyte, a solvent, and a binder, applying the mixture, drying, and pressing the mixture.

[0141] (Manufacturing of all-solid-state secondary batteries) The anode layer 20, the cathode layer 10, and the solid electrolyte layer 30 produced by the above-described method are prepared, and the cathode layer 10 and the anode layer 20 are stacked so that the solid electrolyte layer 30 is sandwiched between them, and then pressurized to produce an all-solid-state secondary battery 1.

[0142] For example, after the contact layer 23 of the anode layer 20 is arranged to face one surface of the solid electrolyte layer 30, the anode layer 20 and the solid electrolyte layer 30 are pressed together at a predetermined pressure to bond the anode layer 20 to one surface of the solid electrolyte layer 30.

[0143] The pressing may be, for example, roll pressing, uniaxial pressing, flat pressing, warm isostatic pressing (WIP), cold isostatic pressing (CIP), etc., but is not necessarily limited to such methods, and any pressing method used in the art is acceptable. The pressure applied during pressing is, for example, 50 MPa to 750 MPa, or 100 MPa to 700 MPa. The time for applying pressure is 5 seconds to 5 minutes. The pressing is carried out, for example, at a temperature of room temperature to 90°C or lower, or at a temperature of 20 to 90°C. Alternatively, the pressing is carried out at a high temperature of 100°C or higher.

[0144] Next, the positive electrode layer 10 is placed on the other surface of the solid electrolyte layer 30 different from (e.g., opposite to) the surface on which the negative electrode layer 20 is placed, and the positive electrode layer 10 is bonded to the other surface of the solid electrolyte layer 30 by applying a predetermined pressure.

[0145] The pressing may be, for example, roll pressing, uniaxial pressing, plate pressing, warm isostatic pressing (WIP), cold isostatic pressing (CIP), etc., but is not necessarily limited to such methods, and any pressing method used in the art is acceptable. The pressure applied during pressing is, for example, 50 MPa to 750 MPa, or 100 MPa to 700 MPa. The time for applying pressure is 5 seconds to 5 minutes. The pressing is carried out, for example, at a temperature of room temperature to 90°C or less, or at a temperature of 20 to 90°C. Alternatively, the pressing is carried out at a high temperature of 100°C or higher.

[0146] The configuration and manufacturing method of the all-solid-state secondary battery 1 described above is an example of this embodiment, and the components, manufacturing procedures, etc. can be appropriately changed. The pressurization can be omitted.

[0147] The present invention will be explained in more detail through the following examples and comparative examples, but the examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention.

[0148] Comparative Example 1: Anode layer composed of a single lithium metal layer (Manufacturing of solid electrolyte layer / negative electrode layer laminate) LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 A 10 μm-thick copper (Cu) foil coated with a 20 μm-thick lithium (Li) metal was placed on one side of the LLZO pellet, and a pressure of 250 MPa was applied at 25°C by cold isostatic pressing (CIP) to prepare a solid electrolyte layer / negative electrode layer laminate.

[0149] (Positive electrode layer manufacturing) As the positive electrode active material, LiNi 0.8 Co 0.15 Mn 0.05O2 (NCM) was prepared. Polytetrafluoroethylene (Teflon (registered trademark) binder manufactured by DuPont) was prepared as a binder. Carbon nanofiber (CNF) was prepared as a conductive additive. These materials were then mixed in a mass ratio of positive electrode active material:conductive additive:binder = 100:2:1. The mixture was stretched into a sheet to prepare a positive electrode active material sheet. The positive electrode active material sheet was then pressure-bonded to a positive electrode current collector made of 18 μm-thick aluminum foil to prepare a positive electrode layer.

[0150] The prepared positive electrode active material layer of the positive electrode layer was immersed in an electrolyte solution in which 2.0M of LiFSI was dissolved in Pyr13FSI (N-propyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)imide), an ionic liquid.

[0151] (Manufacturing of all-solid-state secondary batteries) The positive electrode layer was placed in a stainless steel (SUS) cap so that the positive electrode active material layer impregnated with an ionic liquid electrolyte faced upward. The solid electrolyte layer / negative electrode layer laminate was placed on top of the positive electrode active material layer, and the cap was sealed to produce an all-solid-state secondary battery.

