All-solid-state battery

Abstract

The present invention relates to an all-solid-state battery comprising: a negative electrode; an electrolyte layer; and a positive electrode including a positive electrode layer and a current collector supporting the positive electrode layer, in which the positive electrode layer includes a first region adjacent to the electrolyte layer and a second region adjacent to the positive electrode current collector, the first region including first solid electrolyte particles and the second region including second solid electrolyte particles, and the average particle size of the first solid electrolyte particles is greater than the average particle size of the second solid electrolyte particles.

Description

Technical Field

[0001] All-solid-state batteries are disclosed. Background Art

[0002] Recently, the rapid replenishment of electronic devices (such as mobile phones, laptop computers) using batteries and electric vehicles has led to an astonishing increase in the demand for rechargeable batteries with relatively high capacity and lighter weight. In particular, rechargeable lithium batteries have recently attracted attention as a driving power source for portable devices because of their lighter weight and high energy density. Accordingly, research and development to improve the performance of rechargeable lithium batteries are actively underway.

[0003] An all-solid-state battery in a rechargeable lithium battery refers to a battery in which all materials are solid, and particularly a battery using a solid electrolyte. These all-solid-state batteries have excellent safety because there is no risk of electrolyte leakage, and they have the advantage of being easy to manufacture thin batteries.

[0004] In these all-solid-state batteries, ion transport occurs through physical contact between the positive electrode or the negative electrode and the solid electrolyte. Therefore, the contact area between the positive electrode or the negative electrode and the solid electrolyte is important. To increase this contact area, methods of reducing the particle size of the solid electrolyte particles have been studied, but in this case, there is a problem of an increase in interface resistance, resulting in a decrease in the fast charge / discharge performance of the battery. Summary of the Invention

[0005] Technical Problem

[0006] Embodiments provide all-solid-state batteries having excellent fast charge / discharge performance and capacity.

[0007] Technical Solution

[0008] Embodiments provide an 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, wherein 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 first solid electrolyte particles, the second region includes second solid electrolyte particles, and the average particle size of the first solid electrolyte particles is larger than the average particle size of the second solid electrolyte particles.

[0009] 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.

[0010] The positive electrode layer may be composed of the first region and the second region.

[0011] The first region may correspond to a thickness that is less than or equal to 70% of the total thickness of the positive electrode layer. Additionally, the second region may correspond to a thickness that is greater than or equal to 30% of the total thickness of the positive electrode layer.

[0012] 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 an 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.

[0013] The average particle size ratio of the small solid electrolyte particles to the large solid electrolyte particles may be from 1:1.5 to 1:40.

[0014] The average particle size of the above-mentioned large solid electrolyte particles may be from 1 μm to 20 μm. The average particle size of the small solid electrolyte particles may be from 0.1 μm to 5 μm.

[0015] The thickness ratio of the first region to the second region may be from 70:30 to 30:70.

[0016] The positive electrode layer may include a third region between the first region and the second region. The third region may include third solid electrolyte particles, and the third solid electrolyte particles 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. Herein, based on 100% of the total thickness of the positive electrode layer, the first region may correspond to a thickness that is less than or equal to 56% and greater than or equal to 24%, and based on 100% of the total thickness of the positive electrode layer, the second region may correspond to a thickness that is greater than or equal to 24% and less than or equal to 56%. Additionally, the third region may correspond to 20% - 50% of the total thickness of the positive electrode layer.

[0017] The average particle size of the third solid electrolyte particles on the second surface may be from 0.1 μm to 5 μm, and the average particle size of the third solid electrolyte particles on the first surface may be from 1 μm to 20 μm.

[0018] The particle size ratio of the particle size 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 greater than or equal to 1.1 / 1 and less than 5 / 1, and when the second surface in contact with the second region is set to 0% and the first surface in contact with the first region is set to 100%, then at a position 10% increased in the thickness direction from the second surface to the first surface of the positive electrode layer, the average particle size of the third solid electrolyte in the third region increases by 1% - 40%.

[0019] 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 greater than or equal to 5 / 1 and less than or equal to 40 / 1, and when the second surface in contact with the second region is set to 0% and the first surface in contact with the first region is set to 100%, then in the third region, at a position 10% increased in the thickness direction from the second surface to the first surface of the positive electrode layer, the average particle size of the third solid electrolyte increases by 40% to 390%.

[0020] The third region can be divided into two to five zones in the thickness direction, and the average particle size of the third solid electrolyte particles in each zone can be different.

[0021] The third region can be divided into two to five zones in the thickness direction. The zone in contact with the first region can be the first zone, and the zone in contact with the second region can be the nth zone. And in the nth zone, the average particle size of the third solid electrolyte particles can increase in the direction of the first zone.

[0022] Advantageous Effects

[0023] The all-solid-state battery according to the embodiment can improve the fast charge / discharge performance and capacity of the battery. Description of the Drawings

[0024] Figure 1 It is a cross-sectional view schematically illustrating a positive electrode of an all-solid-state battery according to an embodiment.

[0025] Figure 2 It is a cross-sectional view schematically showing a positive electrode of an all-solid-state battery according to another embodiment.

[0026] Figure 3 It is a cross-sectional view schematically illustrating an all-solid-state battery according to an embodiment.

[0027] Figure 4 It is a cross-sectional view schematically illustrating an all-solid-state battery according to another embodiment. Detailed Description of the Embodiments

[0028] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are merely examples, and the present invention is not limited thereto, and the present invention is defined by the scope of the claims.

[0029] As used herein, when not otherwise specifically limited, it will be understood that when an element (such as a layer, film, region, or substrate) is referred to as being "on" another element, it can be directly on the other element, or there can also be intervening elements.

[0030] In the present invention, the "particle size" or "grain size" may be an average particle size. Additionally, the average particle size may be defined as the average particle size (D 50 ) based on a cumulative volume of 50% in the cumulative size distribution curve. The grain size can be measured, for example, by electron microscopy using a scanning electron microscope (SEM) or a field emission scanning electron microscope (FE-SEM), or by a laser diffraction method. It can be measured by the following laser diffraction method. The particles to be measured are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 of Microtrac Inc.). Ultrasonic waves of approximately 28 kHz are irradiated at an output power of approximately 60 W, and the average particle size (D 50 ) based on 50% of the particle size distribution in the measuring device can be calculated.

