Argyrodite-type sulfide-based solid electrolyte, solid electrolyte membrane, and all-solid-state rechargeable batteries

Abstract

The present invention relates to an argyrodite-type sulfide-based solid electrolyte represented by chemical formula 1, a solid electrolyte membrane comprising same, and an all-solid rechargeable battery. [chemical formula 1] (LiaM1 bM2 c)(PdM3 e)(SfX1 g)X2 h In chemical formula 1, 4≤a≤8; M1 is at least one element selected from Groups 2 to 11 of the periodic table, 0<b<0.5; M2 is at least one element other than Li, selected from Group 1 of the periodic table, 0≤c<0.5; M3 is Bi, Cu, Ge, Sb, Si, Sn, Zn, or a combination thereof, 0<d<1, 0<e<1; X1 is O, N, SOn, or a combination thereof, 1.5≤n≤5, 3≤f≤7, 0≤g<2; and X2 is at least one element selected from Group 17 of the periodic table, 0<h≤2.

Description

Argyrodite-type sulfide-based solid electrolyte, solid electrolyte membrane, and all-solid-state secondary battery

[0001] It relates to an argyrodite-type sulfide-based solid electrolyte, a solid electrolyte membrane, and an all-solid-state secondary battery.

[0002] Lithium secondary batteries, which boast high energy density and portability, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research is underway to utilize high-energy-density lithium secondary batteries as power sources for hybrid and electric vehicles, or as power storage devices.

[0003] Commercially available lithium secondary batteries use electrolytes containing flammable organic solvents, posing safety concerns that can lead to explosions or fires in the event of collisions, penetrations, or other problems. Therefore, semi-solid or all-solid-state batteries, which avoid the use of electrolytes, are being proposed. All-solid-state batteries are comprised entirely of solid materials, specifically those that utilize solid electrolytes. These all-solid-state batteries are safe, eliminating the risk of electrolyte leakage and explosion, and offer the advantage of being easy to manufacture in thin forms.

[0004] Sulfide-based solid electrolytes with high ionic conductivity are mainly used as solid electrolytes. Among them, argyrodite-type sulfide-based solid electrolytes have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It can exhibit high ionic conductivity approaching the S / cm range, and has the advantage of having soft mechanical properties, which can form close bonds between solid electrolytes and between the solid electrolyte and the positive active material. Accordingly, all-solid-state secondary batteries using argyrodite-type sulfide-based solid electrolytes can exhibit improved rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0005] Provided is an argyrodite-type sulfide-based solid electrolyte exhibiting high lithium ion conductivity, suppressing chemical side reactions in air, and improving moisture stability.

[0006] In one embodiment, an argyrodite-type sulfide-based solid electrolyte represented by chemical formula 1 is provided.

[0007] [Chemical Formula 1]

[0008] (Li a M 1 b M 2 c )(P d M 3 e )(S f X 1 g )X 2 h

[0009] In the above chemical formula 1, 4≤a≤8, and M 1 is at least one element selected from groups 2 and 11 of the periodic table, and 0 <b<0.5이고, M 2 is at least one element other than Li selected from group 1 of the periodic table, and 0≤c<0.5, and M 3 is Bi, Cu, Ge, Sb, Si, Sn, Zn or a combination thereof and 0 <d<1, 0<e<1이고, X 1 is O, N, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤7, 0≤g<2, and X 2 is at least one element selected from group 17 of the periodic table, and 0 <h≤2이다.

[0010] In another embodiment, a solid electrolyte membrane is provided that includes an argyrodite-type sulfide-based solid electrolyte represented by the above chemical formula 1.

[0011] In another embodiment, an all-solid-state secondary battery is provided, which includes a positive electrode, a negative electrode, and a solid electrolyte membrane positioned between the positive electrode and the negative electrode, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte membrane includes an argyrodite-type sulfide-based solid electrolyte represented by the chemical formula 1.

[0012] In another embodiment, an all-solid-state secondary battery is provided, comprising a positive electrode, a negative electrode, and a solid electrolyte membrane positioned between the positive electrode and the negative electrode and comprising an argyrodite-type sulfide-based solid electrolyte represented by the chemical formula 1.

[0013] According to one embodiment, an argyrodite-type sulfide-based solid electrolyte can exhibit high ionic conductivity while suppressing chemical side reactions in air and exhibiting excellent moisture stability. A solid electrolyte membrane and all-solid-state secondary battery containing the same can exhibit excellent rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0014] Figures 1 and 2 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0015] Figure 3 is an X-ray diffraction (XRD) graph for the solid electrolytes of Comparative Example 1 and Examples 1 to 4.

[0016] Figure 4 is an XRD graph for the solid electrolytes of Comparative Example 1 and Examples 5 to 8.

[0017] Figure 5 is a graph showing the ionic conductivity retention rate of the solid electrolytes of Comparative Example 1 and Examples 1, 3, 5, and 6 after being left in a dry room with a dew point of -45°C or lower for 3 days compared to immediately after synthesis.

[0018] Below, specific implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

[0019] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0020] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0021] It should be understood that the terms "include," "comprise," or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0022] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there are other elements in between. Conversely, when an element is said to be "directly over" another element, it means that there are no other elements in between.

[0023] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0024] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope image or a scanning electron microscope image. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size can mean the diameter (D50) of particles in a particle size distribution that have a cumulative volume of 50% by volume. In addition, unless otherwise defined, the average particle size can be obtained by randomly measuring the sizes (diameters or major axis lengths) of about 20 particles in a scanning electron microscope image to obtain a particle size distribution, and taking the diameter (D50) of particles in the particle size distribution that have a cumulative volume of 50% by volume as the average particle size.

[0025] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0026] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0027] solid electrolyte

[0028] In one embodiment, an argyrodite-type sulfide-based solid electrolyte represented by chemical formula 1 is provided.

