All-solid-state batteries

Abstract

The present invention relates to an all-solid-state battery, the all-solid-state battery including a negative electrode, an electrolyte layer, and a positive electrode including a positive electrode layer and a current collector supporting the positive electrode layer, the positive electrode layer including a first region in contact with the electrolyte layer and a second region in contact with the positive electrode current collector, the first region including particles of a first solid electrolyte, the second region including particles of a second solid electrolyte, and the average particle size of the particles of the first solid electrolyte being larger than the average particle size of the particles of the second solid electrolyte.

Description

[Technical Field]

[0001] This relates to all-solid-state batteries. [Background technology]

[0002] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for small, lightweight, and relatively high-capacity secondary batteries has been growing rapidly. In particular, lithium secondary batteries have attracted attention as a power source for portable devices due to their light weight and high energy density. As a result, research and development efforts to improve the performance of lithium secondary batteries have been actively pursued.

[0003] Among lithium secondary batteries, all-solid-state batteries are batteries that are made entirely of solid materials, particularly those that use a solid electrolyte. Such all-solid-state batteries have the advantages of being safe because there is no risk of electrolyte leakage, and being easy to fabricate into thin batteries.

[0004] In solid-state batteries, ion transport occurs through physical contact between the positive or negative electrode and the solid electrolyte, so the contact area between the positive or negative electrode and the solid electrolyte is important. To increase this contact area, methods have been studied to reduce the particle size of the solid electrolyte, but this has led to problems such as increased interfacial resistance and reduced rapid charge / discharge performance of the battery. Summary of the Invention [Problem to be solved by the invention]

[0005] One embodiment provides an all-solid-state battery with excellent rapid charge / discharge performance and capacity. [Means for solving the problem]

[0006] One embodiment provides an all-solid-state battery comprising: an anode; an electrolyte layer; and a cathode comprising a cathode layer and a current collector supporting the cathode layer, wherein the cathode layer comprises a first region in contact with the electrolyte layer and a second region in contact with the cathode current collector, wherein the first region comprises particles of a first solid electrolyte, and the second region comprises particles of a second solid electrolyte, and wherein the average particle size of the particles of the first solid electrolyte is larger than the average particle size of the particles of the second solid electrolyte.

[0007] The ratio of the average particle size of the second solid electrolyte particles to the average particle size of the first solid electrolyte particles may be 1:1.1 to 1:40.

[0008] The positive electrode layer may include the first region and the second region.

[0009] The first region may have a thickness of 70% or less of the total thickness of the positive electrode layer, and the second region may have a thickness of 30% or more of the total thickness of the positive electrode layer.

[0010] The first solid electrolyte particles may include large solid electrolyte particles and small solid electrolyte particles, and the second solid electrolyte particles may include small solid electrolyte particles. According to one embodiment, the first solid electrolyte particles are large solid electrolyte particles and small solid electrolyte particles, and the second solid electrolyte particles are small solid electrolyte particles.

[0011] The average particle size ratio of the small solid electrolyte particles to the large solid electrolyte particles may be 1:1.5 to 1:40.

[0012] The large particles of the solid electrolyte may have an average particle size of 1 μm to 20 μm, and the small particles of the solid electrolyte may have an average particle size of 0.1 μm to 5 μm.

[0013] The thickness ratio of the first region and the second region may be between 70:30 and 30:70.

[0014] The positive electrode layer may include a third region between the first region and the second region. The third region may include particles of a third solid electrolyte, and the particles of the third solid electrolyte may have a gradient in which the average particle size increases from a second surface in contact with the second region toward a first surface in contact with the first region. In this case, the first region may correspond to a thickness of 24% or more and 56% or less of the total thickness of the positive electrode layer, and the second region may correspond to a thickness of 24% or more and 56% or less of the total thickness of the positive electrode layer. Furthermore, the third region may correspond to 20% to 50% of the total thickness of the positive electrode layer.

[0015] The average particle size of the third solid electrolyte particles on the second surface may be 0.1 μm to 5 μm, and the average particle size of the third solid electrolyte particles on the first surface may be 1 μm to 20 μm.

[0016] The particle size ratio of the first solid electrolyte particles in the first region to the particle size of the second solid electrolyte particles in the second region is 1.1 / 1 or more and less than 5 / 1, and when the second surface in contact with the second region is 0% and the first surface in contact with the first region is 100%, the average particle size of the third solid electrolyte in the third region at positions increasing by 10% in a thickness direction from the second surface to the first surface of the positive electrode layer can increase by 1% to 40%.

[0017] According to another embodiment, the particle size ratio of the first solid electrolyte particles in the first region to the particle size of the second solid electrolyte particles in the second region is 5 / 1 or more and 40 / 1 or less, and when the second surface in contact with the second region is 0% and the first surface in contact with the first region is 100%, the average particle size of the third solid electrolyte in the third region at a position where the particle size increases by 10% in a thickness direction from the second surface to the first surface of the positive electrode layer can increase by 40% to 390%.

[0018] The third region may be divided into two to five sections in the thickness direction, and the average particle size of the third solid electrolyte particles in each section may be different from each other.

[0019] The third region may be divided into two to five sections in the thickness direction, with a section in contact with the first region being a first section and a section in contact with the second region being an n section, and the average particle size of the particles of the third solid electrolyte may increase from the n section toward the first section. [Effects of the Invention]

[0020] An all-solid-state battery according to an embodiment can improve the rapid charge / discharge performance and capacity of the battery. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a positive electrode of an all-solid-state battery according to one embodiment. [Figure 2] FIG. 10 is a cross-sectional view schematically illustrating a positive electrode of an all-solid-state battery according to another embodiment. [Figure 3] FIG. 1 is a cross-sectional view schematically illustrating an all-solid-state battery according to an embodiment. [Figure 4] FIG. 10 is a cross-sectional view schematically illustrating an all-solid-state battery according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the present invention is given by way of example only and is not intended to limit the scope of the present invention, which is defined solely by the claims.

[0023] Unless otherwise specified in this specification, when a layer, film, region, plate, or other part is said to be "on" another part, this includes not only when it is "directly on" the other part, but also when there is another part between them.

[0024] In the present invention, "particle size" and "particle diameter" refer to an average particle diameter. The average particle diameter can be defined as the average particle diameter (D50) at 50% of the cumulative volume on a particle size distribution curve. The particle diameter can be measured by electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), or the like, or by a laser diffraction method. Specifically, when measuring by the laser diffraction method, particles to be measured are dispersed in a dispersion medium, introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac's MT3000), and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W. The average particle diameter (D50) at 50% of the particle size distribution measured by the analyzer can then be calculated.