[0031] The all-solid-state battery according to an embodiment includes a negative electrode, an electrolyte layer, and a positive electrode. The positive electrode includes a positive electrode layer and a current collector supporting the positive electrode layer, and the positive electrode layer includes a first region adjacent to the electrolyte layer and a second region adjacent to the positive electrode current collector. In the embodiment, the first region includes first solid electrolyte particles, the second region includes second solid electrolyte particles, and the average particle size of the first solid electrolyte particles may be greater than the average particle size of the second solid electrolyte particles.

[0032] The all-solid-state battery may also be referred to as an all-solid-state rechargeable battery or an all-solid-state rechargeable lithium battery.

[0033] 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.

[0034] Thus, by including first solid electrolyte particles having a large average particle size in the first region adjacent to the electrolyte layer, the lithium ion conductivity can be increased, thereby improving the fast charge / discharge characteristics and the cycle life characteristics. Additionally, the second region adjacent to the current collector may include second solid electrolyte particles having a small average particle size to increase the contact area with the positive electrode active material, thereby increasing the capacity. Additionally, since second solid electrolyte particles having a small average particle size are included in the second region adjacent to the current collector, the ion transport path can be increased.

[0035] Thus, if 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, the effects of using solid electrolyte particles having different average particle sizes according to the position of the positive electrode layer can be obtained more effectively.

[0036] According to an embodiment, the positive electrode may be such that the positive electrode layer is composed of a first region and a second region. That is, the positive electrode layer may be divided into two regions. Refer to Figure 1 , the 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) and a second region 5b adjacent to the current collector 3. In addition, the average particle size of the first solid electrolyte particles included in the first region 5a may be larger than the average particle size of the second solid electrolyte particles included in the second region 5b. In Figure 1 , only the first solid electrolyte particles and the second solid electrolyte particles are shown in the first region 5a and the second region 5b, and particles other than the solid electrolyte particles are omitted.

[0037] In an embodiment, the first region represents a region corresponding to less than or equal to 70% of the total thickness of the positive electrode layer, that is, Figure 1 , the term a shown in Figure 1 represents a region corresponding to less than or equal to 70% of the total thickness (h) of the positive electrode layer. In addition, the second region represents a region corresponding to greater than or equal to 30% of the total thickness of the positive electrode layer, that is,

[0038] the term b shown in

[0039] represents a region corresponding to greater than or equal to 30% of the total thickness (h) of the positive electrode layer.

[0040] Thus, if the positive electrode layer is composed of a first region and a 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. To explain this in more detail, the first solid electrolyte particles in the first region may include solid electrolytes having different particle sizes (for example, large solid electrolyte particle sizes and small solid electrolyte particle sizes), and the second solid electrolyte particles in the second region may include only particles having substantially uniform sizes, that is, small particle sizes.

[0041] In an embodiment, the average particle size of the large solid electrolyte particles may be 1 μm to 20 μm, and may also be 1 μm to 10 μm, 1.5 μm to 10 μm, or 2 μm to 5 μm. Additionally, the average particle size of the small solid electrolyte particles may be 0.1 μm to 5 μm, 0.5 μm to 4 μm, or 0.5 μm to 3 μm. If the average particle size of the large solid electrolyte particles is within the above range, the grain boundary resistance can be further reduced, thereby further improving the conductivity. Additionally, if the average particle size of the small solid electrolyte particles is within the above range, it can have the advantage of reducing the porosity of the positive electrode.

[0042] The thickness ratio of the first region and the second region may be 70:30 to 30:70. If the thickness ratio of the first region and the second region falls within the above range, the ionic resistance of the positive electrode can be further reduced.

[0043] The positive electrode layer including the first region and the second region can be formed by coating a second positive electrode layer composition including second solid electrolyte particles on a current collector and drying it, and then coating first solid electrolyte particles and drying them.

[0044] According to another embodiment, the positive electrode layer may further include a third region between the first region and the second region. As Figure 2 shown, this structure includes a positive electrode 1' including a current collector 3' and a positive electrode layer 5', 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' between the first region 5a' and the second region 5b'.

[0045] If 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.

[0046] Herein, based on 100% of the total thickness of the positive electrode layer, the first region may correspond to a thickness of less than or equal to 56% and greater than or equal to 24%, and based on 100% of the total thickness of the positive electrode layer, the second region may correspond to a thickness of greater than or equal to 24% and less than or equal to 56%. That is, the thickness (a') corresponding to the first region shown in Figure 2 may be less than or equal to 56% of the total thickness (h) of the positive electrode layer and greater than or equal to 24% of the total thickness (h) of the positive electrode layer, and the thickness (b') corresponding to the second region may be greater than or equal to 24% of the total thickness (h) of the positive electrode layer and less than or equal to 56% of the total thickness (h) of the positive electrode layer.

[0047] The configuration of the average particle sizes of the first solid electrolyte particles and the second solid electrolyte particles included in the first region and the second region is as described above.

[0048] 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 and may also increase step by step.

[0049] If the average particle size increases gradually, the third solid electrolyte particles 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. The second surface in contact with the second region may be set to 0%, and the first surface in contact with the first region may be set to 100% so that a gradient can be generated from the second surface toward the first surface.

[0050] If the gradient of the average particle size of the third solid electrolyte particles increases gradually, the gradient can be appropriately controlled according to 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, if 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 greater than or equal to 1.1 / 1 and less than 5 / 1, at a position where the thickness increases by 10% in the thickness direction from the second surface to the first surface, the particle size of the third solid electrolyte particles can increase by 1% to 40%. At this time, the increased particle size value means 1% to 40% of the initial particle size, that is, 1% to 40% of the particle size value of the third solid electrolyte particles on the second surface. For example, if the particle size of the third solid electrolyte particles on the second surface is 0.1 μm, the particle size of the third solid electrolyte particles can be 0.101 μm to 0.14 μm at a position where the thickness increases by 10% in the thickness direction, and can be 0.102 μm to 0.18 μm at a position where the thickness increases by 20% in the thickness direction.