[0152] The positive electrode layer and the negative electrode layer were insulated by an insulator. Parts of the positive electrode current collector and the negative electrode current collector were protruded outside the sealed battery and used as positive electrode layer terminals and negative electrode layer terminals.

[0153] Comparative Example 2 (negative electrode layer composed of a lithium alloy layer and a carbon metal composite layer) (Manufacturing of solid electrolyte layer / negative electrode layer laminate) LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 ) pellets were prepared. A first negative electrode layer was prepared by coating a 10 μm-thick SUS304 foil with a 10 μm-thick carbon composite layer containing a carbon active material and silver (Ag).

[0154] The first negative electrode layer was placed facing one side of the LLZO pellet, and a pressure of 250 MPa was applied at 25°C using cold isostatic pressing (CIP) to attach the first negative electrode layer to the LLZO pellet.The SUS304 stainless steel foil was then removed, and a solid electrolyte layer / first negative electrode layer was prepared.

[0155] A second negative electrode layer, which was made of 10 μm-thick copper (Cu) foil coated with 20 μm-thick lithium (Li) metal, was placed on the solid electrolyte layer / first negative electrode layer, and a pressure of 100 MPa was applied at 25°C by cold isostatic pressing (CIP) to prepare a solid electrolyte layer / negative electrode layer laminate.

[0156] (Manufacturing of positive electrode layers and all-solid-state secondary batteries) A positive electrode layer and an all-solid-state secondary battery were manufactured in the same manner as in Comparative Example 1, except that the solid electrolyte layer / negative electrode layer stack manufactured above was used.

[0157] Example 1 (negative electrode layer composed of a lithium alloy layer, a carbon layer, and a lithium alloy layer) (Manufacturing of solid electrolyte layer / negative electrode layer laminate) Carbon black, used as a conductive material, and silver (Ag) nanoparticles, which can form an alloy with lithium, are mixed with a binder to form a slurry, which is then uniformly coated on a stainless steel foil (second substrate) and dried. This forms the precursor electrode (second layer) for the negative electrode layer. Separately, a lithium metal electrode (first layer) is prepared on a negative electrode current collector (first substrate).

[0158] The prepared precursor electrode and the lithium metal electrode are arranged to face each other, and then 250 MPa is applied at 25° C. by cold isostatic pressing (CIP) to bond the precursor electrode and the lithium metal electrode.

[0159] During this bonding process, a Li-Ag alloy layer (contact layer) is formed between the precursor electrode and the stainless steel foil, transforming the lithium metal electrode into a Li-Ag alloy layer (first negative electrode active material layer) and the precursor electrode into a carbon layer (second negative electrode active material layer) containing a carbon-based active material and lithium.

[0160] The stainless steel foil was then removed, and a negative electrode layer was prepared in which a 20 μm thick Li-Ag alloy layer, a 5.5 μm thick carbon layer, and a 0.5 μm thick Li-Ag alloy layer were sequentially stacked on the negative electrode current collector.

[0161] LLZO(Li) with a thickness of 350 μm 6.5 La3Zr 1.5 Ta 0.5 O 12 ) pellets were prepared. An anode layer was placed on one side of the LLZO pellet so that the 0.5 μm thick Li-Ag alloy layer faced it, and a pressure of 250 MPa was applied at 25°C by cold isostatic pressing (CIP) to attach the anode layer to the LLZO pellet, thereby preparing a solid electrolyte layer / anode layer laminate.

[0162] (Manufacturing of positive electrode layers and all-solid-state secondary batteries) A positive electrode layer and an all-solid-state secondary battery were manufactured in the same manner as in Comparative Example 1, except that the solid electrolyte layer / negative electrode layer stack manufactured above was used.

[0163] Evaluation example 1: Interface resistance evaluation The interface resistance of each of the full cells produced in Comparative Examples 1 and 2 and Example 1 was measured. For the full cells prepared in Comparative Examples 1 and 2 and Example 1, the impedance of the pellets was measured using an impedance analyzer (Solartron 1400A / 1455A impedance analyzer) by the two-probe method. The frequency range was 0.1 Hz to 1 MHz, and the amplitude voltage was 10 mV.