[0025] According to one embodiment, an all-solid-state battery includes an anode, an electrolyte layer, and a cathode, wherein the cathode includes a cathode layer and a current collector supporting the cathode layer, and the cathode layer includes a first region in contact with the electrolyte layer and a second region in contact with the cathode current collector. In one embodiment, the first region includes particles of the first solid electrolyte, and the second region includes particles of a second solid electrolyte, and the average particle size of the particles of the first solid electrolyte may be larger than the average particle size of the particles of the second solid electrolyte.

[0026] The all-solid-state battery can also be referred to as an all-solid-state secondary battery or an all-solid-state lithium secondary battery.

[0027] The ratio of the average particle size of the second solid electrolyte particles to the average particle size of the first solid electrolyte particles may be 1:1.1 to 40, 1:1.1 to 20, 1:1.5 to 10, 1:1.5 to 5, or 1:2 to 4.

[0028] In this way, the first region adjacent to the electrolyte layer contains particles of the first solid electrolyte with a large average particle size, which increases lithium ion conductivity and improves rapid charge / discharge characteristics and life characteristics. Furthermore, the second region adjacent to the current collector contains particles of the second solid electrolyte with a small average particle size, which increases the contact area with the positive electrode active material and therefore increases capacity. Furthermore, the inclusion of particles of the second solid electrolyte with a small average particle size in the second region adjacent to the current collector increases the number of ion transport paths.

[0029] In this way, the effect of using solid electrolyte particles having different average particle sizes depending on the position in the positive electrode layer can be more effectively obtained when the ratio of the average particle size of the first solid electrolyte particles to the average particle size of the second solid electrolyte particles is within the above range.

[0030] In one embodiment, the cathode layer may be composed of the first and second regions. That is, the cathode layer may be divided into two regions. Referring to FIG. 1 , the cathode 1 includes a current collector 3 and a cathode layer 5. The cathode 1 includes a first region 5a adjacent to the electrolyte layer, i.e., not adjacent to the current collector, and a second region 5b adjacent to the current collector 3. The average particle size of the first solid electrolyte particles in the first region 5a may be larger than the average particle size of the second solid electrolyte particles in the second region 5b. Only the first and second solid electrolyte particles are shown in the first region 5a and the second region 5b in FIG. 1, and all other solid electrolyte particles are omitted.

[0031] In one embodiment, the first region represents a region that is 70% or less of the total thickness of the positive electrode layer, i.e., the region a in Fig. 1 represents a region that is 70% or less of the total thickness h of the positive electrode layer. The second region represents a region that is 30% or more of the total thickness of the positive electrode layer, i.e., the region b in Fig. 1 represents a region that is 30% or more of the total thickness h of the positive electrode layer.

[0032] When the positive electrode layer is composed of the first region and the second region, the first solid electrolyte particles may include large solid electrolyte particles and small solid electrolyte particles, and the second solid electrolyte particles may include small solid electrolyte particles. More specifically, the first solid electrolyte particles in the first region may have different particle sizes, i.e., include large solid electrolyte particles and small solid electrolyte particles, and the second solid electrolyte particles in the second region may include particles having a substantially uniform size, i.e., include only small particles.

[0033] In this case, the average particle size ratio of the small particles of the solid electrolyte to the large particles of the solid electrolyte may be 1:1.5 to 1:40, 1:1.5 to 1:20, 1:1.5 to 1:10, 1:2 to 1:5, or 1:2 to 1:4.

[0034] When the first region includes large particles and small particles, the surface area of ​​the solid electrolyte can be further increased compared to when the first region includes only large particles. In particular, when the first solid electrolyte particles include large solid electrolyte particles and small solid electrolyte particles having the above average particle size ratio, the number of connections between the active material and the solid electrolyte can be further increased.

[0035] In one embodiment, the average particle size of the large particles of the solid electrolyte may be 1 μm to 20 μm, 1 μm to 10 μm, 1.5 μm to 10 μm, or 2 μm to 5 μm. The average particle size of the small particles of the solid electrolyte may be 0.1 μm to 5 μm, 0.5 μm to 4 μm, or 0.5 μm to 3 μm. When the average particle size of the large particles of the solid electrolyte is within this range, the critical resistance may be further reduced and the conductivity may be further improved. Furthermore, when the average particle size of the small particles of the solid electrolyte is within this range, the porosity of the positive electrode plate may be reduced.

[0036] The thickness ratio of the first region to the second region may be 70:30 to 30:70. When the thickness ratio of the first region to the second region falls within this range, the ionic resistance of the positive electrode can be further reduced.

[0037] The positive electrode layer including the first region and the second region can be formed by applying a second positive electrode layer composition including particles of the second solid electrolyte to a current collector, drying the composition, and then applying particles of the first solid electrolyte and drying the composition.

[0038] According to another embodiment, the positive electrode layer may further include a third region between the first region and the second region. In this structure, as shown in Fig. 2, a positive electrode 1' includes a current collector 3' and a positive electrode layer 5', and includes a first region 5a' adjacent to the electrolyte layer, i.e., not adjacent to the current collector 3', a second region 5b' adjacent to the current collector 3', and a third region 5c' located between the first region 5a' and the second region 5b'.

[0039] When the positive electrode layer further includes a third region, the third region may have a thickness of 20% to 50% of the total thickness of the positive electrode layer.

[0040] In this case, the first region may correspond to a thickness of 24% or more and 56% or less of the total thickness (100%) of the positive electrode layer, and the second region may correspond to a thickness of 24% or more and 56% or less of the total thickness (100%) of the positive electrode layer. That is, the thickness a' corresponding to the first region shown in Figure 2 may be 24% or more and 56% or less of the total thickness h of the positive electrode layer, and the thickness b' corresponding to the second region may be 56% or more and 24% or less of the total thickness h of the positive electrode layer.

[0041] The average particle diameters of the first solid electrolyte particles and the second solid electrolyte particles contained in the first and second regions are the same as those described above.

[0042] The third region also includes solid electrolyte particles (hereinafter referred to as third solid electrolyte particles), and the average particle size of the third solid electrolyte particles may have a gradient. The gradient of the average particle size of the third solid electrolyte particles may increase gradually or stepwise.

[0043] When the average particle size gradually increases, the particles of the third solid electrolyte may have a gradient in which the average particle size increases from the second surface in contact with the second region toward the first surface in contact with the first region, where the second surface in contact with the second region is 0% and the first surface in contact with the first region is 100%, forming a gradient from the second surface to the first surface.