[0051] According to another embodiment, if 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 greater than or equal to 5 / 1 and less than or equal to 40 / 1, in the third region, at a position where the thickness increases by 10% in the thickness direction from the second surface of the positive electrode layer to the first surface, the average particle size of the third solid electrolyte can increase by 40% to 390%. At this time, the increased particle size value means that it is 40% to 390% of the initial particle size, that is, 40% to 390% of the particle size value of the third solid electrolyte particles on the second surface. For example, if the particle size of the third solid electrolyte particles on the second surface is 1 μm, the particle size of the third solid electrolyte particles can be 4.9 μm at a position where the thickness increases by 10% in the thickness direction, and can be 8.8 μm at a position where the thickness increases by 20% in the thickness direction.

[0052] In the third region, if the average particle size of the solid electrolyte particles increases from the second surface to the first surface, the ionic resistance of the positive electrode can be further reduced. In particular, if the conditions are met and increased, the ionic resistance of the positive electrode can be reduced more effectively.

[0053] If the solid electrolyte particles in the third region gradually increase from the second surface toward the first surface, the third region is divided into two to five zones, and the average particle size of the solid electrolyte particles in each zone can be different from each other. In this regard, for the sake of explanation, the third region is divided into two to five zones in the thickness direction, and if the zone in contact with the first region is called the first zone, and the one in contact with the second region is called the nth zone, then in the nth zone, the average particle size of the solid electrolyte particles can increase in the direction of the first zone.

[0054] The average particle size of the third solid electrolyte particles on the second surface can be 0.1 μm to 5 μm, and the average particle size of the third solid electrolyte particles on the first surface can be 1 μm to 20 μm.

[0055] If 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 pores can be further reduced, and the ionic resistance can be further reduced.

[0056] The gradual increase in the average particle size of the solid electrolyte particles in the third region can be achieved by performing the process of coating the composition for forming the positive electrode layer on the current collector multiple times, and at this time, the average particle size of the solid electrolyte particles included in the composition is made different. That is, the solid electrolyte particles included in the composition directly coated on the current collector for forming the positive electrode layer have a small average particle size, and if coated multiple times (i.e., as the number of coating times increases), the average particle size of the solid electrolyte particles will also increase and can be formed.

[0057] For each increase in the number of coating times, the average particle size of the solid electrolyte particles can increase by 2% to 780% of the initial average particle size of the solid electrolyte particles. Accordingly, the average particle size of the solid electrolyte particles on the second surface in contact with the second region can be formed to be 0.1 μm to 5 μm, and finally, the average particle size of the solid electrolyte particles in the nth zone in contact with the first region in contact with the electrolyte layer can be formed to be 1 μm to 20 μm.

[0058] The solid electrolyte can be a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

[0059] Sulfide-based solid electrolytes can be, for example, Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen, e.g., 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 (where m and n are integers respectively, and Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are integers, and M is P, Si, Ge, B, Al, Ga or In), etc.

[0060] Sulfide-based solid electrolytes 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. Within the above mixing ratio range, sulfide-based solid electrolytes with excellent ionic conductivity can be prepared. By adding SiS2, GeS2, B2S3, etc. as other components thereto, the ionic conductivity can be further improved. Mechanical grinding or solution method can be applied as the mixing method. Mechanical grinding is to make the raw materials into fine particles by putting the raw materials, ball mill, etc. into a reactor and stirring vigorously. The solution method can be carried out by mixing the raw materials in a solvent to obtain a solid electrolyte as a precipitate. In addition, additional firing can be carried out after mixing. If additional firing is carried out, the crystals of the solid electrolyte can become stronger.

[0061] For example, the solid electrolyte can be a thio-LISICON type sulfide-based solid electrolyte. Sulfide-based solid electrolytes can be, for example, Li a M b P c S d A e (where a, b, c, d and e are all 0 or greater and 12 or less, M is Ge, Sn, Si or a combination thereof, and A is one of F, Cl, Br or I), and specifically, can be Li3PS4, Li7P3S 11 , Li6PS5Cl, Li6PS5Br, Li6PS5I, etc.

[0062] The sulfide-based solid electrolyte can be an amorphous sulfide-based solid electrolyte or a crystalline sulfide-based solid electrolyte, or can be a mixture of both. Of course, a commercially available solid electrolyte can be used as the sulfide-based solid electrolyte.

[0063] The oxide-based inorganic solid electrolyte can 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 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 3-y O 12 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1), lanthanum lithium titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2-based ceramics, garnet ceramics Li 3+ x La3M2O 12 (M = Te, Nb or Zr; and x is an integer from 1 to 10) or a mixture thereof.

[0064] The solid electrolyte can be in the form of particles, and the average particle size (D 50) may be less than or equal to 5.0 μm, for example, 0.1 μm to 5.0 μm, 0.5 μm to 5.0 μm, 0.5 μm to 4.0 μm, 0.5 μm to 3.0 μm, 0.5 μm to 2.0 μm, or 0.5 μm to 1.0 μm. These solid electrolytes can effectively penetrate between the positive electrode active materials and have excellent contact with the positive electrode active materials and connectivity between the solid electrolyte particles.

[0065] In an embodiment, the first solid electrolyte particles, the second solid electrolyte particles, and the third solid electrolyte particles may be the same as or different from each other.

[0066] In the positive electrode layer, based on the total weight of the positive electrode layer, the total amount of the first solid electrolyte particles, the second solid electrolyte particles, and the third solid electrolyte particles 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%. Additionally, based on the total weight of the positive electrode active material and the solid electrolyte, the positive electrode layer may include 65 wt% to 99 wt% of the positive electrode active material and 1 wt% to 35 wt% of the solid electrolyte, for example, 80 wt% to 90 wt% of the positive electrode active material and 10 wt% to 20 wt% of the solid electrolyte. If the solid electrolyte is included in such an amount in the positive electrode, the efficiency and cycle life characteristics of the all-solid-state battery can be improved without reducing the capacity.

[0067] It is only necessary to control the total amount of the solid electrolyte particles included in the positive electrode layer, and there is no need to control the amount of the solid electrolyte particles included in each region.