[0164] The measurements were made in an air atmosphere at 25° C. Nyquist plots relating to the impedance measurement results are shown in FIGS.

[0165] 14 and 15, in the structure (Comparative Example 2) having an anode layer in which the carbon layer is in direct contact with the solid electrolyte layer, the interface resistance was 2,000 ohm cm. 2However, in the structure having the negative electrode layer in which the lithium metal layer or the lithium alloy layer contacts the solid electrolyte layer (Comparative Example 1, Example 1), the interface resistance is shown to be less than 2,000 ohm cm2.

[0166] Evaluation example 2: Charge / discharge test The charge / discharge characteristics of the all-solid-state secondary batteries produced in Comparative Examples 1 and 2 and Example 1 were evaluated by the following charge / discharge test. In the charge / discharge test, charge / discharge was carried out at 60°C while changing the current density in order to confirm the driving characteristics of the all-solid-state secondary batteries in a high current density state.

[0167] As shown in FIG. 16, in the structure having a negative electrode layer formed of a single lithium metal layer (Comparative Example 1), the current was 1.0 mA / cm 2 As shown in FIG. 17, in the structure having the anode layer in which the carbon layer is in direct contact with the solid electrolyte layer (Comparative Example 2), the current was 0.9 mA / cm 2 A short circuit occurred.

[0168] In contrast, in the structure (Example 1) in which a thin Li-Ag alloy layer is in contact with the solid electrolyte layer, as shown in FIG. 18, the current was 1.8 mA / cm 2 Stable operation was possible without short-circuiting until

[0169] From these results, it can be concluded that in a structure in which the anode layer has a multilayer structure but a thin metal layer is in contact with the solid electrolyte layer, the volume change that occurs during charge and discharge can be alleviated, local concentration of current at high current density is reduced, and short-circuiting of the all-solid-state secondary battery is prevented.

[0170] To aid in understanding the present invention, exemplary embodiments of an all-solid-state secondary battery and a method for manufacturing the same have been described and illustrated in the accompanying drawings. However, it should be understood that such embodiments are merely for the purpose of illustrating the present invention and are not intended to limit the present invention. It should be understood that the present invention is not limited to the illustrated and described embodiments, as various other modifications may be made by those skilled in the art. [Explanation of symbols]

[0171] 1 All-solid-state secondary battery 10 Positive electrode layer 11 Positive electrode current collector 12 Cathode active material layer 20 negative electrode layer 21 Negative electrode current collector 22 Negative electrode active material layer 23 Contact layer 30 Solid electrolyte layer 100 First substrate 200 Second board 221 First negative electrode active material layer 222 Second negative electrode active material layer 321 1st layer 322 2nd layer

Claims

1. An all-solid-state secondary battery including a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode, The negative electrode is a negative electrode current collector; a first negative electrode active material layer in contact with the negative electrode current collector and containing a first metal; a second negative electrode active material layer disposed between the first negative electrode active material layer and the solid electrolyte layer and including a carbon-based active material; a contact layer disposed between the second negative electrode active material layer and the solid electrolyte layer so as to prevent contact between the second negative electrode active material layer and the solid electrolyte layer, the contact layer includes a second metal and has a thickness smaller than a thickness of the first negative electrode active material layer; the thickness of the first negative electrode active material layer is 10 μm or more; the thickness of the contact layer is between 1 nm and 1 μm; the first metal comprises lithium metal or a lithium alloy; The all-solid-state secondary battery, wherein the second metal includes lithium metal or a lithium alloy.

2. The all-solid-state secondary battery according to claim 1 , wherein the first metal and the second metal are the same.

3. 2. The all-solid-state secondary battery according to claim 1, wherein the thickness of the contact layer is 20% or less of the thickness of the first negative electrode active material layer.

4. The all-solid-state secondary battery according to claim 1 , wherein the contact layer has a thickness smaller than a thickness of the second negative electrode active material layer.