[0029] [Chemical Formula 1]

[0030] (Li a M 1 b M 2 c )(P d M 3 e )(S f X 1 g )X 2 h

[0031] In the above chemical formula 1, 4≤a≤8, and M 1is at least one element selected from groups 2 and 11 of the periodic table, and 0 <b<0.5이고, M 2 is at least one element other than Li selected from group 1 of the periodic table, and 0≤c<0.5, and M 3 is Bi, Cu, Ge, Sb, Si, Sn, Zn or a combination thereof and 0 <d<1, 0<e<1이고, X 1 is O, N, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤7, 0≤g<2, and X 2 is at least one element selected from group 17 of the periodic table, and 0 <h≤2이다.

[0032] The argyrodite-type sulfide-based solid electrolyte represented by the above chemical formula 1 can achieve a high lithium ion conductivity of 2.0 mS / cm or more at 25°C, and at the same time, can exhibit high stability against moisture. For example, the solid electrolyte can have an ionic conductivity retention rate of 67% or more, which is the ratio of the ionic conductivity immediately after synthesis to the ionic conductivity after being stored in a dry room having a dew point of -45°C or lower for 3 days.

[0033] An argyrodite-type sulfide-based solid electrolyte according to one embodiment may, for example, have some of the Li sites replaced by M 1 Replace with and optionally M 2 and at the same time replace some of the P positions with M 3 Doping with , and optionally some of the S sites are X 1 It can be said that the composition is substituted with . This solid electrolyte can implement high lithium ion conductivity and improve moisture stability compared to the existing argyrodite-type sulfide-based solid electrolyte.

[0034] A solid electrolyte according to one embodiment has a crystal structure in which some of the lithium sites are M 1 As a substitute for M, lithium ion conductivity can be improved and activation energy can be reduced. 1For example, it can be a metallic element with an oxidation number of +1 or +2, and can be said to be an element having an ionic radius larger than a lithium ion. For example, if another element having the same oxidation number as lithium but a larger ionic radius than the lithium ion is placed in some of the lithium sites in Chemical Formula 1, the volume of the crystal lattice can increase, and thus the movement of lithium ions can be more soluble within the crystal lattice. As another example, if an element having a larger oxidation number than lithium is placed in some of the lithium sites in Chemical Formula 1, some of the lithium sites can become vacant sites, and thus the movement of lithium ions can be more easily achieved within the crystal lattice.

[0035] M 1 For example, it may be Mg, Ca, Cu, Ag, or a combination thereof, and for example, it may be Mg, Cu, Ag, or a combination thereof.

[0036] In chemical formula 1, b is M 1 It means the molar ratio of elements and is 0 <b<0.5의 범위이고, 예를 들어 0.001≤b<0.5, 0.001≤b≤0.4, 0.001≤b≤0.3, 0.001≤b≤0.2, 0.001≤b≤0.1, 0.001≤b≤0.05, 또는 0.01≤b≤0.05일 수 있다. 화학식 1에서 b가 상기 범위를 만족하는 경우 아지로다이트형 황화물계 고체 전해질의 리튬 이온 전도도가 더욱 향상될 수 있다.

[0037] In chemical formula 1, b / (a+b+c) is M at the lithium site. 1 This may mean a substituted ratio, for example, 0.001≤b / (a+b+c)≤0.05, 0.001≤b / (a+b+c)≤0.04, 0.001≤b / (a+b+c)≤0.03, 0.001≤b / (a+b+c)≤0.02, or 0.001≤b / (a+b+c)≤0.01. M 1When the substitution ratio satisfies the above range, the lithium ion conductivity of the argyrodite-type sulfide-based solid electrolyte can be further improved.

[0038] The compound of formula 1 has a crystal structure in which some of the lithium sites are selectively M 2 can be replaced with M 2 is an element in group 1 of the periodic table excluding Li, which may be Na, K, Rb, Cs, Fr, or a combination thereof, for example, Na, K, or a combination thereof. M 2 It can be said that it is an element with an oxidation number of +1 and a larger radius than the lithium ion. In chemical formula 1, if another element with the same oxidation number as lithium but a larger ionic radius than the lithium ion is placed in some of the lithium sites, the volume of the crystal lattice can increase, and thus the movement of lithium ions within the crystal lattice can be more soluble.

[0039] In chemical formula 1, c is M 2 It refers to the molar ratio of elements and is in the range of 0≤c<0.5, for example, 0≤c≤0.4, 0≤c≤0.3, 0≤c≤0.2, or 0 <c≤0.15일 수 있다.

[0040] In chemical formula 1, a represents the molar ratio of Li, and is in the range of 4≤a≤8, and may be, for example, 4≤a≤7, or 5≤a≤6.

[0041] An argyrodite-type sulfide-based solid electrolyte according to an embodiment of the present invention has a crystal structure in which some of the P sites are M 3 It is characterized by being replaced by M 3 PS4 in the argyrodite crystal structure by doping some of the P sites with at least one element selected from Bi, Cu, Ge, Sb, Si, Sn, and Zn. 3- The structural stability of the solid electrolyte can be improved and the reactivity with moisture of the solid electrolyte can be reduced. M 3 For example, it can be Cu, Si, Sn, Zn, or a combination thereof.

[0042] Meanwhile, Cu element is present in the Li site (M 1 ) is substituted, or P place (M 3 ) can be substituted in the Li site and the P site, or can be substituted simultaneously in the Li site and the P site. It is understood that the state in which the oxidation number of Cu is 1 is substituted in the Li site and the state in which the oxidation number of Cu is 2 is substituted in the P site, but is not limited thereto. When the Cu element is doped into the argyrodite crystal structure, the crystal structure can be further stabilized and ionic conductivity can be improved.

[0043] In chemical formula 1, 0.9≤d+e≤1.1 may be true, and for example, d+e=1.