[0068] The positive electrode layer includes a positive electrode active material.

[0069] The positive electrode active material may be a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. For example, the positive electrode active material may be at least one of composite oxides of lithium and metals selected from cobalt, manganese, nickel, and combinations thereof. Examples of the positive electrode active material may 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 1b O 4-c D 1 c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5); 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 Mn 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 Mn 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 Mn 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 E c G dO2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); 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 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.

[0070] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof; B 1 is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D 1 is O, F, S, P, or a combination thereof; 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; and L 1 is Mn, Al, or a combination thereof.

[0071] According to an embodiment, the positive electrode active material can be a ternary lithium transition metal, such as LiNi x Co y Al z O2 (NCA), LiNi x Co y Mn zO2(NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1).

[0072] Also, the compound may have a coating on its surface or may be mixed with another compound having a coating. The coating may include at least one coated element compound selected from oxides of the coated element, hydroxides of the coated element, hydroxyoxides of the coated element, oxycarbonates of the coated element, and hydroxycarbonates of the coated element. The compound used for the coating may be amorphous or crystalline. The coated elements included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating can be provided by using these elements in the compound in a manner that has no adverse effect on the properties of the positive electrode active material. For example, the method may include any coating method (such as spraying, dipping, etc.), but since it is well known in the relevant art, it is not explained in more detail.

[0073] In addition, as the coating, any known coating for the positive electrode active material of an all-solid-state battery can be applied, examples of which include Li2O-ZrO2 (LZO).

[0074] Here, examples of the shape of the positive electrode active material include particulate shapes (such as spheres and ellipsoids). In addition, the average particle size of the positive electrode active material is not particularly limited and can be within the range applicable to the positive electrode active material of existing all-solid-state rechargeable batteries. In addition, the amount of the positive electrode active material in the positive electrode active material layer is not particularly limited and can be within the range applicable to the positive electrode layer of existing all-solid-state rechargeable batteries.

[0075] In an embodiment, based on the total weight of the positive electrode layer, the content of the positive electrode active material may be 55 wt% to 99.7 wt% (for example, 74 wt% to 89.8 wt%). If the content is within the above range, the capacity of the all-solid-state battery can be maximized while improving the cycle life characteristics.

[0076] The positive electrode layer may further include a conductive material. The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used. The conductive material may include, for example: carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, or carbon nanotube; metallic materials including copper, nickel, aluminum, or silver in the form of metal powder or metal fiber; conductive polymers such as poly(phenylene) derivatives; or a mixture thereof.

[0077] Based on the total weight of each component of the positive electrode for all-solid-state batteries or based on the total weight of the positive electrode layer, the content of the conductive material can be 0.1 wt% to 5 wt% or 0.1 wt% to 3 wt%. Within the above-mentioned amount range, the conductive material can improve the conductivity without degrading the battery performance.

[0078] The current collector may include, 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 a thin sheet.

[0079] The negative electrode includes a current collector and a negative electrode layer on one surface of the current collector.

[0080] The negative electrode layer may be a negative electrode active material layer or a negative electrode coating. Optionally, the negative electrode layer may be a lithium metal layer.

[0081] 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.

[0082] The negative electrode active material may include a material that reversibly inserts / extracts lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0083] The material that reversibly inserts / extracts lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be of an unspecified shape, or natural graphite or artificial graphite in the form of flakes, lamellae, spheres, or fibers, and the amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0084] The lithium metal alloy includes 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.

[0085] The material capable of doping / dedoping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiO x(0 < x < 2), Si-Q alloy (where Q is an element selected from 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 is not Si), and the Sn-based negative electrode active material can be Sn, SnO2, Sn-R alloy (where R is an element selected from 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 is not Sn), etc. At least one of these materials can be mixed with SiO2. The element Q and the element R can be selected from 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.

[0086] The silicon-carbon composite can be, for example, a silicon-carbon composite including a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The crystalline carbon can be artificial graphite, natural graphite, or a combination thereof. The above amorphous carbon precursor can be coal tar pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin (such as phenolic resin, furan resin, or polyimide resin). In this case, based on the total weight of the silicon-carbon composite, the amount of silicon can be 10 wt% to 50 wt%. Additionally, based on the total weight of the silicon-carbon composite, the amount of crystalline carbon can be 10 wt% to 70 wt%, and based on the total weight of the silicon-carbon composite, the amount of amorphous carbon can be 20 wt% to 40 wt%. Additionally, the thickness of the amorphous carbon coating can be 5 nm to 100 nm.

[0087] The average particle size (D 50 ) of the silicon particles can be 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles can exist in an oxidized form, and in this case, the atomic weight ratio of Si:O indicating the degree of oxidation in the silicon particles can be a weight ratio of 99:1 to 33:67. The silicon particles can be SiO x particles, where the range of x in SiO x can be greater than 0 and less than 2. Here, the average particle size (D 50 ) is measured by a particle size analyzer using laser diffraction and means the diameter of the particles having a cumulative 50 volume% in the particle size distribution.

[0088] Si-based negative electrode active material or Sn-based negative electrode active material can be mixed with carbon-based negative electrode active material. If the Si-based negative electrode active material or Sn-based negative electrode active material is mixed and used with the carbon-based negative electrode active material, the mixing ratio can be a weight ratio of 1:99 to 90:10.

[0089] In the negative electrode active material layer, based on the total weight of the negative electrode active material layer, the amount of the included negative electrode active material can be 95 wt% to 99 wt%.

[0090] In an embodiment, the negative electrode active material layer further includes a binder, and optionally may further include a conductive material. Based on the total weight of the negative electrode active material layer, the amount of the binder in the negative electrode active material layer can be 1 wt% to 5 wt%. Additionally, if a conductive material is further included, the negative electrode active material layer can 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.

[0091] The binder is used to bond the negative electrode active material particles well to each other and also bond the negative electrode active material to the current collector. The binder can include a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0092] The water-insoluble binder can 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.

[0093] The water-soluble binder can include a rubber-based binder or a polymer resin binder. The rubber binder can be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and a combination thereof. The polymer resin binder can 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 a combination thereof.