5. The all-solid-state secondary battery according to claim 1 , wherein the contact layer does not contain a carbon-based material.

6. The all-solid-state secondary battery according to claim 1 , wherein a volume change rate of the first negative electrode active material layer is greater than a volume change rate of the contact layer during charge / discharge cycles.

7. The all-solid-state secondary battery according to claim 1 , wherein a volume change rate of the second negative electrode active material layer is greater than a volume change rate of the contact layer during charge / discharge cycles.

8. 2. The all-solid-state secondary battery according to claim 1, wherein the volume of the contact layer in a charged state is 1.5 to 20 times the volume of the contact layer in a discharged state.

9. 2. The all-solid-state secondary battery according to claim 1, wherein the volume of the first negative electrode active material layer in a charged state is 1.5 to 500 times the volume of the first negative electrode active material layer in a discharged state.

10. the volume of the second negative electrode active material layer in a charged state is larger than the volume of the second negative electrode active material layer in a discharged state, 2 . The all-solid-state secondary battery according to claim 1 , wherein a volume of the second negative electrode active material layer in a charged state is equal to or less than twice a volume of the second negative electrode active material layer in a discharged state.

11. The all-solid-state secondary battery according to claim 1 , wherein the solid electrolyte layer contains an oxide-based solid electrolyte.

12. providing a positive electrode layer; providing a negative electrode layer; providing a solid electrolyte layer; bonding a negative electrode layer to one surface of the solid electrolyte layer; and bonding a positive electrode layer to the other surface of the solid electrolyte layer, The step of providing the negative electrode layer comprises: disposing a first layer including lithium metal or a lithium alloy disposed on a first substrate and a second layer including a carbon-based active material disposed on a second substrate; disposing the first layer and the second layer so that they face each other, and applying a pressure equal to or greater than a predetermined pressure so that the first substrate and the second substrate become closer to each other; In the process of pressing the first substrate and the second substrate together, a third layer containing lithium metal or a lithium alloy is formed between the second substrate and the second layer, the third layer having a thickness thinner than that of the first layer, the first layer having a thickness of 10 μm or more, and the third layer having a thickness of 1 nm to 1 μm; the step of bonding the anode layer to one surface of the solid electrolyte layer is performed such that the third layer is disposed between the second layer and the solid electrolyte layer.

13. the second layer includes a metal capable of alloying with lithium; In the step of pressing the first substrate and the second substrate together, The method for producing an all-solid-state secondary battery according to claim 12 , wherein the metal capable of forming an alloy with lithium in the first layer and the third layer forms an alloy with lithium.

14. In the step of providing the negative electrode layer, The method for manufacturing an all-solid-state secondary battery according to claim 12 , further comprising removing the second substrate after the third layer is formed.

15. 13. The method of claim 12, wherein the pressure applied in the step of pressing the first substrate and the second substrate together is 150 MPa to 1,000 MPa.

16. providing a first layer comprising lithium metal or a lithium alloy disposed on a first substrate and a second layer comprising a carbon-based active material disposed on a second substrate; disposing the first layer and the second layer so that they face each other, and applying a pressure equal to or greater than a predetermined pressure so that the first substrate and the second substrate become closer to each other; In the step of pressing the first substrate and the second substrate together, a third layer containing lithium metal or a lithium alloy is formed between the second substrate and the second layer, the third layer having a thickness thinner than that of the first layer, the first layer having a thickness of 10 μm or more, and the third layer having a thickness of 1 nm to 1 μm, The all-solid-state secondary battery includes the third layer between the second layer and the solid electrolyte layer.

17. the second layer includes a metal capable of alloying with lithium; In the step of pressing the first substrate and the second substrate together, 17. The method for manufacturing a negative electrode layer of an all-solid-state secondary battery according to claim 16, wherein in the first layer and the third layer, the metal capable of forming an alloy with lithium forms an alloy with lithium.

18. the method further comprising removing the second substrate after the third layer is formed; 17. The method of claim 16, wherein the pressure applied in the step of pressing the first substrate and the second substrate together is 150 MPa to 1,000 MPa.

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