[0044] In Chemical Formula 1, the molar ratio of P, d, may be, for example, 0.7≤d≤0.99, 0.8≤d≤0.99, 0.9≤d≤0.99, or 0.95≤d≤0.99. In Chemical Formula 1, M 3 The molar ratio e may be, for example, 0.01≤e≤0.3, 0.01≤e≤0.2, 0.01≤e≤0.1, or 0.01≤e≤0.05.

[0045] Also in P position M 3 The substitution ratio e / (d+e) can be, for example, 0.01≤e / (d+e)≤0.3, 0.01≤e / (d+e)≤0.2, 0.01≤e / (d+e)≤0.1, or 0.01≤e / (d+e)≤0.5. M 3 When the substitution ratio satisfies the above range, the argyrodite crystal structure can be further stabilized and moisture stability can be improved.

[0046] In chemical formula 1, f may mean the molar ratio of S and satisfies 3≤f≤7, and may be, for example, 3≤f≤6, 3≤f≤5, or 4≤f≤5.

[0047] An argyrodite-type sulfide-based solid electrolyte according to an embodiment of the present invention selectively comprises a portion of S sites being X 1 can be replaced with X 1Silver O, N, and SO n There may be at least one selected from among, for example O, SO n , or a combination thereof. Part of the S digit may be X 1 When substituted with , the argyrodite crystal structure can be further stabilized, ionic conductivity can be further improved, and moisture stability can be enhanced.

[0048] In one implementation, some of the Li positions are M 1 is replaced by and part of the P position is M 3 As it is replaced by X, part of the S position is replaced by X. 1 When substituted, these solid electrolytes can have improved moisture stability while realizing high ionic conductivity.

[0049] In chemical formula 1, g is X 1 The molar ratio may be 0≤g<2, 0.001≤g≤1.5, 0.01≤g≤1.0, 0.01≤g≤0.9, 0.01≤g≤0.8, 0.01≤g≤0.7, 0.01≤g≤0.6, 0.01≤g≤0.5, 0.01≤g≤0.4, 0.01≤g≤0.3, 0.01≤g≤0.2, 0.01≤g≤0.1, or 0.01≤g≤0.05.

[0050] X at the S position in chemical formula 1 1 g / (f+g), which represents the substitution ratio, may be, for example, 0.01≤g / (f+g)≤0.3, or, for example, 0.01≤g / (f+g)≤0.2, 0.01≤g / (f+g)≤0.1, or 0.01≤g / (f+g)≤0.05. X 1 When the substitution ratio satisfies the above range, the solid electrolyte can exhibit high lithium ion conductivity while improving moisture stability.

[0051] X in chemical formula 1 2 is a halogen element in group 17 of the periodic table, which can be F, Cl, Br, I, or a combination thereof, for example, Cl, Br, or a combination thereof. In chemical formula 1, h is X2 It represents the molar ratio and is in the range of 0≤h≤2, for example, 0 <h≤2, 0.5≤h≤2, 또는 1≤h≤2일 수 있다.

[0052] The above chemical formula 1 can be represented, for example, by the chemical formula 2 below.

[0053] [Chemical Formula 2]

[0054] (Li a Cu b )(P d M 3 e )(S f X 1 g )X 2 h

[0055] In the above chemical formula 2, 4≤a≤8, and 0 <b<0.5이고, M 3 is Bi, Cu, Ge, Sb, Si, Sn, Zn or a combination thereof and 0 <d<1, 0<e<1이고, X 1 is O, N, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤7, 0≤g<2, and X 2 is at least one element selected from group 17 of the periodic table, and 0 <h≤2이다.

[0056] The argyrodite-type sulfide-based solid electrolyte represented by the above chemical formula 2 can exhibit very high ionic conductivity while simultaneously exhibiting high moisture stability.

[0057] In chemical formula 2, 4≤a≤7, or 5≤a≤6, 0.001≤b<0.5, 0.001≤b≤0.4, 0.001≤b≤0.3, 0.001≤b≤0.2, 0.001≤b≤0.1, 0.001≤b≤0.05, or 0.01≤b≤0.05, 0.7≤d≤0.99, 0.8≤d≤0.99, 0.9≤d≤0.99, or 0.95≤d≤0.99, 0.9≤d+e≤1.1, and for example, d+e=1. Also, in Chemical Formula 2, 0.01≤e≤0.3, 0.01≤e≤0.2, 0.01≤e≤0.1, or 0.01≤e≤0.05, 3≤f≤6, 3≤f≤5, or 4≤f≤5, 0.001≤g≤1.5, 0.01≤g≤1.0, 0.01≤g≤0.9, 0.01≤g≤0.8, 0.01≤g≤0.7, 0.01≤g≤0.6, 0.01≤g≤0.5, 0.01≤g≤0.4, 0.01≤g≤0.3, 0.01≤g≤0.2, 0.01≤g≤0.1, or 0.01≤g≤0.05, 0 <h≤2, 0.5≤h≤2, 또는 1≤h≤2일 수 있다.

[0058] The argyrodite-type sulfide-based solid electrolyte represented by chemical formula 1 according to one embodiment may be represented by, for example, chemical formulas listed in Table 1 below, but is not limited thereto.