[0044] When the average particle size gradient of the third solid electrolyte particles gradually increases, the gradient can be appropriately adjusted by adjusting the particle size ratio between the first solid electrolyte particles in the first region and the second solid electrolyte particles in the second region. For example, when the particle size ratio of the first solid electrolyte particles in the first region to the second solid electrolyte particles in the second region is 1.1 / 1 or greater and less than 5 / 1, the particle size of the third solid electrolyte particles at a position where the particle size increases by 10% from the second surface to the first surface, i.e., in the thickness direction, may increase by 1% to 40%. In this case, the increase in particle size means 1% to 40% of the initial particle size, i.e., 1% to 40% of the particle size of the third solid electrolyte particles at the second surface. For example, when the particle size of the third solid electrolyte at the second surface is 0.1 μm, the particle size of the third solid electrolyte at a position where the particle size increases by 10% in the thickness direction may be 0.101 μm to 0.14 μm, and at a position where the particle size increases by 20% may be 0.102 μm to 0.18 μm.

[0045] According to another embodiment, when the particle size ratio of the first solid electrolyte particles in the first region to the particle size of the second solid electrolyte particles in the second region is 5 / 1 or more and 40 / 1 or less, the average particle size of the third solid electrolyte in the third region at a position where the thickness increases by 10% from the second surface to the first surface of the positive electrode layer may increase by 40% to 390%. In this case, the increased particle size value means 40% to 390% of the initial particle size, i.e., 40% to 390% of the particle size of the third solid electrolyte particles at the second surface. For example, when the particle size of the third solid electrolyte at the second surface is 1 μm, the particle size of the third solid electrolyte at a position where the thickness increases by 10% may be 4.9 μm, and at a position where the thickness increases by 20% may be 8.8 μm.

[0046] In the third region, if the average particle size of the solid electrolyte particles increases in the direction from the second surface to the first surface, the ionic resistance of the positive electrode can be further reduced. In particular, if the increase satisfies this condition, the ionic resistance of the positive electrode can be more effectively reduced.

[0047] When the solid electrolyte particles in the third region increase stepwise from the second surface to the first surface, the third region may be divided into two to five sections, and the average particle size of the solid electrolyte particles in each section may be different. In contrast, the third region may be divided into two to five sections in a thickness direction, and when a section in contact with the first region is a first section and a section in contact with the second region is an n section, the average particle size of the solid electrolyte particles may increase from the n section toward the first section.

[0048] The average particle size of the third solid electrolyte particles on the second surface may be 0.1 μm to 5 μm, and the average particle size of the third solid electrolyte particles on the first surface may be 1 μm to 20 μm.

[0049] When the average particle size of the third solid electrolyte particles on the second surface and the average particle size of the third solid electrolyte particles on the first surface are within the above ranges, the positive electrode voids can be further reduced, and the ionic resistance can be further reduced.

[0050] The gradual increase in the average particle size of the solid electrolyte particles in the third region can be achieved by coating the current collector with a composition for forming a positive electrode layer multiple times, with the average particle size of the solid electrolyte particles contained in the composition being varied. That is, the solid electrolyte particles contained in the composition for forming a positive electrode layer that is directly coated on the current collector can have a small average particle size, and when coating is performed multiple times, i.e., the number of coatings increases, the average particle size of the solid electrolyte particles can be increased.

[0051] With each additional coating, the average particle size of the solid electrolyte particles can be increased by 2% to 780% of the initial average particle size of the solid electrolyte particles. The average particle size of the solid electrolyte particles on the second surface in contact with the second region can be 0.1 μm to 5 μm, and finally, the average particle size of the solid electrolyte particles in the nth region in contact with the first region in contact with the electrolyte layer can be 1 μm to 20 μm.

[0052] The solid electrolyte may be a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

[0053] Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiX (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, and Li2S-P2S5-Z. m S n (m and n are integers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In).

[0054] For example, the sulfide-based solid electrolyte may be obtained by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10 or 50:50 to 80:20. This mixing ratio range allows for the production of a sulfide-based solid electrolyte with excellent ionic conductivity. Additional components, such as SiS2, GeS2, and B2S3, may be added to further improve ionic conductivity. Mixing methods include mechanical milling and solution milling. Mechanical milling involves vigorously mixing the starting materials in a reactor with a ball mill to finely grind them. When using the solution milling method, the starting materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. After mixing, additional calcination can be performed. Additional calcination can further harden the crystals of the solid electrolyte.

[0055] For example, the solid electrolyte may be an argyrodite-type sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be, for example, Li a M b P c S d A e (a, b, c, d, and e are all 0 to 12, M is Ge, Sn, Si, or a combination thereof, and A is one of F, Cl, Br, or I), specifically Li3PS4, Li7P3S 11 , Li6PS5Cl, Li6PS5Br, Li6PS5I, etc.

[0056] The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof. Of course, commercially available solid electrolytes may also be used as the sulfide-based solid electrolyte.

[0057] The oxide-based inorganic solid electrolyte may be, 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 O12 (0 < x < 2, 0 ≤ y < 3), BaTiO3, Pb(Zr, Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (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[[ID=​​​​​​​​​​​​​​​​​​​

[0060] The total content of the first solid electrolyte particles, the second solid electrolyte particles, and the third solid electrolyte particles in the positive electrode layer may be 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 %, based on the total weight of the positive electrode layer. Furthermore, the positive electrode layer may contain 65 wt % to 99 wt % of the positive electrode active material and 1 wt % to 35 wt % of the solid electrolyte, based on the total weight of the positive electrode active material and the solid electrolyte. For example, the positive electrode layer may contain 80 wt % to 90 wt % of the positive electrode active material and 10 wt % to 20 wt % of the solid electrolyte. When the solid electrolyte is contained in the positive electrode in such a content, the efficiency and lifespan characteristics of the all-solid-state battery can be improved without reducing the capacity.

[0061] It is only necessary to adjust the total content of the solid electrolyte particles contained in the positive electrode layer, and it is not necessary to adjust the content of the solid electrolyte particles contained in each region.

[0062] The positive electrode layer includes a positive electrode active material.

