Electrolyte composite for all-solid-state lithium ion secondary battery and all-solid-state lithium ion secondary battery comprising same

Abstract

Disclosed are an electrolyte composite for an all-solid-state lithium ion secondary battery and an all-solid-state lithium ion secondary battery comprising same, the electrolyte composite being capable of enhancing battery performance by applying different solid electrolytes to the cathode side and the anode side of the all-solid-state lithium ion secondary battery, respectively. The electrolyte composite for an all-solid-state lithium ion secondary battery comprises two types of phase-separated solid electrolytes, wherein a first solid electrolyte disposed at the cathode side and a second solid electrolyte disposed at the anode side to form a layered structure.

Description

Electrolyte composite for all-solid-state lithium-ion secondary batteries and all-solid-state lithium-ion secondary batteries containing the same

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0103773, filed August 5, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrolyte composite applicable to an all-solid-state lithium-ion secondary battery and an all-solid-state lithium-ion secondary battery including the same, and more particularly, to an electrolyte composite for an all-solid-state lithium-ion secondary battery, which can improve the performance of the battery by applying different solid electrolytes to each of the positive and negative electrode sides of the all-solid-state lithium-ion secondary battery, and an all-solid-state lithium-ion secondary battery including the same.

[0003] From the perspectives of battery capacity, safety, output, large-scale development, and miniaturization, various batteries are being studied to overcome the limitations of lithium secondary batteries, which are currently widely commercialized. Representative examples include metal-air batteries, which have much larger theoretical capacities than lithium secondary batteries in terms of capacity; all-solid-state batteries, which have no risk of explosion compared to lithium secondary batteries in terms of safety; super capacitors for output; sodium-sulfur batteries (NaS batteries) or redox flow batteries (RFBs) for large-scale development; and thin film batteries for miniaturization. These are all being continuously studied in academia and industry.

[0004] Among these, all-solid-state batteries are batteries that replace the liquid electrolyte used in lithium secondary batteries with a solid one. Accordingly, since flammable solvents are not used, there is no risk of fire or explosion due to decomposition reactions of conventional electrolytes, so safety can be significantly improved. Furthermore, since all-solid-state batteries can use lithium metal or a lithium alloy as the anode active material, they have the advantage of being able to dramatically improve the energy density for the mass and volume of the battery. Furthermore, the capacity density (capacity per unit weight) of lithium is approximately 10 times that of graphite, which is generally used as an anode active material. Therefore, when lithium is used as the anode active material, it is possible to increase the output of all-solid-state batteries while making them thinner.

[0005] As such a conventional all-solid-state battery, a battery is known that includes a metal layer formed of a metal that forms an alloy with lithium as an anode active material layer, and has an interface layer made of amorphous carbon on the anode active material layer. In addition, in this type of all-solid-state battery, when charging, metallic lithium is deposited between the amorphous carbon interface layer and the anode active material layer, and when discharging, the deposited metallic lithium is ionized and moves toward the cathode. However, when the all-solid-state battery as described above is repeatedly charged and discharged, the metallic lithium deposited between the amorphous carbon interface layer and the anode active material layer is ionized and dissolved, which may cause a problem in that a void is created, making it impossible to use the battery.

[0006] To address these issues, the industry has developed an all-solid-state battery comprised of a carbon-containing anode (i.e., a lithium-free anode) excluding a lithium metal layer. The anode of this all-solid-state battery does not contain lithium in the initial state or after complete discharge, and when overcharged, lithium ions moved from the positive electrode form an alloy or compound between the negative electrode current collector and the solid electrolyte, which can function as a negative electrode active material (i.e., lithium metal is plated on the surface of the negative electrode current collector during charging).

[0007] All-solid-state batteries, such as the above, are manufactured by interposing a solid electrolyte membrane between the positive and negative electrodes and then performing high-pressure pressing. To form a composite comprising a positive electrode layer, an electrolyte layer, and a negative electrode layer, processes typically employing a free-standing electrolyte membrane, transferring the electrolyte membrane to the electrode, or overcoating the electrode with the electrolyte membrane are utilized. Overcoating the electrode with the electrolyte membrane offers the advantages of high process efficiency and the ability to realize the electrolyte layer in a thin film form.

[0008] However, overcoating an electrolyte film on an electrode also presents a problem: the electrolyte slurry can permeate the electrode, react with it, and cause irreversible side reactions in the battery. Therefore, a method is needed that suppresses irreversible side reactions and improves battery output characteristics while overcoating an electrolyte film on the electrode.

[0009] Accordingly, the purpose of the present invention is to provide an electrolyte composite for an all-solid-state lithium-ion secondary battery, which can improve the performance of the battery by applying different solid electrolytes to each of the positive and negative electrode sides of the all-solid-state lithium-ion secondary battery, and an all-solid-state lithium-ion secondary battery including the same.

[0010] To achieve the above object, the present invention provides an electrolyte composite for an all-solid-state lithium-ion secondary battery, comprising two types of phase-separated solid electrolytes, a first solid electrolyte disposed on the positive electrode side; and a second solid electrolyte disposed on the negative electrode side, which form a layered structure.

[0011] In addition, the present invention provides an all-solid-state lithium ion secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte composite layer disposed between the positive electrode and the negative electrode and including the electrolyte composite.

[0012] According to the electrolyte composite for an all-solid-state lithium-ion secondary battery according to the present invention, and the all-solid-state lithium-ion secondary battery including the same, different solid electrolytes are applied to each of the positive and negative electrode sides of the all-solid-state lithium-ion secondary battery, thereby suppressing irreversible side reactions of the battery, thereby having the advantage of improving the performance of the battery, such as output characteristics.

[0013] Figure 1 is a schematic diagram showing an electrolyte complex according to one embodiment of the present invention interposed between an anode and a cathode.

[0014] Figure 2 is a cross-sectional schematic diagram showing the configuration of an all-solid-state lithium-ion secondary battery according to one embodiment of the present invention.

[0015] Figure 3 is a cross-sectional schematic diagram showing the configuration of an all-solid-state lithium-ion secondary battery according to one embodiment of the present invention.

[0016] Figure 4 is a graph showing the performance of an all-solid-state lithium-ion secondary battery manufactured according to one embodiment and a comparative example of the present invention.