[0059] (1)Li 5.765 Cu 0.03 P 0.985 Zn 0.015 S 4.75 Cl 1.25 (2)Li 5.81 Cu 0.03 P 0.97 Zn 0.03 S 4.75 Cl 1.25 (3)Li 5.73 Cu 0.03 P 0.99 Sn 0.01 S 4.75 Cl 1.25 (4)Li 5.75 Cu 0.03 P 0.97 Sn 0.03 S4.75 Cl 1.25 (5)Li 5.735 I will 0.03 P 0.985 Yes 0.015 WITH 4.75 Cl 1.25 (6)Li 5.75 I will 0.03 P 0.97 Yes 0.03 WITH 4.75 Cl 1.25 (7)Li 5.82 I will 0.03 P 0.9 Yes 0.1 WITH 4.75 Cl 1.25 (8)Li 5.92 I will 0.03 P 0.8 Yes 0.2 WITH 4.75 Cl 1.25 (9)Li 5.735 I will 0.03 P 0.985 Sn 0.015 WITH 4.725 (SO4) 0.025 Cl 1.25 (10)Li 5.75 I will 0.03 P 0.97 Yes 0.03 WITH 4.725 (SO4) 0.025 Cl 1.25 (11)Li 6.02 I will 0.03 P 0.7 Sn 0.3 WITH 4.75 No. 1.25 (12)Li 6.02 I will 0.03 P 0.7 Sn 0.3 WITH 4.75 AND 1.25

[0060] According to one embodiment, a solid electrolyte may have an ionic conductivity of 1.0 mS / cm or more at 25°C, for example, 2.0 mS / cm or more, for example, 2.0 mS / cm to 10 mS / cm, or 2.0 mS / cm to 6 mS / cm. A solid electrolyte membrane or all-solid-state secondary battery using such a solid electrolyte may have easy ion transport, thereby reducing internal resistance and improving output characteristics, rate characteristics, etc.

[0061] A solid electrolyte according to one embodiment is characterized by high stability against moisture, and for example, the solid electrolyte may have an ionic conductivity retention rate, which is a ratio of the ionic conductivity immediately after synthesis to the ionic conductivity after being left in a dry room having a dew point of -45°C or lower for 3 days, of 67% or more, and for example, 68% or more, 69% or more, or 85% or more.

[0062] The above argyrodite-type sulfide-based solid electrolyte belongs to the cubic crystal system and may belong to, for example, the F-43m space group.

[0063] The above argyrodite-type sulfide-based solid electrolyte may be in the form of particles, and its average particle diameter (D 50 ) may be, for example, 0.1 ㎛ to 5.0 ㎛ or 0.1 ㎛ to 3.0 ㎛, small particles of 0.1 ㎛ to 1.9 ㎛, or large particles of 2.0 ㎛ to 5.0 ㎛. The solid electrolyte may be a mixture of small particles having an average particle diameter of 0.1 ㎛ to 1.9 ㎛ and large particles having an average particle diameter of 2.0 ㎛ to 5.0 ㎛. Here, the average particle diameter may be measured by an electron microscope image, and for example, a particle size distribution is obtained by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image, and here, D 50 It may have been calculated.

[0064] Method for producing an argyrodite-type sulfide-based solid electrolyte

[0065] According to one embodiment, an argyrodite-type sulfide-based solid electrolyte may include, for example, lithium sulfide, phosphorus sulfide, M 1 Raw material, M 3 Mix raw materials and lithium halides and optionally M 2 Raw materials or X 1 It can be manufactured by mixing raw materials.

[0066] M 1 The raw material is M 1 It may be a sulfide containing an element, such as MgS, CaS, CuS, Cu2S, AgS, etc. M 2 The raw material is M 2 It may be a sulfide containing elements, such as Na2S, K2S, etc. M 3 The raw material is M 3 It may be a sulfide containing the element, and may be Bi2S3, CuS, GeS2, Sb2S3, SiS2, SnS2, ZnS, etc. X 1 The raw materials may be lithium oxide, lithium nitride, lithium nitrous oxide, phosphorus oxide such as P2O5, etc.

[0067] The above raw materials can be mixed in stoichiometric proportions to produce the compound of the aforementioned chemical formula 1. Mechanical milling or a solution method can be used as a method for mixing the raw materials. Mechanical milling involves placing the starting raw materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution method, the starting raw materials can be mixed in a solvent to obtain a solid electrolyte as a precipitate.

[0068] Heat treatment may be performed after mixing the raw materials, in which case the crystals of the solid electrolyte can become more solid and ionic conductivity can be improved. The heat treatment can be performed at a temperature ranging from 400°C to 600°C, for example, from 450°C to 500°C, or from 460°C to 490°C, and for 5 to 30 hours, 10 to 24 hours, or 15 to 20 hours. Heat treatment under the above conditions can maximize ionic conductivity.

[0069] For example, the above raw materials can be mixed and heat-treated twice or more to manufacture, in which case a sulfide-based solid electrolyte with high ionic conductivity and strength can be manufactured. Manufacturing the argyrodite-type sulfide-based solid electrolyte can include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the result of the first heat treatment again and calcining at 350°C to 800°C. The first heat treatment and the second heat treatment can each be performed in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 hour to 10 hours, and the second heat treatment can be performed for 5 hours to 20 hours. The first heat treatment can have the effect of milling small raw materials, and the second heat treatment can synthesize the final solid electrolyte. Through two or more heat treatments as described above, a high-performance, robust, and argyrodite-type sulfide-based solid electrolyte with high ionic conductivity can be obtained, and such a solid electrolyte can be said to be suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C, or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C, or 400°C to 600°C.

[0070] After the heat treatment, a cooling step can be further performed, and the cooling rate can be 0.5°C / min to 3°C / min, for example 0.5°C / min to 1.5°C / min. By adjusting the cooling rate within the above range, the ionic conductivity can be maximized.

[0071] solid electrolyte membrane

[0072] In one embodiment, a solid electrolyte membrane is provided that includes an argyrodite-type sulfide-based solid electrolyte represented by the aforementioned chemical formula 1. The argyrodite-type sulfide-based solid electrolyte represented by the chemical formula 1 may be included in an amount of 70 wt% to 100 wt%, for example, 80 wt% to 99.5 wt%, 90 wt% to 99 wt%, or 95 wt% to 98 wt%, based on 100 wt% of the solid electrolyte membrane.

[0073] The thickness of the solid electrolyte film may be about 100 μm to 1000 μm, for example, 100 μm to 900 μm, 100 μm to 800 μm, 100 μm to 500 μm, or 200 μm to 400 μm.