[0063] The positive electrode active material may be a positive electrode active material capable of reversibly absorbing and releasing lithium ions. For example, the positive electrode active material may be one or more of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. Specific examples of the positive electrode active material include Li a A 1-b B 1 b D 1 2(0.90≦a≦1.8, 0≦b≦0.5);Li a E 1-b B 1 b O 2-c D 1 c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5);Li a E 2-b B 1 b O 4-cD 1 c (0.90≦a≦1.8、0≦b≦0.5、0≦c≦05);Li a Ni 1-b-c Co b B 1 c D 1 α (0.90≦a≦1.8、0≦b≦0.5、0≦c≦0.5、0<α≦2);Li a Ni 1-b-c Co b B 1 c O 2-α F 1 α (0.90≦a≦1.8、0≦b≦0.5、0≦c≦0.5、0<α<2);Li a Ni 1-b-c Co b B 1 c O 2-α F 1 2(0.90≦a≦1.8、0≦b≦0.5、0≦c≦0.5、0<α<2);Li a Ni 1-b-c Mr b B 1 c D 1 α (0.90≦a≦1.8、0≦b≦0.5、0≦c≦0.5、0<α≦2);Li a Ni 1-b-c Mr b B 1 c O 2-α F 1 α (0.90≦a≦1.8、0≦b≦0.5、0≦c≦0.5、0<α<2);Li a Ni 1-b-c Mr b B 1 c O 2-α F 1 2(0.90≦a≦1.8、0≦b≦0.5、0≦c≦0.5、0<α<2);Li a Ni b HAVE BEEN c G d O2(0.90≦a≦1.8、0≦b≦0.9、0≦c≦0.5、0.001≦d≦0.1);Lia 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 MnG 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);QO2;QS2;LiQS2;V2O5;LiV2O5;LiI 1 O2;LiNiVO4;Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3 (0≦f≦2); or LiFePO4.

[0064] In the above formula, A is Ni, Co, Mn, or a combination thereof; B 1 is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or combinations thereof; D 1 is O, F, S, P, or a combination thereof, and E is Co, Mn, or a combination thereof; F 1 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 1 is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0065] According to one embodiment, the positive electrode active material is LiNi xCo y Al z O2(NCA), LiNi x Co y Mn z Examples thereof include ternary lithium transition metal oxides such as O2(NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1).

[0066] Of course, those having a coating layer on the surface of the compound can also be used, or the compound and a compound having a coating layer can be mixed and used. The coating layer can contain at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds constituting these coating layers can be amorphous or crystalline. As the coating element contained in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof can be used. As long as the coating layer formation process can coat the compound with such elements in a method that does not adversely affect the physical properties of the positive electrode active material (for example, spray coating, dipping method, etc.), any coating method can be used, and since this is well understood by those skilled in the art, detailed description thereof is omitted.

[0067] In addition, as the coating layer, any known coating layer for the positive electrode active material of an all-solid-state battery can be applied, and examples thereof include Li2O-ZrO2 (LZO).

[0068] Here, examples of the shape of the positive electrode active material include particle shapes such as spherical and oval spheres. The average particle size of the positive electrode active material is not particularly limited, and may be within a range applicable to positive electrode active materials in existing all-solid-state secondary batteries. The content of the positive electrode active material in the positive electrode active material layer is also not particularly limited, and may be within a range applicable to positive electrode layers in existing all-solid-state secondary batteries.

[0069] In one embodiment, the positive electrode active material may be included in an amount of 55 wt % to 99.7 wt %, for example, 74 wt % to 89.8 wt %, based on the total weight of the positive electrode layer, which may maximize the capacity of the all-solid-state battery and improve its lifespan characteristics.

[0070] The positive electrode layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode and may be any electron-conductive material that does not undergo chemical changes. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, and the like; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0071] The conductive material may be contained in an amount of 0.1 to 5 wt %, or 0.1 to 3 wt %, based on the total weight of each component of the positive electrode for the all-solid-state battery, or based on the total weight of the positive electrode layer. The conductive material in this content range can improve conductivity without deteriorating battery performance.

[0072] The current collector may comprise, 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), or an alloy thereof, and may be in foil or sheet form.

[0073] The negative electrode includes a current collector and a negative electrode layer disposed on one surface of the current collector.

[0074] The negative electrode layer may be a negative electrode active material layer, a negative electrode coating layer, or a lithium metal layer.

[0075] The negative electrode active material layer includes a negative electrode active material, and may further include a binder, a conductive material, and / or a solid electrolyte.

[0076] The negative electrode active material may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped and dedoped with lithium, or a transition metal oxide.

[0077] The material capable of reversibly intercalating / deintercalating lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite, such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite. Examples of the amorphous carbon include soft or hard carbon, mesophase pitch carbide, and calcined coke.

[0078] The lithium metal alloy may be an alloy of lithium and one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0079] The material capable of doping and dedoping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. Examples of the Si-based negative electrode active material include silicon, silicon-carbon composites, and SiO x(0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and there is no Si), examples of the Sn-based negative electrode active material include Sn, SnO2, Sn-R alloy (where R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and there is no Sn), etc., and at least one of these can be mixed with SiO2 and used. As the elements Q and R, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof can be used.

[0080] The silicon-carbon composite may be, for example, a silicon-carbon composite including a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon can be artificial graphite, natural graphite, or a combination thereof. As the amorphous carbon precursor, coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or polymer resins such as phenolic resin, furan resin, polyimide resin can be used. At that time, the content of silicon can be 10% to 50% by weight based on the total weight of the silicon-carbon composite. Also, the content of the crystalline carbon can be 10% to 70% by weight based on the total weight of the silicon-carbon composite, and the content of the amorphous carbon can be 20% to 40% by weight based on the total weight of the silicon-carbon composite. Also, the thickness of the amorphous carbon coating layer can be 5 nm to 100 nm.

[0081] The silicon particles may have an average particle size (D50) of 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles may be present in an oxidized form, and the atomic content ratio of Si:O in the silicon particles, which indicates the degree of oxidation, may be 99:1 to 33:67. The silicon particles may be SiO x particles, where SiO x The range of x in the formula (1) can be greater than 0 and less than 2. Here, the average particle size (D50) is measured with a particle size analyzer using a laser diffraction method, and refers to the diameter of particles that make up 50% by volume of the cumulative volume in the particle size distribution.

[0082] The Si-based or Sn-based negative electrode active material may be mixed with a carbon-based negative electrode active material, and the mixing ratio of the Si-based or Sn-based negative electrode active material to the carbon-based negative electrode active material may be 1:99 to 90:10 by weight.

[0083] The content of the negative electrode active material in the negative electrode active material layer may be 95 wt % to 99 wt % based on the total weight of the negative electrode active material layer.