[0017] Hereinafter, the present invention will be described in detail with reference to the attached drawings.

[0018] FIG. 1 is a schematic diagram showing an electrolyte composite according to one embodiment of the present invention interposed between a positive electrode and a negative electrode. As illustrated in FIG. 1, the electrolyte composite for an all-solid-state lithium-ion secondary battery according to the present invention comprises two types of phase-separated solid electrolytes, and a first solid electrolyte (20) disposed on the positive electrode (10) side and a second solid electrolyte (40) disposed on the negative electrode (30) side form a layered structure.

[0019] The above-described all-solid-state lithium-ion secondary battery electrolyte composite is formed by drying an electrolyte slurry, and when applied to an all-solid-state lithium-ion secondary battery, it is formed by overcoating and drying the electrolyte slurry on an electrode. The all-solid-state lithium-ion secondary battery electrolyte composite of the present invention can suppress irreversible side reactions of a battery or electrode and improve output characteristics by having two types of phase-separated solid electrolyte layers each containing electrolytes of different compositions.

[0020] The above first solid electrolyte (20) is applied to the surface of the positive electrode, and may be applied to at least a portion of the surface of components constituting the positive electrode, such as the positive electrode active material, for example.

[0021] The above first solid electrolyte (20) may be in an amorphous state, a crystalline state, or a mixed state of amorphous and crystalline.

[0022] In addition, the first solid electrolyte (20) may include at least one selected from among a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte, but it is preferable to include only a sulfide-based solid electrolyte.

[0023] More specifically, the first solid electrolyte (20) basically includes a first sulfide-based solid electrolyte and a first binder.

[0024] The above first sulfide-based solid electrolyte has an argyrodite-type crystal structure and includes a compound represented by the following formula 1.

[0025] [Formula 1]

[0026] Li (6-x) PS (5-x) Cl (1+x-y) Br (y)

[0027] In the above equation 1, x is 0 < x < 0.6, and y is 0.4 < y < 1.

[0028] In the compound of the above formula 1 included in the first sulfide-based solid electrolyte, if the x value or y value is outside the above range, the performance of the first solid electrolyte (20) may deteriorate, which may adversely affect the performance of the battery. In particular, if the y value in the compound represented by the above formula 1 is 0.4 or less or 1 or more, the ionic conductivity of the first solid electrolyte (20) may decrease, which may cause a problem of deteriorating the output characteristics of the battery.

[0029] The above first sulfide-based solid electrolyte is, as needed, Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m and n are positive numbers, Z is one of Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q(p and q are positive numbers, M is one of P, Si, Ge, B, Al, Ga or In), or a combination thereof. At this time, when using something including Li2S-P2S5, the mixing molar ratio of Li2S and P2S5 can be selected in the range of, for example, Li2S:P2S5=50:50 to 90:10.

[0030] However, in order for the first solid electrolyte (20) to exhibit optimal performance, it is preferable that the first sulfide-based solid electrolyte contain only the compound represented by the above formula 1.

[0031] The first binder included in the first solid electrolyte (20) plays a central role in or assists in the adhesion between the first solid electrolyte (20) and the second solid electrolyte (40) and the adhesion between the first solid electrolyte (20) and the positive electrode (10).

[0032] The first binder preferably basically includes a rubber-based binder, and may further include at least one selected from the group consisting of acrylonitrile copolymers, acrylonitrile-styrene-butadiene copolymers, polyethylene, polypropylene, chlorosulfonated polyethylene, polyvinylpyrrolidone, cellulose acetate, cellulose acetate butyrate, polyamide, polyimide, polycarboxylate, and compounds exhibiting similar properties to these.

[0033] Examples of the above rubber-based binder include butadiene rubbers such as butadiene rubber (BR), styrene butadiene rubber (SBR), acrylic styrene butadiene rubber (ASBR), acrylonitrile-butadiene rubber (ABR), nitrile butadiene rubber (NBR), and hydrogenated nitrile butadiene rubber (HNBR), acrylic rubbers, and fluorine rubbers, and one or more of these may be included.

[0034] However, it may be more preferable that the first binder basically includes nitrile butadiene rubber.

[0035] The above first binder may be the same as or different from the second binder included in the second solid electrolyte (40) described later. In addition, the above first binder may be the same as or different from the binder included in the positive electrode (10).

[0036] The content ratio of the first sulfide-based solid electrolyte and the first binder included in the first solid electrolyte (20) may be 90:10 to 98:2, preferably 91:9 to 97:3, and more preferably 93:7 to 95:5 in terms of weight ratio.

[0037] If the content of the first binder is less than 2 wt%, problems such as the electrolyte slurry not being dispersed due to insufficient binder content may occur.

[0038] In addition, if the content of the first binder exceeds 10 wt%, problems such as gelation of the electrolyte slurry may occur due to excessive binder content.

[0039] Meanwhile, during the manufacturing of the first solid electrolyte (20), a first solvent may be included in the first electrolyte slurry. The first solvent serves to dissolve the first binder, and includes a solvent having a dielectric constant of more than 0 and less than 20, preferably 0.1 to 10, and more preferably 0.3 to 5. In particular, since a sulfide-based solid electrolyte has a characteristic of its structure collapsing when reacted with a polar organic solvent, the upper limit of the dielectric constant of the first solvent should be less than 20.

[0040] More specifically, the first electrolyte slurry may include at least one of the following solvents having a dielectric constant greater than 0 and less than 20. These solvents include butyrate compounds such as n-butyl butyrate, iso-butyl butyrate, pentyl butyrate, hexyl butyrate, and heptyl butyrate; sulfone compounds such as ethylmethyl sulfone and tetramethylene sulfone; nitrile compounds such as acetonitrile; carbonate compounds such as propylene carbonate; gamma-butyrolactone; toluene compounds; xylene compounds; anisole compounds; Examples thereof include benzene compounds; methane hydrocarbon compounds having 6 or more carbon atoms, such as hexane, heptane, nonane, and decane; methane hydrocarbon compounds containing a halogen element, such as dibromomethane and dichloromethane; chloroform compounds; and acetate compounds, such as benzyl acetate and octyl acetate.

[0041] It may be preferable that the first solvent above includes at least one of a butyrate-based compound, a toluene-based compound, a xylene-based compound, an anisole-based compound, and an acetate-based compound, and it may be more preferable that the first solvent basically includes a butyrate-based compound.