[0074] In addition to the argyrodite-type sulfide-based solid electrolyte of the aforementioned chemical formula 1, the solid electrolyte membrane may further include a sulfide-based solid electrolyte of a different composition, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

[0075] Other sulfide-based solid electrolytes

[0076] In general, sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5--LiX (where X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0077] A sulfide-based solid electrolyte can be obtained, for example, by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20, and optionally heat-treating them. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. The ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0078] Oxide-based solid electrolyte

[0079] Oxide-based solid electrolytes include, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), 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 yO3(PLZT)(0≤x<1, 0≤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, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or mixtures thereof.

[0080] Halide-based solid electrolyte

[0081] The solid electrolyte membrane may further include, for example, a halide-based solid electrolyte. The halide-based solid electrolyte contains a halogen element as a main component, and may mean that the ratio of the halide element to all elements constituting the solid electrolyte is 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. For example, the halide-based solid electrolyte may not contain a sulfur element.

[0082] The halide-based solid electrolyte may contain lithium element, a metal element other than lithium, and a halogen element. The metal element other than lithium may be Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof. The halogen element may be F, Cl, Br, I, or a combination thereof, and may be Cl, Br, or a combination thereof. The halide-based solid electrolyte may contain, for example, Li a M1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte may be, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6 Cl6, or combinations thereof, but is not limited thereto.

[0083] bookbinder

[0084] The solid electrolyte membrane may further include a binder. Binders include, for example, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, natural rubber, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, polyurethane, and the like. copolymers, or combinations thereof.

[0085] The binder may be included in an amount of 0.1 wt% to 3 wt% based on 100 wt% of the solid electrolyte membrane, for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. When the binder is included in the above range, the components within the solid electrolyte membrane can be well combined without lowering the ionic conductivity of the solid electrolyte, thereby improving the durability and reliability of the battery.

[0086] Other ingredients

[0087] The solid electrolyte membrane may optionally further comprise an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0088] The above alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt may improve ion conductivity by enhancing the lithium ion mobility of the solid electrolyte layer.

[0089] The lithium salt may be applied without limitation on type, and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0090] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0091] Ionic liquids are salts or molten salts that are composed only of ions and are liquid at room temperature, with a melting point below room temperature.

[0092] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, trizolium, and mixtures thereof, and b) 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 - It may be a compound containing one or more anions selected from among.

[0093] The ionic liquid may be at least one selected from the group consisting of, for example, 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.

[0094] In the solid electrolyte membrane, the weight ratio of the solid electrolyte to the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0095] All-solid-state secondary battery

[0096] In one embodiment, an all-solid-state secondary battery is provided, which includes a positive electrode, a negative electrode, and a solid electrolyte membrane positioned between the positive electrode and the negative electrode. At least one of the positive electrode, the negative electrode, and the solid electrolyte membrane is characterized in that it includes an argyrodite-type sulfide-based solid electrolyte represented by the aforementioned chemical formula 1. For example, in the all-solid-state secondary battery, the positive electrode and / or the solid electrolyte membrane may include the aforementioned argyrodite-type sulfide-based solid electrolyte.

[0097] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to FIG. 1, the all-solid-state secondary battery (100) may have a structure in which a cell structure in which a negative electrode (400) including a negative electrode current collector (401) and a negative electrode active material layer (403), a solid electrolyte membrane (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode current collector (201) are laminated is housed in a battery case. The cell structure may also be a bi-cell structure in which a positive electrode / solid electrolyte membrane / negative electrode / solid electrolyte membrane / positive electrode are laminated in that order. Although FIG. 1 illustrates an assembly in which two cell structures including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200) are laminated, three or more may be laminated, for example, 2 to 200, 3 to 100, 4 to 50, etc. may be laminated.

[0098] The all-solid-state secondary battery (100) may further include an elastic sheet (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). That is, the elastic sheet (500) may be positioned between the cell structures and / or at the outermost surface of the cell structures.

[0099] anode

[0100] In one embodiment, the device comprises a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and optionally may comprise a solid electrolyte, a binder, and / or a conductive material.

[0101] positive electrode active material

[0102] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0103] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, lithium-rich layered oxide, or a combination thereof.

[0104] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more based on 100 mol% of metals excluding lithium in a lithium transition metal composite oxide. The nickel content in the high-nickel cathode active material may be 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and 99 mol% or less based on 100 mol% of metals excluding lithium. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0105] As a more specific example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤0.5, 0 < α < 2);Li a Ni 1-b-c Mn b X c O 2-α D α(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2);Li a Ni b Co c L 1 d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1);; Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(0.90 ≤ a ≤1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); Li a FePO4(0.90 ≤ a ≤ 1.8)

[0106] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X 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; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0107] The cathode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 11, a lithium cobalt-based oxide represented by the following chemical formula 12, a lithium iron phosphate-based compound represented by the following chemical formula 13, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 14, or a combination thereof.

[0108] [Chemical Formula 11]

[0109] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0110] In the above chemical formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0111] In the above chemical formula 1, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0112] [Chemical Formula 12]

[0113] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0114] In the above chemical formula 12, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M 3is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0115] [Chemical Formula 13]

[0116] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0117] In the above chemical formula 13, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0118] [Chemical Formula 14]

[0119] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0120] In the above chemical formula 14, 0.9≤a2≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0121] The average particle diameter (D) of the above positive electrode active material 50 ) may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. For example, the positive electrode active material may have an average particle diameter (D 50 ) with small particles of 1 ㎛ to 9 ㎛ and an average particle diameter (D 50 ) may include particles having a particle size range of 10 ㎛ to 25 ㎛. The positive electrode active material having such a particle size range can be harmoniously mixed with other components in the positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle size is obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle sizes (diameter, or major axis, or major axis length), and then obtaining a particle size distribution, and in the particle size distribution, the diameter (D) of the particles having a cumulative volume of 50% by volume 50 ) may be taken as the average particle diameter.