[0094] If a water-soluble binder is used as the above-mentioned negative electrode binder, a thickener capable of imparting viscosity can be used together, and the thickener can include, for example, a cellulose-based compound. The cellulose-based compound can include carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, its alkali metal salts, or a combination thereof. The alkali metal can be Na, K, or Li. Based on 100 parts by weight of the negative electrode active material, the amount of such a thickener used can be 0.1 part by weight to 3 parts by weight. The cellulose-based compound can also act as a binder.

[0095] The binder is not limited thereto, and any binder used in the relevant technical field may be used, and the amount of the binder may also be appropriately adjusted.

[0096] The conductive material is used to provide conductivity to the electrode and may include, for example: carbon materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and carbon nanotube; metal 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.

[0097] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metal, and combinations thereof.

[0098] If the negative electrode layer is a negative electrode coating, it means that the negative electrode is a deposition type negative electrode. The deposition type negative electrode means that the negative electrode active material is not included during battery assembly, but lithium metal etc. precipitates therein during battery charging, and it acts as the negative electrode active material. To explain this in more detail, if a all-solid-state battery is charged, lithium ions are deintercalated from the positive electrode active material, pass through the solid electrolyte, and move towards the negative electrode, and precipitate on the negative electrode current collector, resulting in the formation of a lithium precipitation layer between the current collector and the negative electrode coating. The negative electrode having such a lithium precipitation layer is called a deposition type negative electrode.

[0099] That is, a lithium precipitation layer may be formed between the negative electrode current collector and the negative electrode layer.

[0100] The charging process may be a formation process carried out at about 25 °C to 50 °C at 0.05C to 1C for 1 to 3 times.

[0101] The thickness of the lithium precipitation layer may be 10 μm to 50 μm. For example, the thickness of the lithium precipitation layer may be greater than or equal to 10 μm, greater than or equal to 20 μm, greater than or equal to 30 μm, or greater than or equal to 40 μm and less than or equal to 50 μm, less than or equal to 40 μm, less than or equal to 30 μm, or less than or equal to 20 μm. If the thickness of the lithium precipitation layer is within the above range, there may be an advantage that lithium can precipitate reversibly during the charge / discharge process, thereby further improving the cycle life.

[0102] The negative electrode coating may include a metal, a carbon material, or a combination thereof that acts as a catalyst. In the negative electrode coating, for example, the metal may be loaded on the carbon material, or the metal and the carbon material may exist as a mixture. In an embodiment, the negative electrode coating may include a metal and a carbon material.

[0103] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof, and may be amorphous carbon. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microspheres, or a combination thereof. The amorphous carbon may be, for example, carbon black, acetylene black, super conductive acetylene carbon 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 thereto, and of course any substance classified as amorphous carbon in the relevant field can be used.

[0104] The amorphous carbon may be a single particle, may have the form of secondary particles in which a plurality of primary particles are aggregated, or may be a combination of these.

[0105] The particle size of the above single particle may be 10 nm to 60 mm. In addition, the particle size of the primary particle may be 20 nm to 100 nm, and the particle size of the secondary particle may be 1 μm to 20 μm.

[0106] In an embodiment, the particle size of the primary particle may be greater than or equal to 20 nm, greater than or equal to 30 nm, greater than or equal to 40 nm, greater than or equal to 50 nm, greater than or equal to 60 nm, greater than or equal to 70 nm, greater than or equal to 80 nm, or greater than or equal to 90 nm, and less than or equal to 100 nm, less than or equal to 90 nm, less than or equal to 80 nm, less than or equal to 70 nm, less than or equal to 60 nm, less than or equal to 50 nm, less than or equal to 40 nm, or less than or equal to 30 nm.

[0107] In an embodiment, the particle size of the secondary particle may be greater than or equal to 1 μm, greater than or equal to 3 μm, greater than or equal to 5 μm, greater than or equal to 7 μm, greater than or equal to 10 μm, or greater than or equal to 15 μm, and less than or equal to 20 μm, less than or equal to 15 μm, less than or equal to 10 μm, less than or equal to 7 μm, less than or equal to 5 μm, or less than or equal to 3 μm.

[0108] The shape of the primary particle may be spherical, ellipsoidal, plate-like, and combinations thereof, and in an embodiment, the shape of the primary particle may be spherical, ellipsoidal, and combinations thereof.

[0109] 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 may be Ag in an embodiment. If the negative electrode coating includes the above metal, the conductivity of the negative electrode can be improved.

[0110] 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 greater than or equal to 5 nm, greater than or equal to 50 nm, greater than or equal to 100 nm, greater than or equal to 150 nm, greater than or equal to 200 nm, greater than or equal to 250 nm, greater than or equal to 300 nm, greater than or equal to 350 nm, greater than or equal to 400 nm, greater than or equal to 450 nm, greater than or equal to 500 nm, greater than or equal to 550 nm, greater than or equal to 600 nm, greater than or equal to 650 nm, greater than or equal to 700 nm, or greater than or equal to 750 nm. Additionally, the size of the metal particles may be less than or equal to 800 nm, less than or equal to 750 nm, less than or equal to 700 nm, less than or equal to 650 nm, less than or equal to 600 nm, less than or equal to 550 nm, less than or equal to 500 nm, less than or equal to 450 nm, less than or equal to 400 nm, less than or equal to 350 nm, or less than or equal to 300 nm, and less than or equal to 250 nm, less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, or less than or equal to 50 nm. If the size of the metal particles is within the above range, the battery characteristics (e.g., cycle life characteristics) of the all-solid-state battery can be improved.

[0111] If the negative electrode coating includes a carbonaceous material and metal particles, the mixing ratio of the carbonaceous material and the metal particles can be a weight ratio of 1:1 to 99:1. For example, the weight of the carbonaceous material relative to the metal particles can be greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 10, greater than or equal to 15, greater than or equal to 20, greater than or equal to 25, greater than or equal to 30, greater than or equal to 35, greater than or equal to 40, greater than or equal to 45, greater than or equal to 50, greater than or equal to 55, greater than or equal to 60, greater than or equal to 65, greater than or equal to 70, greater than or equal to 75, greater than or equal to 80, greater than or equal to 85, greater than or equal to 90 or greater than or equal to 95, and less than or equal to 99, less than or equal to 95, less than or equal to 90, less than or equal to 85, less than or equal to 80, less than or equal to 75, less than or equal to 70, less than or equal to 65, less than or equal to 60, less than or equal to 55, less than or equal to 50, less than or equal to 45, less than or equal to 40, less than or equal to 35, less than or equal to 30, less than or equal to 25, less than or equal to 20, less than or equal to 15, less than or equal to 10, less than or equal to 5, less than or equal to 4, less than or equal to 3 or less than or equal to 2. For example, the weight ratio of the carbonaceous material to the metal particles can 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. If the carbonaceous material and the metal particles are included in the above weight ratio, the conductivity of the negative electrode can be further improved.