[0042] Next, the second solid electrolyte (40) is applied to the surface of the cathode, and may be applied to at least a portion of the surface of components constituting the cathode, for example, carbon particles or inorganic particles.

[0043] The above second solid electrolyte (40) may be in an amorphous state, like the first solid electrolyte (20), or in a crystalline state, or may be in a mixed state of amorphous and crystalline.

[0044] In addition, the second solid electrolyte (40) may include at least one selected from among a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte, but it is preferable to include only a sulfide-based solid electrolyte, as with the first solid electrolyte (20).

[0045] More specifically, the second solid electrolyte (40) basically includes a second sulfide-based solid electrolyte and a second binder.

[0046] The above second sulfide-based solid electrolyte has an argyrodite-type crystal structure and includes a compound represented by the following formula 2.

[0047] [Formula 2]

[0048] Li (6-x) PS (5-x) Cl (1+x-y) Br (y)

[0049] In the above equation 2, x is 0 < x < 0.6, and y is 0 ≤ y < 0.4.

[0050] In the compound of the above formula 2 included in the second sulfide-based solid electrolyte, if the x or y value is outside the above range, the performance of the second solid electrolyte (40) may deteriorate, which may adversely affect the performance of the battery. In particular, if the y value is 0.4 or more in the compound represented by the above formula 2, a problem may occur in which the electrolyte is eluted into the solvent, causing a side reaction with the electrode during the overcoating process.

[0051] The second sulfide-based solid electrolyte is, as needed, Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m and n are positive numbers, Z is one of Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, M is one of P, Si, Ge, B, Al, Ga or In), or a combination thereof. At this time, when using something including Li2S-P2S5, the mixing molar ratio of Li2S and P2S5 can be selected in the range of, for example, Li2S:P2S5=50:50 to 90:10.

[0052] However, in order for the second solid electrolyte (40) to exhibit optimal performance, it is preferable that the second sulfide-based solid electrolyte contain only the compound represented by the above formula 2.

[0053] The second binder included in the second solid electrolyte (40) plays a central role in or assists in the adhesion between the first solid electrolyte (20) and the second solid electrolyte (40) and the adhesion between the second solid electrolyte (40) and the negative electrode (30).

[0054] The second binder, like the first binder, preferably also basically includes a rubber-based binder, and may further include at least one selected from the group consisting of acrylonitrile copolymers, acrylonitrile-styrene-butadiene copolymers, polyethylene, polypropylene, chlorosulfonated polyethylene, polyvinylpyrrolidone, cellulose acetate, cellulose acetate butyrate, polyamide, polyimide, polycarboxylate, and compounds exhibiting similar properties to these.

[0055] Examples of the above rubber-based binder include butadiene rubbers such as butadiene rubber (BR), styrene butadiene rubber (SBR), acrylic styrene butadiene rubber (ASBR), acrylonitrile-butadiene rubber (ABR), nitrile butadiene rubber (NBR), and hydrogenated nitrile butadiene rubber (HNBR), acrylic rubbers, and fluorine rubbers, and one or more of these may be included.

[0056] However, it may be more preferable that the second binder basically includes nitrile butadiene rubber.

[0057] The second binder as described above may be the same as or different from the first binder included in the first solid electrolyte (20) as described above. In addition, the second binder may be the same as or different from the binder included in the negative electrode (30).

[0058] The content ratio of the second sulfide-based solid electrolyte and the second binder included in the second solid electrolyte (40) may be 90:10 to 98:2, preferably 91:9 to 97:3, and more preferably 93:7 to 95:5 in terms of weight ratio.

[0059] If the content of the second binder is less than 2 wt%, problems such as the electrolyte slurry not being dispersed due to insufficient binder content may occur.

[0060] In addition, if the content of the second binder exceeds 10 wt%, problems such as gelation of the electrolyte slurry may occur due to excessive binder content.

[0061] Meanwhile, during the manufacture of the second solid electrolyte (40), a second solvent may be included in the second electrolyte slurry. The second solvent serves to dissolve the second binder, and includes a solvent having a dielectric constant of more than 0 and less than 20, preferably 0.1 to 10, and more preferably 0.3 to 5. In particular, since the sulfide-based solid electrolyte has a characteristic of its structure collapsing when reacted with a polar organic solvent, the upper limit of the dielectric constant of the second solvent should also be less than 20, similar to the first solvent.

[0062] More specifically, the second electrolyte slurry may include at least one of the following solvents having a dielectric constant greater than 0 and less than 20. These solvents include butyrate compounds such as n-butyl butyrate, iso-butyl butyrate, pentyl butyrate, hexyl butyrate, and heptyl butyrate; sulfone compounds such as ethylmethyl sulfone and tetramethylene sulfone; nitrile compounds such as acetonitrile; carbonate compounds such as propylene carbonate; gamma-butyrolactone; toluene compounds; xylene compounds; anisole compounds; Examples thereof include benzene compounds; methane hydrocarbon compounds having 6 or more carbon atoms, such as hexane, heptane, nonane, and decane; methane hydrocarbon compounds containing a halogen element, such as dibromomethane and dichloromethane; chloroform compounds; and acetate compounds, such as benzyl acetate and octyl acetate.

[0063] It may be preferable that the second solvent includes at least one of a butyrate-based compound, a toluene-based compound, a xylene-based compound, an anisole-based compound, and an acetate-based compound, and it may be more preferable that the second solvent basically includes a butyrate-based compound.

[0064] Meanwhile, the thickness ratio of the first solid electrolyte (20) and the second solid electrolyte (40) may be 50 to 80:50 to 20, preferably 60 to 70:40 to 30, and more preferably about 65:35.

[0065] If the thickness of the second solid electrolyte (40) exceeds 50% of the total thickness of the first solid electrolyte (20) and the second solid electrolyte (40), the ionic conductivity of the entire solid electrolyte membrane may decrease, resulting in a deterioration in the output characteristics.

[0066] In addition, when the thickness of the second solid electrolyte (40) is less than 20% of the total thickness of the first solid electrolyte (20) and the second solid electrolyte (40), a problem of increasing unevenness in the thickness of the second solid electrolyte (40) layer may occur during slurry coating.