[0122] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0123] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0124] The positive electrode active material may be included in an amount of 55 wt% to 99.5 wt% based on 100 wt% of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0125] bookbinder

[0126] The binder helps the positive electrode active material particles adhere well to each other and also helps the positive electrode active material adhere well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0127] Challenge

[0128] Conductive materials are used to impart conductivity to electrodes, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0129] The content of the binder and the conductive agent may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0130] The positive electrode active material layer may optionally further include a solid electrolyte. The solid electrolyte may be an argyrodite-type sulfide-based solid electrolyte represented by the aforementioned chemical formula 1, and may also include a sulfide-based solid electrolyte of a different composition, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

[0131] For 100 wt% of the positive electrode active material layer, the solid electrolyte may be included in an amount of 0.1 wt% to 35 wt%, for example, 1 wt% to 35 wt%, 5 wt% to 30 wt%, 8 wt% to 25 wt%, or 10 wt% to 20 wt%.

[0132] In the positive electrode active material layer, the positive electrode active material may be comprised in an amount of 65 to 99 wt% and the solid electrolyte in an amount of 1 to 35 wt%, based on 100 wt% of the total of the positive electrode active material and the solid electrolyte, for example, the positive electrode active material may be comprised in an amount of 80 to 90 wt% and the solid electrolyte in an amount of 10 to 20 wt%. When the solid electrolyte is comprised in the positive electrode in such an amount, the efficiency and life characteristics of the all-solid-state secondary battery can be improved without reducing the capacity.

[0133] Al, SUS, etc. can be used as the positive electrode collector, but are not limited thereto.

[0134] cathode

[0135] An anode for an all-solid-state secondary battery may include a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0136] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0137] Materials capable of reversibly intercalating / deintercalating lithium ions include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite, such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0138] As an alloy of lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0139] As a material that can be doped and dedoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material is silicon, silicon-carbon composite, SiOx(0 <x<2), Si-Q 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소(Si를 제외함), 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합에서 선택됨), 또는 이들의 조합일 수 있다. Sn계 음극 활물질로는 Sn, SnO2, Sn계 합금 또는 이들의 조합일 수 있다.

[0140] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the composite may include secondary particles (cores) in which silicon primary particles are assembled, and an amorphous carbon coating layer (shell) positioned on the surface of the secondary particles. The amorphous carbon may also be positioned between the silicon primary particles, such that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0141] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0142] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used in combination with the carbon-based negative electrode active material.

[0143] The content of the negative active material in the negative active material layer may be 95 wt% to 99 wt% based on the total weight of the negative active material layer. For example, the negative active material layer may include 90 wt% to 99 wt% of the negative active material, 0.5 wt% to 5 wt% of the binder, and 0 wt% to 5 wt% of the conductive material.

[0144] The binder serves to adhere the negative active material particles well to each other and also to adhere the negative active material well to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0145] Non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0146] The aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0147] When using an aqueous binder as the cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li.

[0148] The dry binder is a polymeric material capable of being fiberized, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0149] Conductive materials are used to impart conductivity to electrodes, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, and silver in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0150] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0151] As another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode. The precipitation-type negative electrode may refer to a negative electrode that does not include a negative electrode active material when the battery is assembled, but in which lithium metal or the like is precipitated or deposited on the negative electrode when the battery is charged, and this acts as a negative electrode active material.

[0152] Fig. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode. Referring to Fig. 2, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state secondary battery including such a precipitation-type negative electrode (400') starts initial charging in a state in which no negative electrode active material is present, and during charging, high-density lithium metal is precipitated or deposited between the current collector (401) and the negative electrode coating layer (405) or on the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state secondary battery that has been charged more than once, a precipitation-type negative electrode (400') may include, for example, a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The lithium metal layer (404) is a layer containing lithium, and refers to a layer in which lithium metal or the like is precipitated during the charging process of the battery, and may be referred to as a metal layer, a lithium layer, a lithium deposition layer, or a negative electrode active material layer.

[0153] The cathode coating layer (405) may be referred to as a lithium electrodeposition induction layer or a cathode catalyst layer, and may include a metal, a carbon material, or a combination thereof.

[0154] The metal may be a lithium-philic metal, and may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one type of these or may be composed of several types of alloys. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, and may be, for example, 10 nm to 4 μm, 10 nm to 1 μm, or 10 nm to 600 nm.

[0155] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof. For example, the carbon material may refer to amorphous carbon.

[0156] When the negative electrode coating layer (405) includes both a lithium-philic metal and a carbon material, the mixing ratio of the lithium-philic metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state secondary battery can be improved. The negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0157] The cathode coating layer (405) may include, for example, the above-described lithium-philic metal and amorphous carbon, in which case the precipitation of the lithium metal can be effectively promoted. As a specific example, the cathode coating layer (405) may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0158] The cathode coating layer (405) may further include a binder, which may be, for example, a conductive binder. In addition, the cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0159] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 μm, or 500 nm to 10 μm, or 1 μm to 5 μm.

[0160] The precipitation-type negative electrode (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further planarize the precipitation pattern of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0161] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, or a Li-Si alloy.

[0162] The thickness of the lithium metal layer (404) may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the lithium metal layer (404) is too thin, it may be difficult to perform the role of a lithium storage, and if it is too thick, the battery volume may increase and performance may deteriorate.

[0163] When such a precipitation-type cathode is applied, the cathode coating layer (405) can play a role in protecting the lithium metal layer (404) and suppressing the precipitation growth of lithium deadlight. Accordingly, short-circuiting and capacity reduction of the all-solid-state battery can be suppressed, and the life characteristics can be improved.

[0164] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0165] The shape of the above-mentioned all-solid-state secondary battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-mentioned all-solid-state secondary battery can be applied to large-sized batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state secondary battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage, and for example, it can be used in electric bicycles or power tools, etc. In addition, the above-mentioned all-solid-state secondary battery can be used in various fields such as portable electronic devices.