[0084] In one embodiment, the negative electrode active material layer may further include a binder and, optionally, a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt % to 5 wt % based on the total weight of the negative electrode active material layer. When the conductive material is further included, the negative electrode active material layer may include 90 wt % to 98 wt % of the negative electrode active material, 1 wt % to 5 wt % of the binder, and 1 wt % to 5 wt % of the conductive material.

[0085] The binder serves to firmly adhere the negative active material particles to each other and to the current collector, and may include a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0086] The water-insoluble binder may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0087] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylate-based styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0088] When a water-soluble binder is used as the negative electrode binder, it may be used together with a thickener that can impart viscosity. The thickener may include, for example, a cellulose-based compound. The cellulose-based compound may include carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, alkali metal salts thereof, or combinations thereof. The alkali metal may be sodium, potassium, or lithium. The content of such a thickener may be 0.1 to 3 parts by weight per 100 parts by weight of the negative electrode active material. The cellulose-based compound may also function as a binder.

[0089] The binder is not limited to these, and any binder that is used as a binder in the relevant technical field can be used, and the content of these can also be adjusted as appropriate.

[0090] The conductive material is used to impart conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and carbon nanotubes; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0091] The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0092] When the negative electrode layer is a negative electrode coating layer, the negative electrode is referred to as a deposition-type negative electrode. A deposition-type negative electrode is a negative electrode that does not contain a negative electrode active material when the battery is assembled, but deposits lithium metal or the like during battery charging, acting as the negative electrode active material. More specifically, during charging of an all-solid-state battery, lithium ions are released from the positive electrode active material, pass through the solid electrolyte, and migrate to the negative electrode. They are then deposited on the negative electrode current collector, resulting in the formation of a lithium deposition layer between the current collector and the negative electrode coating layer. A negative electrode having such a lithium deposition layer is referred to as a deposition-type negative electrode.

[0093] That is, a lithium deposit layer may be formed between the negative electrode current collector and the negative electrode layer.

[0094] The charging step may be a formation step carried out 1 to 3 times at about 25°C to 50°C and 0.05C to 1C.

[0095] The thickness of the lithium deposition layer may be 10 μm to 50 μm. For example, the thickness of the lithium deposition layer may be 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more, or 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. When the thickness of the lithium deposition layer is within this range, lithium is reversibly deposited during charge / discharge, which may have the advantage of further improving the lifespan.

[0096] The negative electrode coating layer may include a metal, a carbon material, or a combination thereof, which functions as a catalyst. In the negative electrode coating layer, for example, a metal may be supported on a carbon material, or a mixture of a metal and a carbon material may be present. In one embodiment, the negative electrode coating layer may include a metal and a carbon material.

[0097] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof, or may be amorphous carbon. 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, acetylene black, denka black, ketjen black, furnace black, activated carbon, graphene, or a combination thereof. An example of the carbon black is Super P (Timcal). The amorphous carbon is not limited to this, and any material classified as amorphous carbon in the field may be used.

[0098] The amorphous carbon may be in the form of a single particle, a secondary particle formed by agglomeration of a plurality of primary particles, or a combination thereof.

[0099] The diameter of the single particle may be 10 nm to 60 mm, the diameter of the primary particle may be 20 nm to 100 nm, and the diameter of the secondary particle may be 1 μm to 20 μm.

[0100] In one embodiment, the particle size of the primary particles may be 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, or 90 nm or more, and may be 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less.

[0101] In one embodiment, the particle size of the secondary particles may be 1 μm or more, 3 μm or more, 5 μm or more, 7 μm or more, 10 μm or more, or 15 μm or more, and may be 20 μm or less, 15 μm or less, 10 μm or less, 7 μm or less, 5 μm or less, or 3 μm or less.

[0102] The morphology of the primary particles may be spherical, ellipsoidal, plate-like, and combinations thereof, and in one embodiment, the morphology of the primary particles may be spherical, ellipsoidal, and combinations thereof.

[0103] The metal may be any one selected from Ag, Zn, Al, Sn, Mg, Ge, Cu, In, Ni, Bi, Au, Si, Pt, Pd, and combinations thereof, and in one embodiment, may be Ag. When the negative electrode coating layer includes the metal, the conductivity of the negative electrode can be improved.

[0104] The metal may be metal particles, and the metal particles may have a size of 5 nm to 800 nm. The size of the metal particles may be 5 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm or more, 450 nm or more, 500 nm or more, 550 nm or more, 600 nm or more, 650 nm or more, 700 nm or more, or 750 nm or more. The size of the metal particles may be 800 nm or less, 750 nm or less, 700 nm or less, 650 nm or less, 600 nm or less, 550 nm or less, 500 nm or less, 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, or 50 nm or less. When the size of the metal particles is within the above range, the battery characteristics (for example, life characteristics) of the all-solid-state battery can be improved.

[0105] When the negative electrode coating layer includes a carbonaceous material and metal particles, the mixing ratio of the carbonaceous material to the metal particles may be 1:1 to 99:1 by weight. For example, the weight of the carbonaceous material relative to the weight of the metal particles may be 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 55 or more, 60 or more, 65 or more, 70 or more, 75 or more, 80 or more, 85 or more, 90 or more, or 95 or more, or 99 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 5 or less, 4 or less, 3 or less, or 2 or less. For example, the weight ratio of the carbon-based material to the metal particles may be 1:1 to 5:1, 1:1 to 10:1, 1:1 to 20:1, 1:1 to 30:1, 1:1 to 40:1, 1:1 to 50:1, 1:1 to 60:1, 1:1 to 70:1, 1:1 to 80:1, or 1:1 to 90:1. When the carbon-based material and the metal particles are contained in the above weight ratio, the conductivity of the negative electrode can be further improved.

[0106] The negative electrode coating layer may further include a binder, a conductive material, and / or a solid electrolyte.

[0107] The binder and the conductive material are the same as those described in the negative electrode active material layer.

[0108] The solid electrolyte may be a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof, as described above for the positive electrode. The solid electrolyte contained in the negative electrode may be the same as or different from the solid electrolyte contained in the positive electrode.

[0109] The negative electrode layer may further contain additives such as a filler, a dispersant, an ion conductive material, etc. In addition, known materials generally used in all-solid-state batteries may be used as the filler, dispersant, ion conductive material, etc. that can be contained in the negative electrode layer.

[0110] The thickness of the negative electrode coating layer may be 1 μm to 15 μm, and may be 5 μm to 10 μm.

[0111] The current collector may be, 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), or an alloy thereof, and may be in the form of a foil or sheet. The thickness of the current collector may be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0112] The electrolyte layer may include a solid electrolyte, which may be an inorganic solid electrolyte such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a halide-based solid electrolyte, or a solid polymer electrolyte.