[0067] In addition, each of the first solid electrolyte (20) and the second solid electrolyte (40) may further include one or more of a crosslinking monomer and an inorganic particle, if necessary.

[0068] The above crosslinking monomer is capable of forming a polymer matrix by crosslinking the positive electrode and the electrolyte through a photopolymerization or thermal polymerization reaction, and may be exemplified by at least one selected from among trimethylolpropane ethoxylate triacrylate, polyethyleneglycol diacrylate, triethyleneglycol diacrylate, trimethylopropaneethoxylate triacrylate, bisphenol A ethoxylate dimethacrylate, derivatives thereof, and mixtures thereof.

[0069] The above inorganic particles can be evenly dispersed in the electrolyte complex and used to improve the mechanical strength of the solid electrolyte, and include alumina (Al2O3), silicon dioxide (SiO2), titanium dioxide (TiO2), barium titanate (BaTiO3), lithium oxide (Li2O), lithium fluoride (LiF), lithium hydroxide (LiOH), lithium nitride (Li3N), barium oxide (BaO), sodium oxide (Na2O), lithium carbonate (Li2CO3), calcium carbonate (CaCO3), lithium aluminate (LiAlO2), strontium titanate (SrTiO3), tin oxide (SnO2), selenium oxide (CeO2), magnesium oxide (MgO), nickel oxide (NiO), calcium oxide (CaO), zinc oxide (ZnO), zirconium dioxide (ZrO2), silicon carbide (SiC), and derivatives thereof. and one or more selected from mixtures thereof.

[0070] Continuing, an all-solid-state lithium-ion secondary battery including the electrolyte composite for an all-solid-state lithium-ion secondary battery described above is described.

[0071] The above-mentioned all-solid-state lithium-ion secondary battery includes the electrolyte complex and an electrode facing the electrolyte complex, and is preferably a sulfide-based all-solid-state lithium-ion secondary battery.

[0072] FIG. 2 is a cross-sectional schematic diagram showing the configuration of an all-solid-state lithium-ion secondary battery according to one embodiment of the present invention. The all-solid-state lithium-ion secondary battery (1000) according to one embodiment of the present invention is a so-called lithium-ion secondary battery that performs charging and discharging by lithium ions moving between a positive electrode (100) and a negative electrode (200). Specifically, as illustrated in FIG. 2, the all-solid-state lithium-ion secondary battery (1000) includes a positive electrode (100), a negative electrode (200), and an electrolyte composite layer (300) disposed between the positive electrode (100) and the negative electrode (200) and including the electrolyte composite. Hereinafter, each of these will be described.

[0073] anode

[0074] As illustrated in FIG. 2, the positive electrode (100) includes a positive electrode active material layer (140) and a positive electrode current collector (120) sequentially arranged in the direction of the negative electrode (200). The positive electrode current collector (120) may have a plate shape or a foil shape. The positive electrode current collector (120) may be, for example, one type of metal selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium, or an alloy of two or more types of metals.

[0075] The positive electrode active material layer (140) can reversibly absorb and release lithium ions. In addition, the positive electrode active material layer (140) includes a positive electrode active material and may further include a solid electrolyte. The positive electrode active material may be a compound capable of insertion / de-insertion of lithium. Examples of the compound capable of insertion / de-insertion of lithium include Li a A 1-b B' b D'2(0.90≤a≤1.8, 0≤b≤0.5); Li a E1- b B' b O 2-c D' c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b B' b O 4-c D' c (0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b B' c D' α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Co b B' c O 2-α F' α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Lia Ni 1-b-c Mn b B' c D' α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤ 0.1); Li a Ni b Co c Mn d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤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'O2; LiNiVO4; Li (3-f) J2(PO4)3(0≤f≤2); Li (3-f) It can be expressed as one of Fe2(PO4)3(0≤f≤2); LiFePO4.

[0076] In the above chemical formula, A is Ni, Co, Mn or a combination thereof, B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof, D' is O, F, S, P or a combination thereof, E is Co, Mn or a combination thereof, F' is F, S, P or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof, Q is Ti, Mo, Mn or a combination thereof, I' is Cr, V, Fe, Sc, Y or a combination thereof, and J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0077] Specific examples of the positive electrode active material include lithium salts such as lithium cobaltate (LCO), lithium nickelate, lithium nickel cobaltate, lithium nickel cobalt aluminumate (NCA), lithium nickel cobalt manganese (NCM), lithium manganese acid, and lithium iron phosphate, and lithium sulfide. The positive electrode active material layer (140) may include only one selected from these compounds as the positive electrode active material, or may include two or more.

[0078] The above-described positive electrode active material may include a lithium salt of a transition metal oxide having a layered rock salt structure among the lithium salts described above. Here, the layered rock salt structure refers to a structure in which oxygen atomic layers and metal atomic layers are alternately and regularly arranged in the direction of the cubic rock salt structure, and as a result, each atomic layer forms a two-dimensional plane. In addition, the cubic rock salt structure refers to a sodium chloride structure, which is a type of crystal structure. For example, the cubic rock salt structure refers to a structure in which face-centered cubic lattices in which cations and anions are respectively formed are arranged with a displacement of half of the edges of the unit cell.

[0079] Lithium salts of transition metal oxides having this layered rock salt structure include, for example, LiNi x Co y Al zO2(NCA) or LiNi x Co y Mn z It may be a ternary lithium transition metal oxide such as O2(NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1). The positive electrode active material layer (140) may include a lithium salt of a ternary transition metal oxide having such a layered rock salt structure as a positive electrode active material, thereby improving the energy density and thermal stability of an all-solid-state lithium ion secondary battery (1000).

[0080] Examples of the shape of the positive electrode active material include spherical, elliptical, and other particle shapes. In addition, the particle size of the positive electrode active material is not particularly limited and may be within a range applicable to positive electrode active materials of a typical all-solid-state lithium-ion secondary battery. In addition, the content of the positive electrode active material in the positive electrode active material layer (140) is also not particularly limited and may be within a range applicable to positive electrodes of a typical all-solid-state lithium-ion secondary battery.