[0166] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0167] Example 1

[0168] 1. Preparation of solid electrolyte

[0169] In a glove box with an Ar atmosphere, a precursor mixture was obtained by mixing lithium precursor Li2S, copper precursor Cu2S, phosphorus precursor P2S5, zinc precursor ZnS, and halogen atom precursor LiCl. At this time, the content of each precursor was Li 5.72 Cu 0.03 P 0.985 Zn 0.015 S 4.75 Cl 1.25 was stoichiometrically controlled to obtain .

[0170] The precursor mixture was placed in a planetary ball mill containing zirconia balls in an Ar atmosphere, ground and mixed at 100 rpm for 1 hour, and then ground and mixed at 800 rpm for 30 minutes to obtain a mixture. The obtained mixture was pressed under uniaxial pressure to produce pellets with a thickness of approximately 10 mm and a diameter of approximately 13 mm. The produced pellets were covered with gold foil, placed in a carbon crucible, and the carbon crucible was vacuum-sealed. The vacuum-sealed pellets were heated at a rate of 1.0°C / min using an electric furnace, heat-treated at 475°C for 18 hours, and then cooled to room temperature at 1.0°C / min to produce the final solid electrolyte.

[0171] 2. Manufacturing of solid electrolyte membranes

[0172] A slurry was prepared by adding the prepared solid electrolyte to a binder solution in which an acrylic binder (SX-A334, Zeon) was dissolved in an isobutyryl isobutyrate (IBIB) solvent and stirring the solution. The slurry contained 98.5 wt% of the solid electrolyte and 1.5 wt% of the binder. The slurry was applied onto a release PET film using a bar coater and dried at room temperature to prepare a solid electrolyte membrane.

[0173] Examples 2 to 10 and Comparative Example 1

[0174] A solid electrolyte and a solid electrolyte membrane were manufactured in substantially the same manner as in Example 1, except that the composition of the solid electrolyte was changed as shown in Table 2 below.

[0175] It can be understood that in Examples 3, 4, and 9, SnS2 was used instead of ZnS, in Examples 5 to 8, and 10, SiS2 was used instead of ZnS, in Examples 9 and 10, Li2SO4 was additionally used as a precursor of SO4, and in Comparative Example 1, ZnS and Cu2S were not added.

[0176] Example 1 of composition of a classification system 5.765 Cu 0.03 P0.985 Zn 0.015 S 4.75 Cl 1.25 Example 2Li 5.81 Cu 0.03 P 0.97 Zn 0.03 S 4.75 Cl 1.25 Example 3Li 5.73 Cu 0.03 P 0.99 Sn 0.01 S 4.75 Cl 1.25 Example 4Li 5.75 Cu 0.03 P 0.97 Sn 0.03 S 4.75 Cl 1.25 Example 5Li 5.735 Cu 0.03 P 0.985 Si 0.015 S 4.75 Cl 1.25 Example 6Li 5.75 Cu 0.03 P 0.97 Si 0.03 S 4.75 Cl 1.25 Example 7Li 5.82 Cu 0.03 P 0.9 Si 0.1 S 4.75 Cl 1.25 Example 8Li 5.92 Cu 0.03 P 0.8 Si 0.2 S 4.75 Cl 1.25 Example 9Li 5.735 Cu 0.03 P 0.985 Sn 0.015 S 4.725 (SO4) 0.025 Cl 1.25 Example 10Li 5.75 Cu 0.03 P 0.97 Si 0.03 S 4.725 (SO4) 0.025 Cl 1.25 Comparative example 1Li 5.75 PS 4.725 Cl 1.25

[0177] Evaluation Example 1: XRD Evaluation

[0178] X-ray diffraction analysis was performed on the solid electrolytes of Examples 1 to 8, and the results are shown in FIGS. 3 and 4. Referring to FIGS. 3 and 4, it can be confirmed that there are no additional impurities other than LiCl, and accordingly, it can be seen that all of the ZnS, SnS2, or SiS2 added during synthesis participated in the argyrodite-type crystal structure, and the desired solid electrolyte was successfully synthesized.

[0179] Evaluation Example 2: Atmospheric Stability Evaluation through Ionic Conductivity Maintenance

[0180] The solid electrolytes in pellet form manufactured in Examples 1, 3, 5, 6, 9, and 10 were prepared as specimens. Indium electrodes with a thickness of 50 μm and a diameter of 13 mm were placed on both sides of the prepared specimens to prepare symmetrical cells, and the impedance was measured using the two-probe method using an impedance analyzer (Material Mates 7260 impedance analyzer). The frequency range was set to 0.1 Hz to 1 MHz, the amplitude voltage was set to 10 mV, and the measurements were performed at 25°C in an Ar atmosphere. The resistance value was obtained from the arc of the Nyquist plot for the impedance measurement results, and the ionic conductivity was calculated considering the area and thickness of the specimens. The ionic conductivity was measured immediately after the solid electrolyte synthesis, and each specimen was placed in a dry room with a dew point of -45°C or lower, and the ionic conductivity was measured one day later and again three days later. The results are shown in Table 3 below. Figure 5 is a graph showing the retention rate of ionic conductivity after being left in a dry room for 3 days compared to the ionic conductivity immediately after synthesis for the solid electrolytes of Comparative Example 1 and Examples 1, 3, 5, 6, 9, and 10.

[0181] Ionic conductivity (mS / cm) after composition storage, (retention rate, %) 0 days 1 day 3 days Example 13.1 1 2.42 (77.7%) 2.08 (67%) Example 33.3 0 2.72 (82.4%) 2.24 (68%) Example 52.3 5 1.68 (71.4%) 1.62 (69.2%) Example 62.8 2 2 (71%) 1.88 (66.7%) Example 94.0 3-3.6 (89%) Example 103.5 7 3.33 (93.3%) 3.04 (85.2%) Comparative example 12.8 0-1.82 (65.1%)

[0182] Referring to Table 3 and Figure 5, it can be seen that the solid electrolytes of the examples maintain a high level of ionic conductivity after 1 day and 3 days of standing due to the addition of moisture-stable elements within the argyrodite crystal structure, and thus, it can be seen that the atmospheric stability is improved.