[0113] The sulfide-based solid electrolyte and the oxide-based solid electrolyte are as described above, and may be the same as or different from the solid electrolyte contained in the positive electrode or the negative electrode.

[0114] Examples of the solid polymer electrolyte include polyethylene oxide, poly(diallyldimethylammonium), trifluoromethanesulfonylimide (poly(diallyldimethylammonium)TFSI), Cu3N, Li3N, LiPON, Li3PO4·Li2S·SiS2, Li2S·GeS2·Ga2S3, Li2O·11Al2O3, Na2O·11Al2O3, (Na, Li) 1+x Ti 2-x Al x (PO4)3(0.1≦x≦0.9), Li 1+x Hf 2-x Al x (PO4)3(0.1≦x≦0.9), Na3Zr2Si2PO 12 , Li3Zr2Si2PO 12 , Na5ZrP3O 12 , NaTiP0 12 , Na3Fe2P3O 12 , Na4NbP3O 12 , Na-Silicates, Li 0.3 La 0.5 TiO3, Na5MSi4O 12 (M is a rare earth element such as Nd, Gd, or Dy) Li5ZrP3O 12 , Li5TiP3O 12 , LiFeP0 12 , Li4NbP3O 12 , Li 1+x (M, Al, Ga) x (Ge 1-y Ti y ) 2-x (PO4)3 (x≦0.8, 0≦y≦1.0, M is Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), Li 1+x+y Q x Ti 2-x Si y P 3-y O 12 (0 <x≦0.4、0<y≦0.6、Qは、AlまたはGa)、Li6BaLa2Ta2O 12 , Li7La3Zr2O 12 , Li5La3Nb2O 12 , Li5La3M2O 12(M is Nb, Ta), and Li 7+x A x La 3-x Zr2O 12 It can contain one or more selected from (0 < x < 3, A is Zn).

[0115] The halide solid electrolyte can contain a Li element, an M element (M is a metal other than Li), and an X element (X is a halogen). Examples of X include F, Cl, Br, and I. In particular, for the halide solid electrolyte, at least one of Br and Cl is suitable as the X. Examples of the M include metal elements such as Sc, Y, B, Al, Ga, and In.

[0116] The composition of the halide solid electrolyte is not particularly limited, but Li 6-3a M a Br b Cl c (where M is a metal other than Li, 0 < a < 2, 0 ≤ b ≤ 6, 0 ≤ c ≤ b, b + c = 6). At that time, the a can be 0.75 or more, can be 1 or more, and a can be 1.5 or less. The b can be 1 or more, can be 2 or more. Also, the c can be 3 or more, can be 4 or more. Specific examples of the halide solid electrolyte include Li3YBr6, Li3YCl6, or Li3YBr2C l4 ​​​​​​​​The thickness of the electrolyte layer may be, for example, 1 μm to 150 μm.

[0119] The electrolyte layer may further include an alkali metal salt, an ionic liquid, or a combination thereof.

[0120] The 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 can improve the ion conductivity by increasing the lithium ion mobility in the solid electrolyte layer.

[0121] Examples of the lithium salt include LiSCN, LiN(CN)2, Li(CF3SO2)3C, LiC4F9SO3, LiN(SO2CF2CF3)2, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), and lithium bis(fluorosulfonyl)imide (lithium bis(fluorosulfonyl)imide). The compound may include lithium bis(trifluoromethanesulfonyl)imide, LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide, LiFSI, LiN(SO2F)2), LiCF3SO3, LiAsF6, LiSbF6, LiClO4, or a mixture thereof.

[0122] In addition, the lithium salt may be an imide-based lithium salt, and examples of the imide-based lithium salt include lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiN(SOCF)), and lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SOF)). The lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0123] The ionic liquid has a melting point below room temperature and is a salt that is in a liquid state at room temperature and is composed only of ions, or a room-temperature molten salt.

[0124] The ionic liquid comprises: a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, 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 - The compound may contain one or more anions selected from the following:

[0125] The ionic liquid may be, for example, one or more selected from the group consisting of N-methyl-N-propylpyrrolidine 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.

[0126] The weight ratio of the solid electrolyte to the ionic liquid in the solid electrolyte layer 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.

[0127] The solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the resulting solution on a substrate film, and drying. The solvent for the binder solution can be isobutylyl isobutyrate, isolene, toluene, benzene, hexane, or a combination thereof. The process for forming the solid electrolyte layer is widely known in the art, and therefore, a detailed description thereof will be omitted here.

[0128] In one embodiment, a buffer material may be further included to buffer thickness changes that occur during charging and discharging of the all-solid-state battery. The buffer material may be located between the negative electrode and the case, and in the case of a battery in which one or more electrode assemblies are stacked, the buffer material may be located between different electrode assemblies.

[0129] The buffer material may be a material having an elastic recovery rate of 50% or more and having an insulating function, such as silicone rubber, acrylic rubber, fluorine-based rubber, nylon, synthetic rubber, or a combination thereof. The buffer material may be in the form of a polymer sheet.

[0130] FIG. 3 is a cross-sectional view of an all-solid-state battery according to an embodiment. Referring to FIG. 3, the all-solid-state battery 100 may have a structure in which an electrode assembly including a stack of an anode 400 including an anode current collector 401 and an anode layer 403, a solid electrolyte layer 300, and a cathode 200 including a cathode active material layer 203 and a cathode current collector 201 is housed in a case such as a pouch. The all-solid-state battery 100 may further include an elastic layer 500 on the outer surface of at least one of the cathode 200 and the anode 400. Although FIG. 3 shows one electrode assembly including the anode 400, the solid electrolyte layer 300, and the cathode 200, two or more electrode assemblies may be stacked to fabricate an all-solid-state battery.

[0131] 4 is a schematic diagram illustrating the structure of an all-solid-state battery according to another embodiment, for example, an all-solid-state battery in a charged state. The all-solid-state battery 100 includes a positive electrode 200 including a positive electrode current collector 201 and a positive electrode active material layer 203, a negative electrode current collector 401, a negative electrode 400′ including a negative electrode layer 403′, and a solid electrolyte 300 located between the positive electrode 200 and the negative electrode 400′, and a battery case 500 that houses these components.

[0132] Also, lithium ions are released from the positive electrode active material and deposited on the negative electrode current collector 401', resulting in a lithium deposit layer 405' being located between the current collector 401' and the negative electrode layer 403'. [Example]

[0133] Examples of the present invention and comparative examples are described below. These examples are merely examples of the present invention, and the present invention is not limited to these examples.