[0081] In addition, the compound having a coating layer on the surface can be used, and the compound and the compound having the coating layer can be mixed and used. The coating layer can include a coating element compound of an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compounds forming these coating layers can be amorphous or crystalline. Examples of the coating elements included in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof, and a specific example of the coating layer includes Li2O-ZrO2, etc. The coating layer forming process can use any coating method as long as it can coat the compound with these elements in a method that does not adversely affect the properties of the positive electrode active material (for example, spray coating, dipping, etc.), and since this is well understood by those working in this field, a detailed description thereof will be omitted.

[0082] The solid electrolyte that may be further included in the positive electrode active material layer (140) may be the same as or different from the solid electrolyte included in the electrolyte composite layer (300) described below. In addition, the positive electrode active material layer (140) may be a mixture of not only the positive electrode active material and the solid electrolyte described above, but also additives such as a conductive agent, a binder, a filler, a dispersant, or an ion conductive assistant. Examples of the conductive agent include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or metal powder. In addition, the binder is mixed with the active material and the conductive agent to bind each component and assist in particle growth, and examples thereof include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. In addition, the filler, dispersant, or ion conductive auxiliary agent may be exemplified by known materials commonly used in electrodes of all-solid-state lithium-ion secondary batteries. In addition, the positive electrode active material layer (140) may include the positive electrode active material, conductive agent, and binder in granular form.

[0083] cathode

[0084] Next, the negative electrode (200) includes a negative electrode active material layer (240) positioned closer to the positive electrode (100) side and in contact with the electrolyte composite layer (300), and a negative electrode current collector (220) positioned at the outermost portion or the like based on the stacking direction, facing the opposite side of the negative electrode active material layer (240) that does not contact the electrolyte composite layer (300). In addition, the negative electrode may not include a separate lithium metal except for the lithium metal formed during charging (i.e., corresponding to a non-anode all-solid-state battery).

[0085] Negative active material layer

[0086] The above-described negative electrode active material layer (240) may include one or more types of negative electrode active materials capable of forming an alloy or compound with lithium. In the initial state or after complete discharge, lithium may not be included between the negative electrode current collector (220), the negative electrode active material layer (240), or the negative electrode active material layer (240) and the electrolyte composite layer (300). Fig. 3 is a cross-sectional schematic diagram showing the configuration of an all-solid-state lithium ion secondary battery according to one embodiment of the present invention.

[0087] As described below, when the all-solid-state lithium ion secondary battery (1000) according to one embodiment is overcharged, the negative active material included in the negative active material layer (240) and the lithium ions that have moved from the positive electrode (100) form an alloy or compound, so that, for example, as illustrated in FIG. 3, a metal layer (260) containing lithium as a main component may be formed (deposited) on the negative electrode (200). The metal layer (260) may be formed by being deposited between the negative current collector (220) and the negative active material layer (240), inside the negative active material layer (240), or both. When the metal layer (260) is positioned between the negative electrode current collector (220) and the negative electrode active material layer (240), the metal layer (260) may be formed closer to the negative electrode current collector layer (220) than to the negative electrode active material layer (240).

[0088] The negative electrode active material layer (240) according to one embodiment of the present invention may include at least one lithium-friendly material selected from the group consisting of silver (Ag), gold (Au), platinum (Pt), zinc (Zn), silicon (Si), magnesium (Mg), copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), manganese monoxide (MnO), silicon dioxide (SiO2), titanium dioxide (TiO2), alumina (Al2O3), zinc peroxide (ZnO2), and lithium fluoride (LiF) as the negative electrode active material. In addition, it may be more preferable to apply silver (Ag) as the lithium-friendly material among these. However, the present invention is not limited thereto, and any lithium-friendly material having similar physical properties or characteristics to these may be applied without any special limitation.

[0089] Accordingly, the metal layer (260) formed during overcharge may include a Li (lithium affinity material) alloy including a γ1 phase, a βLi phase, or a combination thereof in which the lithium affinity material is dissolved in lithium. Therefore, during discharge, only Li is dissolved in the Li (lithium affinity material) alloy constituting the metal layer (260), and the dissolved lithium affinity material remains, thereby suppressing the occurrence of pores. In this case, the content of the lithium affinity material in the precipitated Li-lithium affinity material solid solution may be 60 wt% or less. Within this range, the decrease in the average discharge potential due to the influence of the lithium affinity material can be effectively suppressed. On the other hand, if the content of the lithium affinity material in the precipitated Li-lithium affinity material solid solution is too low, the amount of lithium affinity material remaining during discharge becomes small, and it may be difficult to sufficiently suppress the occurrence of pores. For this reason, the content of the lithium-affinity material in the precipitated Li-lithium-affinity material solid solution may be 20 wt% or more, for example, 40 wt% or more.

[0090] In one embodiment of the present invention, the lithium-affinity material does not necessarily need to be uniformly present in the negative electrode active material layer (240), and may be distributed in the negative electrode current collector (220) side of the negative electrode active material layer (240). In this case, lithium ions may react with the lithium-affinity material distribution layer in the negative electrode active material layer (240) that has reached the vicinity of the negative electrode current collector (220), thereby forming a Li (lithium-affinity material) alloy as a metal layer (260).

[0091] If the content of the lithium-affinity material included in the negative electrode active material layer (240) is excessively low, it may be difficult to suppress the occurrence of pores because the lithium-affinity material remaining during discharge also decreases. Therefore, the negative electrode active material layer (240) may include 10 wt% or more, preferably 20 wt% or more, of the lithium-affinity material based on 100 wt% of the total negative electrode active material included in the negative electrode active material layer (240) in the initial state before charge / discharge is performed. Meanwhile, in the relationship between the reaction potential of the lithium-affinity material and Li, if the lithium-affinity material increases, the average discharge potential may decrease, which may lower the energy density of the battery. Therefore, from the viewpoint of high energy density, the upper limit of the content of the lithium-affinity material may be preferably 50 wt% or less based on 100 wt% of the total negative electrode active material included in the negative electrode active material layer (240).