[0183] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

[0184] [Explanation of symbols]

[0185] 100: All-solid-state battery 200: Cathode

[0186] 201: Cathode current collector 203: Cathode active material layer

[0187] 300: Solid electrolyte layer 400: Cathode

[0188] 401: Negative current collector 403: Negative active material layer

[0189] 404: Lithium metal layer 405: Cathode coating layer

[0190] 500: Elastic layer

Claims

1. A solid electrolyte of argyrodite type sulfide system represented by chemical formula 1: [Chemical Formula 1] (Li a M 1 b M 2 c )(P d M 3 e )(S f X 1 g )X 2 h In the above chemical formula 1, 4≤a≤8, M 1 is at least one element selected from groups 2 and 11 of the periodic table, and 0 <b<0.5이고, M 2 is at least one element other than Li selected from group 1 of the periodic table, and 0≤c<0.5, M 3 is Bi, Cu, Ge, Sb, Si, Sn, Zn or a combination thereof and 0 <d<1, 0<e<1이고, X 1 is O, N, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤7, 0≤g<2, X 2 is at least one element selected from group 17 of the periodic table, and 0 <h≤2이다.

2. In paragraph 1, In the above chemical formula 1, M 1 A solid electrolyte comprising Mg, Ca, Cu, Ag, or a combination thereof.

3. In paragraph 1, A solid electrolyte in which 0.001≤b≤0.1 in the above chemical formula 1.

4. In paragraph 1, A solid electrolyte in which 0.001≤b / (a+b+c)≤0.05 in the above chemical formula 1.

5. In paragraph 1, In the above chemical formula 1, M 2 A solid electrolyte comprising Na, K, or a combination thereof, and 0≤c≤0.

3.

6. In paragraph 1, A solid electrolyte in which 0.9≤d+e≤1.1, 0.7≤d≤0.99, and 0.01≤e≤0.3 in the above chemical formula 1.

7. In paragraph 1, A solid electrolyte in which 0.01≤e / (d+e)≤0.3 in the above chemical formula 1.

8. In paragraph 1, In the above chemical formula 1, A solid electrolyte with 3≤f≤5 and 0.01≤g≤0.

9.

9. In paragraph 1, A solid electrolyte in which 0.01≤g / (f+g)≤0.3 in the above chemical formula 1.

10. In paragraph 1, In the above chemical formula 1, X 2 A solid electrolyte wherein the electrolyte is Cl, Br, or a combination thereof, and 1≤h≤2.

11. In paragraph 1, The above chemical formula 1 is a solid electrolyte represented by the chemical formula 2 below: [Chemical Formula 2] (Li a Cu b )(P d M 3 e )(S f X 1 g )X 2 h In the above chemical formula 2, 4≤a≤8, and 0 <b<0.5이고, M 3 is Bi, Cu, Ge, Sb, Si, Sn, Zn or a combination thereof and 0 <d<1, 0<e<1이고, X 1 is O, N, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤7, 0≤g<2, X 2 is at least one element selected from group 17 of the periodic table, and 0 <h≤2이다.

12. In paragraph 1, M 3 A solid electrolyte comprising Cu, Si, Sn, Zn, or a combination thereof.

13. In paragraph 1, The above chemical formula 1 is a solid electrolyte represented by the chemical formulas below. (1) Li 5.765 I will 0.03 P 0.985 Zn 0.015 WITH 4.75 Cl 1.25 (2) Li 5.81 I will 0.03 P 0.97 Zn 0.03 WITH 4.75 Cl 1.25 (3) Li 5.73 With 0.03 P 0.99 Sn 0.01 S 4.75 Cl 1.25 (4) Li 5.75 With 0.03 P 0.97 Sn 0.03 S 4.75 Cl 1.25 (5) Li 5.735 I will 0.03 P 0.985 Yes 0.015 WITH 4.75 Cl 1.25 (6) Li 5.75 I will 0.03 P 0.97 Yes 0.03 WITH 4.75 Cl 1.25 (7) Lee 5.82 I will 0.03 P 0.9 Yes 0.1 WITH 4.75 Cl 1.25 (8) Lee 5.92 I will 0.03 P 0.8 Yes 0.2 WITH 4.75 Cl 1.25 (9) Li 5.735 With 0.03 P 0.985 Sn 0.015 S 4.725 (SO4) 0.025 Cl 1.25 (10) Li 5.75 With 0.03 P 0.97 And 0.03 S 4.725 (SO4) 0.025 Cl 1.25 (11) Li 6.02 With 0.03 P 0.7 Sn 0.3 S 4.75 and 1.25 (12) Li 6.02 With 0.03 P 0.7 Sn 0.3 S 4.75 and 1.25 14. In paragraph 1, A solid electrolyte having an ionic conductivity of 2.0 mS / cm or more at 25°C.

15. In paragraph 1, The above solid electrolyte is in the form of particles, and its average particle diameter (D 50 ) is a solid electrolyte having a particle size of 0.1 ㎛ to 5 ㎛.

16. A solid electrolyte membrane comprising a solid electrolyte according to any one of claims 1 to 15.

17. In paragraph 16, A solid electrolyte membrane having a thickness of 100 ㎛ to 1000 ㎛.

18. Bipolar, cathode, and including a solid electrolyte membrane positioned between the anode and the cathode, An all-solid-state secondary battery, wherein at least one of the positive electrode, the negative electrode, and the solid electrolyte membrane comprises a solid electrolyte according to any one of claims 1 to 15.

19. Bipolar, cathode, and An all-solid-state secondary battery comprising a solid electrolyte membrane according to claim 16 positioned between the positive electrode and the negative electrode.

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