[0112] In addition, the negative electrode coating can further include a binder, a conductive material, and / or a solid electrolyte.

[0113] The binder and the conductive material are the same as the binder and the conductive material described in the negative electrode active material layer.

[0114] The solid electrolyte can be a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof used for the positive electrode as described above. The solid electrolyte included in the negative electrode can be the same as or different from the solid electrolyte included in the positive electrode.

[0115] The negative electrode layer can further include additives (such as fillers, dispersants, and ion conductive materials). In addition, known materials commonly used in all-solid-state batteries can be used as fillers, dispersants, ion conductive materials, etc. that can be included in the negative electrode layer.

[0116] The thickness of the negative electrode coating can be 1 μm to 15 μm or 5 μm to 10 μm.

[0117] The current collector may include, 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 a thin 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.

[0118] The electrolyte layer may include a solid electrolyte. The solid electrolyte may be an inorganic solid electrolyte (such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte) or a solid polymer electrolyte.

[0119] 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 included in the positive electrode or the negative electrode.

[0120] The solid polymer electrolyte may include, for example, those selected from polyethylene oxide, poly(diallyldimethylammonium) trifluoromethanesulfonimide (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 、Na5TiP3O 12 、Na3Fe2P3O 12 、Na4NbP3O 12 、sodium silicate, Li 0.3 La 0.5 TiO3, Na5MSi4O 12 (where M is a rare earth element such as Nd, Gd, Dy, etc.), Li5ZrP3O 12 、Li5TiP3O 12 、Li3Fe2P3O 12 、Li4NbP3O 12 、Li 1+x (M,Al,Ga) x (Ge 1-y Ti y ) 2-x(PO4)3 (where x ≤ 0.8, 0 ≤ y ≤ 1.0, and 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, and Q is Al or Ga), Li6BaLa2Ta2O 12 、Li7La3Zr2O 12 、Li5La3Nb2O 12 、Li5La3M2O 12 (M is Nb or Ta) and Li 7+x A x La 3-x Zr2O 12 (0 < x < 3, A is Zn), one or more of them.

[0121] The halide-based solid electrolyte may include Li element, M element (M is a metal other than Li), and X element (X is a halogen). Examples of X may include F, Cl, Br, and I. In particular, in the halide-based solid electrolyte, at least one of Br and Cl is suitable as the above X. Additionally, examples of M may include metal elements (such as Sc, Y, B, Al, Ga, and In).

[0122] The composition of the halide-based solid electrolyte is not particularly limited, but it can be represented by 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 ≤ 6, and b + c = 6). At this time, a can be 0.75 or greater, 1 or greater, and a can be 1.5 or less. b can be 1 or greater, and can be 2 or greater. Additionally, c can be 3 or greater, and can be 4 or greater. Specific examples of the halide-based solid electrolyte can be Li3YBr6, Li3YCl6, or Li3YBr2Cl4.

[0123] The electrolyte layer may further include a binder. At this time, the binder can be styrene-butadiene rubber, nitrile rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, acrylate polymer, or a combination thereof, but is not limited thereto, and any material used as a binder in the art can be used. The acrylate polymer can be butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0124] The thickness of the solid electrolyte layer can be, for example, 1 μm to 150 μm.

[0125] The electrolyte layer may further include an alkali metal salt, an ionic liquid, or a combination thereof.

[0126] The alkali metal salt may be, for example, a lithium salt. The amount of the lithium salt in the solid electrolyte layer may be greater than or equal to 1 M, for example, 1 M to 4 M. In this case, the lithium salt can increase the ionic conductivity by increasing the lithium ion mobility of the solid electrolyte layer.

[0127] The lithium salt may include, for example, 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 oxalyl difluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide, LiFSI, LiN(SO2F)2, LiCF3SO3, LiAsF6, LiSbF6, LiClO4, or a mixture thereof.

[0128] In addition, the lithium salt may be an imide salt. For example, the imide lithium salt may be lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2) and lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2). The lithium salt can maintain or increase the ionic conductivity by appropriately maintaining the chemical reactivity with the ionic liquid.

[0129] The ionic liquid has a melting point lower than room temperature, so it is in a liquid state at room temperature, and refers to a salt composed only of ions or a room temperature molten salt.

[0130] The ionic liquid may be a compound including: a) at least one cation selected from the group consisting of ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolinium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof; and b) at least one anion selected from the group consisting of 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 - 。

[0131] The ionic liquid can be, for example, one or more selected from 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.

[0132] In the solid electrolyte layer, the solid electrolyte and the ionic liquid can be used in a weight ratio of 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.

[0133] The solid electrolyte layer can be formed by adding the solid electrolyte to a binder solution, coating it on a base film, and drying the resulting product. The solvent of the binder solution can be isobutyl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. The formation process of the solid electrolyte layer is well known in the art, and thus its detailed description will be omitted.

[0134] In an embodiment, the all-solid-state battery can further include a buffer material to buffer the thickness change that occurs during charging and discharging. The buffer material can be present between the negative electrode and the casing, and in the case of a battery in which one or more electrode assemblies are stacked therein, the buffer material can be present between different electrode assemblies.

[0135] The buffer material can include a material having an elastic recovery rate of 50% or more and having an insulating function, and specifically, can include silicone rubber, acrylic rubber, fluororubber, nylon, synthetic rubber, or a combination thereof. The buffer material can be present in the form of a polymer sheet.