[0092] In addition, in the negative electrode active material layer (240), if the content of the lithium-affinity material per unit area is excessively low when viewed in the stacking direction of the negative electrode (200), it may be difficult to suppress the occurrence of pores because the lithium-affinity material remaining during discharge also decreases. Therefore, the content of the lithium-affinity material per unit area in the negative electrode active material layer (240) is 0.05 mg / cm 2 Ideally, 0.10 mg / cm 2On the other hand, if the content of lithium-affinity material per unit area is too high, the average discharge potential may decrease, which may lower the energy density of the battery. Therefore, the upper limit of the content of lithium-affinity material per unit area is 5 mg / cm. 2 Below, preferably 2 mg / cm 2 It could be as follows:

[0093] In addition, in the initial state before charge / discharge, the lithium-affinity material included in the negative electrode active material layer (240) may be in the form of particles or a film. When the lithium-affinity material exists in the form of particles, the average particle diameter (d50, diameter length or average diameter) of the lithium-affinity material may be, but is not limited to, 20 nm to 1 μm.

[0094] Meanwhile, the negative electrode active material layer (240) may include a carbon material as a negative electrode active material in addition to a lithium-friendly material. Amorphous carbon may be preferably used as the carbon material included in the negative electrode active material layer (240). Specific examples of the amorphous carbon include amorphous carbon black (amorphous acetylene black, amorphous furnace black, amorphous Ketjen black), amorphous activated carbon, amorphous graphene, and combinations thereof. However, among the negative electrode active material layers (240), by positioning a carbon material having a relatively small particle size on the interface side that comes into contact with the electrolyte composite layer (300), the interface of the negative electrode active material layer (240) that comes into contact with the electrolyte composite layer (300) can be made flatter. Based on 100 wt% of the total negative active material included in the negative active material layer (240), the negative active material other than the lithium-compatible material may be combined to be 50 wt% or more, for example, 70 wt% or more. The content of the negative active material other than the lithium-compatible material may be measured using the same method as the method for measuring the content of the lithium-compatible material.

[0095] And, the carbon material included in the negative electrode active material layer (240) may contain oxygen. More specifically, the carbon material particles constituting the carbon material may contain 2 to 10 at% of oxygen. When the oxygen is included in the range of 2 to 10 at%, the surface roughness of the negative electrode active material layer and the operating characteristics of the battery may be further improved. In one embodiment of the present invention, the oxygen may exist in a form included in a functional group bonded to the carbon material particles. In addition, the functional group may include at least one selected from the group consisting of a carboxyl group, a hydroxyl group, an ether group, an ester group, an aldehyde group, a carbonyl group, and an amide group.

[0096] The carbon material particles containing 2 to 10 at% of oxygen can be produced, for example, by a method of oxidizing the carbon material. For example, the carbon material can be treated with an acid, stirred and reacted at a temperature of 25 to 60°C, to introduce oxygen functional groups to the surface of the carbon material. The type of the acid is not particularly limited, and any acid that can introduce oxygen functional groups to the surface of the carbon material can be used. Examples of the acid include sulfuric acid, nitric acid, or mixtures thereof, and an oxidizing agent such as potassium permanganate can also be used.

[0097] The content of oxygen contained in the above carbon material particles can be measured using a photoelectron spectroscopy (XPS or ESCA). For example, it can be measured using a K-Alpha (Thermo Fisher Scientific) device. In one embodiment of the present invention, the oxygen may be present on the surface of the carbon material particles. The surface does not mean only the outer surface of the carbon material particles, but also includes, for example, the inner surface of the pores if pores exist.

[0098] And, when the carbon material contains oxygen as described above, the negative electrode active material layer (240) may contain 2 to 10 at% of oxygen, 65 to 85 at% of carbon, and 0.5 to 5 at% of silver, and preferably may contain 2.5 to 5 at% of oxygen, 74 to 85 at% of carbon, and 0.5 to 3 at% of silver. In addition, the negative electrode active material layer (240) may further contain 5 to 25 at% of fluorine (F), and preferably 10 to 20 at% of fluorine (F). In addition, the negative electrode active material layer (240) may further contain 0.01 to 1 at% of sulfur (S), and preferably 0.01 to 0.5 at% of sulfur (S). In one embodiment of the present invention, the negative active material layer (240) may include 2 to 10 at% of oxygen, 65 to 85 at% of carbon, 0.5 to 5 at% of silver, and 5 to 25 at% of fluorine, preferably 2.5 to 5 at% of oxygen, 74 to 85 at% of carbon, 0.5 to 3 at% of silver, and 10 to 20 at% of fluorine, and may further include sulfur. The above atomic composition ratios may be measured using a photoelectron spectroscopy (XPS or ESCA). For example, the composition ratios may be measured using a Nexsa4 (Thermo Fisher Scientific) device.

[0099] Meanwhile, the negative electrode active material layer (240) may further include a binder for the purpose of stabilizing the negative electrode active material layer (240) on the negative electrode current collector (220). The binder may be, for example, a resin such as styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. In addition, the negative electrode active material layer (240) may appropriately contain additives used in conventional all-solid-state batteries, such as fillers, dispersants, and ion conductive additives. Specific examples of the additives are the same as those described in the positive electrode section described above.

[0100] The total thickness of the negative electrode active material layer (240) is not particularly limited and may be, for example, 1 to 100 μm. If the thickness of the negative electrode active material layer (240) is less than 1 μm, the performance of the all-solid-state battery may not be sufficient. In addition, if the thickness of the negative electrode active material layer (240) exceeds 100 μm, the resistance of the negative electrode active material layer (240) increases, resulting in insufficient performance of the all-solid-state battery. For reference, by using the binder mentioned above, the thickness of the negative electrode active material layer (240) can be easily secured at an appropriate level.

[0101] negative current collector

[0102] The negative electrode current collector (220) may be positioned at the outermost side in the stacking direction, facing the opposite side of the negative electrode active material layer (240) that does not contact the electrolyte composite layer (300), as illustrated in FIG. 2. However, if the battery includes a structure of more than a bi-cell, it may be positioned at a location other than the outermost side in the stacking direction.

[0103] The negative electrode current collector (220) may be plate-shaped or foil-shaped. The negative electrode current collector (220) may include a material that does not react with lithium, i.e., does not form any alloy or compound with lithium. Examples of materials constituting the negative electrode current collector (220) include copper, aluminum, stainless steel, titanium, iron, cobalt, and nickel. In addition, the negative electrode current collector (220) may be composed of one type of these metals, or may be composed of an alloy of two or more types of metals or a clad material.