[0134] Example 1 (1) Manufacturing of the positive electrode LiNi 0.8 Co 0.1 Al 0.1A first region slurry was prepared by mixing O2 cathode active material, an azirodite-type first solid electrolyte Li6PS5Cl having an average particle size (D50) of 5 μm, a carbon nanotube conductive material, and a polyvinylidene fluoride binder in an isobutylyl isobutylate solvent, with the weight ratio of the cathode active material, first solid electrolyte, conductive material, and binder being 85:13.3:0.4:1.3.

[0135] LiNi 0.8 Co 0.1 Al 0.1 A second region slurry was prepared by mixing O2 cathode active material, an azirodite-type second solid electrolyte Li6PS5Cl having an average particle size (D50) of 1 μm, and a carbon nanotube conductive material in an octyl acetate solvent, with the weight ratio of the cathode active material, second solid electrolyte, conductive material, and binder being 85:13.3:0.4:1.3.

[0136] The second region slurry was coated on an aluminum current collector, dried and rolled at 60° C. to form a second region, and the first region slurry was coated on the second region, dried and rolled at 60° C. to form a first region, thereby fabricating a positive electrode for an all-solid-state battery. The thickness of the second region was 35 μm, and the thickness of the first region was 35 μm.

[0137] (2) Manufacturing of the negative electrode A negative electrode coating layer composition was prepared by mixing polyvinylidene fluoride binder, Ag nanoparticles (D50: 60 nm), and carbon black in an N-methylpyrrolidone solvent. The carbon black was a mixture of single particles with a particle size of 38 nm and secondary particles. The secondary particles were formed by assembling primary particles with a particle size of 76 nm, resulting in secondary particles with a particle size of 275 nm. The mixing ratio of the binder, Ag nanoparticles, and carbon black was 5:23.75:71.25 by weight.

[0138] The negative electrode coating composition was coated on a stainless steel foil current collector, and then vacuum dried at 100°C and rolled to prepare a negative electrode including a 7 μm-thick negative electrode coating layer and a 10 μm-thick current collector.

[0139] (3) Manufacturing of solid electrolyte layer The ajirodite-type solid electrolyte Li6PS5Cl was mixed with an isobutyryl isobutyrate binder (solid content: 50 wt%) containing butyl acrylate, an acrylate polymer. The mixing ratio of the solid electrolyte to the binder was 98.7:1.3 by weight.

[0140] The mixing process was carried out using a Thinky mixer. 2 mm zirconia balls were added to the resulting mixture, and the mixture was stirred again using the Thinky mixer to prepare a slurry. The slurry was cast onto a release polytetrafluoroethylene film and dried at room temperature to prepare a solid electrolyte layer with a thickness of 60 μm.

[0141] (3) Manufacturing of all-solid-state batteries The prepared negative electrode, solid electrolyte, and positive electrode were sequentially stacked, and a pressure of 2 Nm was applied to prepare an all-solid-state battery. The prepared battery had a positive electrode layer (excluding the current collector) thickness of 70 μm, a negative electrode layer (excluding the current collector) thickness of 7 μm, and a solid electrolyte layer thickness of 60 μm.

[0142] Example 2 A positive electrode was manufactured in the same manner as in Example 1, except that the first region slurry was prepared using an azirodite-type first solid electrolyte Li6PS5Cl having an average particle size (D50) of 3 μm.

[0143] An all-solid-state battery was manufactured using the positive electrode, the negative electrode manufactured in Example 1, and the solid electrolyte.

[0144] Example 3 A positive electrode was manufactured in the same manner as in Example 1, except that the second region slurry was prepared using an azirodite-type second solid electrolyte Li6PS5Cl having an average particle size (D50) of 3 μm.

[0145] An all-solid-state battery was manufactured using the positive electrode, the negative electrode manufactured in Example 1, and the solid electrolyte.

[0146] Example 4 A positive electrode was manufactured in the same manner as in Example 1, except that the first region slurry was prepared using an azirodite-type first solid electrolyte Li6PS5Cl having an average particle size (D50) of 10 μm.

[0147] An all-solid-state battery was manufactured using the positive electrode, the negative electrode manufactured in Example 1, and the solid electrolyte.

[0148] (Comparative Example 1) A first region slurry was prepared using an ajirodite-type first solid electrolyte Li6PS5Cl having an average particle size (D50) of 1 μm. A positive electrode was manufactured in the same manner as in Example 1, except that the second region slurry was prepared using an azirodite-type second solid electrolyte Li6PS5Cl having an average particle size (D50) of 5 μm.

[0149] An all-solid-state battery was manufactured using the positive electrode, the negative electrode manufactured in Example 1, and the solid electrolyte.

[0150] (Comparative Example 2) A positive electrode was manufactured in the same manner as in Comparative Example 1, except that the second region slurry was prepared using an azirodite-type second solid electrolyte Li6PS5Cl having an average particle size (D50) of 3 μm.

[0151] An all-solid-state battery was manufactured using the positive electrode, the negative electrode manufactured in Example 1, and the solid electrolyte.

[0152] (Comparative Example 3) LiNi 0.8 Co 0.1 Al0.1 A cathode layer slurry was prepared by mixing O2 cathode active material, an azirodite-type solid electrolyte Li6PS5Cl having an average particle size (D50) of 1 μm, a carbon nanotube conductive material, and a polyvinylidene fluoride binder in an isobutylyl isobutylate solvent, with the weight ratio of the cathode active material, solid electrolyte, conductive material, and binder being 85:13.3:0.4:1.3.

[0153] The positive electrode layer slurry was coated on an aluminum current collector, dried at 60° C., and rolled to prepare a positive electrode for an all-solid-state battery. The thickness of the positive electrode layer was 70 μm.

[0154] Comparative Example 4 A positive electrode for an all-solid-state battery was manufactured in the same manner as in Comparative Example 3, except that the positive electrode layer slurry was prepared using an azirodite-type solid electrolyte Li6PS5Cl having an average particle size (D50) of 5 μm.

[0155] An all-solid-state battery was manufactured using the positive electrode, the negative electrode manufactured in Example 1, and the solid electrolyte.

[0156] Example 5 LiNi 0.8 Co 0.1 Al 0.1 The second slurry for the third region was prepared by mixing O2 positive electrode active material, an ajirodite-type solid electrolyte Li6PS5Cl having an average particle size (D50) of 2 μm, and a carbon nanotube conductive material in an octyl acetate solvent, and the first slurry for the third region was prepared using an ajirodite-type solid electrolyte Li6PS5Cl having an average particle size of 3.5 μm. The mixing ratio of the positive electrode active material, solid electrolyte, conductive material, and binder in the final positive electrode was 85:13.3:0.4:1.3 by weight.