[0136] Figure 3 is a cross-sectional view of an all-solid-state battery according to an embodiment. Refer to Figure 3, the all-solid-state battery 100 may have a structure in which the electrode assembly is housed in a housing (such as a pouch), and in this electrode assembly, a negative electrode 400 including a negative electrode current collector 401 and a negative electrode layer 403, a solid electrolyte layer 300, and a positive electrode 200 including a positive electrode active material layer 203 and a positive electrode current collector 201 are stacked. The all-solid-state battery 100 may further include an elastic layer 500 on the outer surface of at least one of the positive electrode 200 and the negative electrode 400. Figure 3 One electrode assembly including a negative electrode 400, a solid electrolyte layer 300, and a positive electrode 200 is illustrated, but an all-solid-state battery can be manufactured by stacking two or more electrode assemblies.

[0137] Figure 4 Schematically illustrates the structure of an all-solid-state battery (for example, an all-solid-state battery in a charged state) according to another embodiment. 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 400', including a negative electrode current collector 401 and a negative electrode layer 403'; and a solid electrolyte 300 between the positive electrode 200 and the negative electrode 400', and including a battery housing 500 that houses these.

[0138] In addition, lithium ions are deintercalated from the positive electrode active material and deposited on the negative electrode current collector 401', and as a result, a lithium deposition layer 405' is located between the current collector (401') and the negative electrode layer 403'.

[0139] Examples

[0140] Hereinafter, examples and comparative examples of the present invention will be described. However, these examples should not be construed as limiting the scope of the present invention in any sense.

[0141] (Example 1)

[0142] (1) Fabrication of the positive electrode

[0143] By mixing a LiNi 0.8 Co 0.1 Al 0.1 O2 positive electrode active material, a Li6PS5Cl argyrodite-type first solid electrolyte with an average particle size (D 50 ) of 5 μm, a carbon nanotube conductive material, and a polyvinylidene fluoride binder in an isobutyl isobutyrate solvent to prepare a first region slurry. At this time, the mixing ratio of the positive electrode active material, the first solid electrolyte, the conductive material, and the binder is set to a weight ratio of 85:13.3:0.4:1.3.

[0144] By mixing a LiNi 0.8 Co 0.1 Al 0.1The O2 positive electrode active material, with an average particle size (D 50 ) of 1 μm, the Li6PS5Cl argyrodite-type second solid electrolyte, and the carbon nanotube conductive material are mixed in a zinc acetate solvent to prepare the second region slurry. At this time, the mixing ratio of the positive electrode active material, the second solid electrolyte, the conductive material, and the binder is set to a weight ratio of 85:13.3:0.4:1.3.

[0145] The second region slurry is coated on an aluminum current collector, then dried and pressed at 60 °C to form the second region, and the first region slurry is coated on this second region, then dried and pressed at 60 °C to form the first region, thereby manufacturing a positive electrode for a all-solid-state battery single cell. Here, the thickness of the second region is 35 μm, and the thickness of the first region is 35 μm.

[0146] (2) Fabrication of the negative electrode

[0147] A negative electrode coating composition is prepared by mixing a polyvinylidene fluoride binder, Ag nanoparticles (D 50 : 60 nm), and carbon black in an N-methylpyrrolidone solvent. The carbon black is a mixture of single particles with a particle size of 38 nm and secondary particles (where primary particles with a particle size of 76 nm are aggregated into secondary particles with a particle size of 275 nm). The binder, Ag nanoparticles, and carbon black are mixed at a weight ratio of 5:23.75:71.25.

[0148] The negative electrode coating composition is coated on a stainless steel current collector, then vacuum dried and pressed at 100 °C to manufacture a negative electrode including a negative electrode coating with a thickness of 7 μm and a current collector with a thickness of 10 μm.

[0149] (3) Fabrication of the solid electrolyte layer

[0150] An isobutyl isobutyrate binder solution (solid content: 50 wt%) prepared by adding butyl acrylate as an acrylate polymer is added to the argyrodite-type solid electrolyte of Li6PS5Cl, and then mixed. Here, the solid electrolyte and the binder are mixed at a weight ratio of 98.7:1.3.

[0151] The mixing process is carried out using a Thinky mixer. Subsequently, 2 mm zirconia balls are added to the obtained mixture, and then stirred again using a Thinky mixer to prepare a slurry. The slurry is cast on a polytetrafluoroethylene release film and then dried at room temperature to manufacture a 60-μm-thick solid electrolyte layer.

[0152] (3) Fabrication of the all-solid-state battery single cell

[0153] The negative electrode, solid-state electrolyte, and positive electrode were stacked in sequence and pressed with a pressure of 2 Nm to fabricate a full-solid-state battery cell. In the fabricated battery cell, the thickness of the positive electrode layer (excluding the current collector) was 70 μm, the thickness of the negative electrode layer (excluding the current collector) was 7 μm, and the thickness of the solid-state electrolyte layer was 60 μm.

[0154] (Example 2)

[0155] The positive electrode was fabricated in the same manner as in Example 1, except that the first-region slurry was prepared using the argyrodite-type first solid-state electrolyte Li6PS5Cl with an average particle size (D 50 ) of 3 μm.

[0156] The positive electrode was used together with the negative electrode and solid-state electrolyte according to Example 1 to fabricate a full-solid-state battery cell.

[0157] (Example 3)

[0158] The positive electrode was fabricated in the same manner as in Example 1, except that the second-region slurry was prepared using the argyrodite-type second solid-state electrolyte Li6PS5Cl with an average particle size (D 50 ) of 3 μm.

[0159] The positive electrode was used together with the negative electrode and solid-state electrolyte according to Example 1 to fabricate a full-solid-state battery cell.

[0160] (Example 4)

[0161] The positive electrode was fabricated in the same manner as in Example 1, except that the first-region slurry was prepared using the argyrodite-type first solid-state electrolyte Li6PS5Cl with an average particle size (D 50 ) of 10 μm.

[0162] The positive electrode was used together with the negative electrode and solid-state electrolyte according to Example 1 to fabricate a full-solid-state battery cell.