[0104] Initial charge capacity ratio

[0105] Meanwhile, in an all-solid-state lithium ion secondary battery (1000) according to one embodiment, the initial charge capacity of the positive electrode active material layer (140) may be configured to be excessively large compared to the initial charge capacity of the negative electrode active material layer (240). As described below, the all-solid-state lithium ion secondary battery (1000) according to one embodiment can be used by charging (i.e., overcharging) exceeding the initial charge capacity of the negative electrode active material layer (240). In the initial stage of charging, lithium may be absorbed into the negative electrode active material layer (240). That is, the negative electrode active material may form an alloy or compound with lithium ions that have moved from the positive electrode (100). When charging is performed exceeding the initial charge capacity of the negative electrode active material layer (240), as illustrated in FIG. 3, lithium may be precipitated on the back surface of the negative electrode active material layer (240), i.e., between the negative electrode current collector (220) and the negative electrode active material layer (240), and a metal layer (260) may be formed by this lithium. The metal layer (260) may be mainly composed of lithium in which a lithium-affinity material is dissolved (i.e., lithium-affinity material-Li solid solution). This phenomenon may be caused by a material that forms an alloy or compound with the lithium-affinity material included in the negative electrode, for example. During discharge, lithium in the negative electrode active material layer (240) and the metal layer (260) may be ionized and move toward the positive electrode (100) while leaving the dissolved lithium-affinity material. Therefore, lithium may be used as the negative electrode active material in an all-solid-state lithium ion secondary battery (1000). In addition, since the lithium-affinity layer (230) and the negative electrode active material layer (240) coat the metal layer (260) at the same time, they function as a protective layer for the metal layer (260) and can suppress the precipitation and growth of dendritic metallic lithium. In this way, short-circuiting and capacity reduction of the all-solid-state lithium ion secondary battery (1000) can be suppressed, and further, the characteristics of the all-solid-state lithium ion secondary battery (1000) can be improved. In addition, according to one embodiment, since the metal layer (260) is not formed in advance, there is also an advantage of being able to reduce the manufacturing cost of the all-solid-state lithium ion secondary battery (1000).

[0106] In an all-solid-state lithium-ion secondary battery (1000) according to one embodiment, it is preferable that the ratio (b+c / a) of the initial charge capacity of the positive electrode active material layer (140) to the initial charge capacity of the negative electrode active material layer (240) and the lithium affinity layer (230) satisfies the following equation.

[0107] [Formula 3]

[0108] 0.01< b+c / a < 0.5

[0109] In the above equation 3, a is the initial charge capacity (mAh) of the positive active material layer (140), b is the initial charge capacity (mAh) of the negative active material layer (240), and c is the initial charge capacity (mAh) of the lithium affinity layer (230).

[0110] At this time, if the initial charge capacity ratio is 0.01 or less, the lithium affinity layer (230) and the negative electrode active material layer (240) may not function sufficiently as a protective layer, which may deteriorate the characteristics of the all-solid-state lithium ion secondary battery (1000). For example, if the thickness of the lithium affinity layer (230) and the negative electrode active material layer (240) is very thin, the capacity ratio may become 0.01 or less. In this case, there is a concern that the lithium affinity layer (230) and the negative electrode active material layer (240) may collapse due to repeated charge and discharge, and dendritic metallic lithium may precipitate and grow. As a result, the characteristics of the all-solid-state lithium ion secondary battery (1000) may deteriorate. On the other hand, if the initial charge capacity ratio is 0.5 or more, the battery capacity may decrease because the amount of lithium precipitated from the negative electrode decreases.

[0111] Manufacturing method of all-solid-state lithium-ion secondary battery

[0112] Next, a method for manufacturing the all-solid-state lithium ion secondary battery (1000) will be described. The all-solid-state lithium ion secondary battery (1000) according to one embodiment may be manufactured by manufacturing a positive electrode (100), a negative electrode (200), and an electrolyte composite layer (300) separately and then laminating them. In addition, the all-solid-state lithium ion secondary battery (1000) according to another embodiment may be manufactured by forming a first solid electrolyte on one surface of the positive electrode (100), separately forming a second solid electrolyte on one surface of the negative electrode (200), and then laminating the first solid electrolyte and the second solid electrolyte so that they face each other.

[0113] The above-described positive electrode manufacturing process first adds materials (positive electrode active material, binder, etc.) constituting the positive electrode active material layer (140) to a non-polar solvent to prepare a slurry (or paste), and then applies the prepared slurry onto a positive electrode current collector (120) and dries it to obtain a laminate. Then, the laminate can be pressed, for example, with hydrostatic pressure, etc., to manufacture a positive electrode (100). At this time, the pressing process can be omitted.

[0114] Next, the negative electrode manufacturing process adds materials constituting the negative electrode active material layer (240) (negative electrode active material including carbon material and lithium-friendly material, binder, etc.) to a polar solvent or a non-polar solvent to manufacture a slurry (or paste), and then applies the manufactured slurry onto a negative electrode current collector (220) surface-treated with a lithium-friendly material and then dries to obtain a laminate (however, it may be composed of only the negative electrode current collector surface-treated with a lithium-friendly material without the negative electrode active material layer). At this time, the process of surface-treating the negative electrode current collector with the lithium-friendly material may be by a method selected from the group consisting of an atomic layer deposition method, a sputtering method, and a plasma method. Subsequently, the laminate may be pressurized, for example, by hydrostatic pressure, to manufacture the negative electrode (200). At this time, the pressurizing process may be omitted. In addition, the method of applying the slurry to the negative electrode collector (220) is not particularly limited, and for example, screen printing, metal mask printing, electrostatic painting, dip coating, spray coating, roll coating, doctor blade, gravure coating, etc. can be used.

[0115] In a state where an electrolyte complex layer (300) is interposed between the positive electrode (100) and negative electrode (200) manufactured in this manner, an all-solid-state lithium ion secondary battery (1000) according to one embodiment can be manufactured by applying pressure, for example, using hydrostatic pressure.

[0116] The all-solid-state lithium ion secondary battery (1000) of the present invention can be manufactured in the form of a unit cell having a structure of a cathode / electrolyte composite layer / negative electrode, a bi-cell having a structure of a cathode / electrolyte composite layer / negative electrode / electrolyte composite layer / positive electrode, or a laminated battery having a structure of a unit cell that repeats. In addition, the all-solid-state lithium ion secondary battery according to the present invention can be utilized as a semi-solid battery by including a liquid electrolyte if necessary, and in this case, a separate polymer separator can be further included.