[0157] The second region slurry prepared in Example 1 was coated onto an aluminum current collector, followed by drying and rolling at 60°C to form the second region. The second region was then coated with the third region second slurry, dried at 60°C, and the third region first slurry was coated on top of the second region. The third region was then dried and rolled at 60°C to form the third region. The first region slurry prepared in Example 1 was then coated onto the aluminum current collector, followed by drying and rolling at 60°C to form the first region. A positive electrode for an all-solid-state battery was fabricated. The thickness of the second region was 20 μm, the thickness of the third region was 30 μm, and the thickness of the first region was 20 μm. The average particle size of the third solid electrolyte in the third region was 2.8 μm.

[0158] The positive electrode configurations of Examples 1 to 5 and Comparative Examples 1 to 4 are summarized in Table 1 below.

[0159] [Table 1]

[0160] Experimental Example 1) Evaluation of ionic and electronic conductivity The ionic conductivity and electronic conductivity of the positive electrodes prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were measured, and the results are shown in Table 2 below.

[0161] The ionic and electronic conductivities were measured by sampling the positive electrode with a 10mm diameter (10Φ) sample at room temperature (25°C) and applying a torque of 10 N m using an electric impedance spectroscopy (EPS) measuring device. The open circuit potential was set at 50mV and the frequency was scanned from 500kHz to 50mHz.

[0162] The results are shown in Table 2 below.

[0163] [Table 2]

[0164] As shown in Table 2 above, the electronic conductivities of Examples 1 to 5 are somewhat similar to those of Comparative Examples 1 to 4, but the ionic conductivities are significantly superior to those of Comparative Examples 1 to 4.

[0165] Although the preferred embodiment of the present invention has been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also fall within the scope of the present invention.

Claims

1. An all-solid-state battery, Negative electrode; an electrolyte layer; and a positive electrode including a positive electrode layer and a current collector supporting the positive electrode layer; the positive electrode layer includes a first region adjacent to the electrolyte layer and a second region adjacent to the current collector, the first region includes particles of a first solid electrolyte; the second region includes particles of a second solid electrolyte; an average particle size of the first solid electrolyte particles being larger than an average particle size of the second solid electrolyte particles;

2. 2. The all-solid-state battery according to claim 1, wherein a ratio of an average particle size of the second solid electrolyte particles to an average particle size of the first solid electrolyte particles is 1:1.1 to 40.

3. The all-solid-state battery according to claim 1 , wherein the positive electrode layer comprises the first region and the second region.

4. The all-solid-state battery according to claim 3 , wherein the first region has a thickness corresponding to 70% or less of the total thickness of the positive electrode layer.

5. The all-solid-state battery according to claim 3 , wherein the second region has a thickness corresponding to 30% or more of the total thickness of the positive electrode layer.

6. the first solid electrolyte particles include large solid electrolyte particles and small solid electrolyte particles, 4. The all-solid-state battery according to claim 3, wherein the particles of the second solid electrolyte include small particles of a solid electrolyte.

7. the first solid electrolyte particles are large solid electrolyte particles and small solid electrolyte particles, 4. The all-solid-state battery according to claim 3, wherein the particles of the second solid electrolyte are small particles of a solid electrolyte.

8. 7. The all-solid-state battery according to claim 6, wherein an average particle size ratio of the large particles of the solid electrolyte to the small particles of the solid electrolyte is 1.5:1 to 40:

1.

9. 7. The all-solid-state battery according to claim 6, wherein the large particles of the solid electrolyte have an average particle size of 1 μm to 20 μm.

10. 7. The all-solid-state battery according to claim 6, wherein the small particles of the solid electrolyte have an average particle size of 0.1 μm to 5 μm.

11. 2. The all-solid-state battery according to claim 1, wherein a thickness ratio of the first region and the second region is 70:30 to 30:

70.

12. The all-solid-state battery according to claim 1 , wherein the positive electrode layer includes a third region between the first region and the second region.

13. 13. The all-solid-state battery according to claim 12, wherein the first region corresponds to a thickness of 24% or more and 56% or less of a total thickness (100%) of the positive electrode layer, and the second region corresponds to a thickness of 24% or more and 56% or less of a total thickness (100%) of the positive electrode layer.

14. The all-solid-state battery according to claim 12 , wherein the third region corresponds to 20% to 50% of the total thickness of the positive electrode layer.

15. 13. The all-solid-state battery according to claim 12, wherein the third region includes particles of a third solid electrolyte, and the particles of the third solid electrolyte have an average particle size that increases in a direction from a second surface in contact with the second region to a first surface in contact with the first region.

16. 16. The all-solid-state battery according to claim 15, wherein the average particle size of the particles of the third solid electrolyte on the second surface is 0.1 μm to 5 μm, and the average particle size of the particles of the third solid electrolyte on the first surface is 1 μm to 20 μm.

17. the third region includes particles of a third solid electrolyte; a particle size ratio of the first solid electrolyte particles in the first region to the particle size of the second solid electrolyte particles in the second region is 1.1 / 1 or more and less than 5 / 1; 13. The all-solid-state battery according to claim 12, wherein, when a second surface in contact with the second region is taken as 0% and a first surface in contact with the first region is taken as 100%, in the third region, an average particle size of the third solid electrolyte increases by 1% to 40% at a position where the particle size increases by 10% in a thickness direction from the second surface to the first surface of the positive electrode layer.

18. the third region includes particles of a third solid electrolyte; a particle size ratio of the first solid electrolyte particles in the first region to the particle size of the second solid electrolyte particles in the second region is 5 / 1 or more and 40 / 1 or less; 13. The all-solid-state battery according to claim 12, wherein, when a second surface in contact with the second region is defined as 0% and a first surface in contact with the first region is defined as 100%, an average particle size of the particles of the third solid electrolyte increases by 40 to 390% for every 10% increase in the thickness direction of the positive electrode layer.

19. 13. The all-solid-state battery according to claim 12, wherein the third region is divided into two to five zones in a thickness direction, and the average particle size of the particles of the third solid electrolyte in each zone is different from each other.

20. 13. The all-solid-state battery according to claim 12, wherein the third region is divided into two to five sections in a thickness direction, a section in contact with the first region is a first section, a section in contact with the second region is an n section, and an average particle size of the third solid electrolyte particles increases from the n section toward the first section.

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