[0163] (Comparative Example 1)

[0164] The positive electrode was fabricated in the same manner as in Example 1, except that the first-region slurry was prepared using the argyrodite-type first solid-state electrolyte Li6PS5Cl with an average particle size (D 50 ) of 1 μm, and the second-region slurry was prepared using the argyrodite-type second solid-state electrolyte Li6PS5Cl with an average particle size (D 50 ) of 5 μm.

[0165] The positive electrode was used together with the negative electrode and solid-state electrolyte according to Example 1 to fabricate a full-solid-state battery cell.

[0166] (Comparative Example 2)

[0167] The positive electrode was fabricated in the same manner as in Comparative Example 1, except that the argyrodite-type second solid electrolyte Li6PS5Cl with an average particle size (D 50 ) of 3 μm was used to prepare the second region slurry.

[0168] The positive electrode was used together with the negative electrode and the solid electrolyte according to Example 1 to fabricate an all-solid-state battery cell.

[0169] (Comparative Example 3)

[0170] By mixing LiNi 0.8 Co 0.1 Al 0.1 O2 positive electrode active material, argyrodite-type solid electrolyte Li6PS5Cl with an average particle size (D 50 ) of 1 μm, carbon nanotube conductive material, and polyvinylidene fluoride binder in isobutyl isobutyrate solvent to prepare the positive electrode layer slurry. At this time, the mixing ratio of the positive electrode active material, the solid electrolyte, the conductive material, and the binder was set to a weight ratio of 85:13.3:0.4:1.3.

[0171] The positive electrode slurry was coated on an aluminum current collector, dried at 60 °C, and subjected to a pressing process to fabricate a positive electrode for an all-solid-state battery. At this time, the thickness of the positive electrode layer was 70 μm.

[0172] (Comparative Example 4)

[0173] The all-solid-state battery positive electrode was fabricated in the same manner as in Comparative Example 3, except that the argyrodite-type solid electrolyte Li6PS5Cl with an average particle size (D 50 ) of 5 μm was used to prepare the positive electrode slurry.

[0174] The positive electrode was used together with the negative electrode and the solid electrolyte according to Example 1 to fabricate an all-solid-state battery cell.

[0175] (Example 5)

[0176] By mixing LiNi 0.8 Co 0.1 Al 0.1 O2 positive electrode active material, average particle size (D 50) Prepare the second slurry for the third region by mixing a Li6PS5Cl garnet-type solid electrolyte with a particle size of 2 μm and a carbon nanotube conductive material in a zinc acetate solvent, and prepare the first slurry for the third region using a Li6PS5Cl garnet-type solid electrolyte with an average particle size of 3.5 μm. At this time, the mixing ratio of the positive electrode active material, solid electrolyte, conductive material, and binder in the final positive electrode is 85:13.3:0.4:1.3 by weight.

[0177] Coat the second region slurry prepared in Example 1 on an aluminum current collector, dry it at 60 °C, and perform a pressing process to form the second region. Coat the second slurry of the third region on the second region, dry it at 60 °C, and then coat the first slurry of the third region on it, dry it at 60 °C, and perform a pressing process to form the third region. Next, coat the first region slurry prepared in Example 1, dry it at 60 °C, and perform a pressing process to fabricate a positive electrode for an all-solid-state battery including the formed first region. At this time, the thickness of the second region is 20 μm, the thickness of the third region is 30 μm, and the thickness of the first region is 20 μm. Additionally, the average size of the third solid electrolyte particles in the third region is 2.8 μm.

[0178] The positive electrode configurations according to Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in Table 1.

[0179] (Table 1)

[0180]

[0181] Experimental Example 1) Evaluation of Ionic Conductivity and Electronic Conductivity

[0182] Measure the ionic conductivity and electronic conductivity of the positive electrodes according to Examples 1 to 5 and Comparative Examples 1 to 4. The results are shown in Table 2.

[0183] At room temperature (25 °C), each positive electrode is sampled as 10Φ (diameter of 10 mm), and after applying a torque of 10 N·m, measure the ionic conductivity and electronic conductivity using a resistance spectrometer. Here, at the open-circuit potential, scan the frequency from 500 kHz to 50 mHz with an amplitude of 50 mV.

[0184] The results are shown in Table 2.

[0185] (Table 2)

[0186] Ionic Conductivity (S / cm) Electronic Conductivity (S / cm) Example 1 0.23 1.21 Example 2 0.18 1.15 Example 3 0.34 1.13 Example 4 0.30 1.17 Example 5 0.38 1.18 Comparative Example 1 0.17 1.11 Comparative Example 2 0.11 1.15 Comparative Example 3 0.08 1.13 Comparative Example 4 0.17 1.21

[0187] As shown in Table 2, the electronic conductivities of Examples 1 to 5 are somewhat similar to those of Comparative Examples 1 to 4, but the ionic conductivities in Comparative Examples 1 to 4 are very excellent.

[0188] Although the present disclosure has been described in connection with exemplary embodiments presently regarded as practical, it should be understood that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims.

Claims

1. A all-solid-state battery, comprising: A negative electrode; An electrolyte layer; And A positive electrode, comprising 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 first solid electrolyte particles, The second region includes second solid electrolyte particles, and The average particle size of the first solid electrolyte particles is greater than the average particle size of the second solid electrolyte particles.

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

40.

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

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

5. The all-solid-state battery according to claim 3, wherein the second region corresponds to a thickness greater than or equal to 30% of the total thickness of the positive electrode layer.

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

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

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

40.

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

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

11. The all-solid-state battery according to claim 1, wherein the thickness ratio of the first region to 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. The all-solid-state battery according to claim 12, wherein based on 100% of the total thickness of the positive electrode layer, the first region corresponds to a thickness less than or equal to 56% and greater than or equal to 24%, and based on 100% of the total thickness of the positive electrode layer, the second region corresponds to a thickness greater than or equal to 24% and less than or equal to 56%.

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. The all-solid-state battery according to claim 12, wherein the third region includes third solid electrolyte particles, and the third solid electrolyte particles 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.

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

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

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

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

20. The all-solid-state battery according to claim 12, wherein the third region is divided into two to five zones in the thickness direction, the zone in contact with the first region is the first zone, the zone in contact with the second region is the nth zone, and in the nth zone, the average particle size of the third solid electrolyte particles increases in the direction of the first region.

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