[0117] The shape of the all-solid-state lithium ion secondary battery (1000) of the present invention is not particularly limited, and examples thereof include coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, and cone-shaped batteries. Furthermore, the all-solid-state lithium ion secondary battery (1000) can be applied to large-scale batteries used in electric vehicles, etc. For example, the all-solid-state lithium ion secondary battery (1000) can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). Furthermore, it can be used in fields requiring large amounts of power storage, such as electric bicycles or power tools.

[0118] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0119] [Example 1] Manufacture of an all-solid-state lithium-ion secondary battery

[0120] Manufacturing of cathode / electrolyte composites

[0121] First, 80 g of lithium transition metal oxide, 6.5 g of carbon black, 9.83 g of nitrile butadiene rubber (binder), and 8.17 g of butyl butyrate (solvent) were placed in a Thinky mixer container and mixed 12 times at 2,000 rpm for 3 minutes each to prepare a cathode slurry. Next, using a spray coating method, the prepared cathode slurry was applied to the surface of a cathode current collector (aluminum foil), vacuum-dried at 100°C for 10 hours, and then pressurized with hydrostatic pressure to prepare a cathode.

[0122] Continuing, a sulfide-based solid electrolyte (Li) is added so that the solid content becomes 45 to 60 wt%. 5.7 PS 4.7 Cl 0.4 Br 0.9) 10g, butadiene rubber (binder) 0.3g, and butyl butyrate (solvent) 10.3g were mixed, placed in a Thinky mixer container, and mixed 12 times for 3 minutes each at 2,000 rpm to prepare a first electrolyte slurry. Then, using a bar coater, the first electrolyte slurry was applied to the surface of the active material of the prepared positive electrode, and then vacuum-dried at 70°C for 5 hours to prepare a positive electrode / electrolyte composite.

[0123] Manufacturing of cathode / electrolyte composites

[0124] First, 6.5 g of carbon black, 9.83 g of PVdF binder (solid content 6%), and 8.17 g of NMP solution were placed in a Thinky mixer container and mixed 12 times at 2,000 rpm for 3 minutes each to prepare a negative active material slurry. Next, using a spray coating method, the prepared negative active material slurry was applied to the surface of a negative electrode current collector (SUS foil), vacuum dried at 100°C for 10 hours, and then pressurized with hydrostatic pressure to prepare a negative electrode.

[0125] Continuing, a sulfide-based solid electrolyte (Li) is added so that the solid content becomes 45 to 60 wt%. 5.6 PS 4.6 Cl 1.4 ) 10g, butadiene rubber (binder) 0.3g, and butyl butyrate (solvent) 10.3g were mixed, placed in a Thinky mixer container, and mixed 12 times for 3 minutes each at 2,000 rpm to prepare a second electrolyte slurry. Then, the second electrolyte slurry was applied to the surface of the active material of the manufactured negative electrode using a bar coater, and then vacuum-dried at 70°C for 5 hours to prepare a negative electrode / electrolyte composite.

[0126] All-solid-state battery manufacturing

[0127] The above-mentioned positive electrode / electrolyte complex and negative electrode / electrolyte complex were laminated so that the electrolytes faced each other, and then covered with a pouch made of polypropylene, sealed, and isostatically pressed for 30 minutes to manufacture an all-solid-state battery laminated in the order of negative electrode / second solid electrolyte / first solid electrolyte / positive electrode.

[0128] [Comparative Example 1] Manufacturing of an All-Solid-State Lithium-Ion Secondary Battery

[0129] The electrolyte (i.e., the first electrolyte) applied to the positive electrode / electrolyte composite of Example 1 was coated on the surface of the active material of the negative electrode manufactured in Example 1 (coating conditions, etc. were the same as in Example 1), and then the positive electrode manufactured in Example 1 was laminated on the surface of the electrolyte so that the active material of the positive electrode and the electrolyte faced each other. Then, the laminate was covered with a pouch made of polypropylene, sealed, and isostatically pressed for 30 minutes to manufacture an all-solid-state battery laminated in the order of negative electrode / first solid electrolyte / positive electrode.

[0130] [Comparative Example 2] Manufacturing of an All-Solid-State Lithium-Ion Secondary Battery

[0131] The positive electrode manufactured in Example 1 was laminated on the surface of the electrolyte (i.e., the second electrolyte) of the negative electrode / electrolyte composite manufactured in Example 1, such that the active material of the positive electrode and the electrolyte of the negative electrode / electrolyte composite faced each other. Subsequently, the laminate was covered with a pouch made of polypropylene, sealed, and isostatically pressed for 30 minutes, thereby manufacturing an all-solid-state battery laminated in the order of negative electrode / second solid electrolyte / positive electrode.

[0132] [Comparative Example 3] Manufacturing of an All-Solid-State Lithium-Ion Secondary Battery

[0133] An all-solid-state battery was manufactured by stacking negative electrode / first solid electrolyte / second solid electrolyte / positive electrode in the same manner as in Example 1, except that the electrolytes in the positive electrode / electrolyte composite and the negative electrode / electrolyte composite manufactured in Example 1 were swapped.

[0134] [Experimental Example 1] Performance Evaluation of All-Solid-State Battery

[0135] For each of the all-solid-state batteries manufactured in Example 1 and Comparative Examples 1 to 3, a driving pressure of 10 MPa was applied using a jig, and charging and discharging were performed under the following conditions while a constant driving pressure was applied to evaluate the capacity retention rate according to the charge and discharge cycle, and the results are shown in Table 1 and Figure 4 below.

[0136] - Charge / discharge conditions: Charge to 4.25 V in CC / CV mode at an operating temperature of 60°C and 0.33 C, discharge to 3.0 V with a constant current, and repeat charge / discharge 50 times.

[0137] 0.1C initial capacity (mAh g) -1 )0.1C Initial efficiency (%)1C Expression capacity (mAh g -1 ) Example 1185.986.0175.8 Comparative Example 1181.584.5170.0 Comparative Example 2185.386.1163.8 Comparative Example 3183.185.1168.8

[0138] As described above, as a result of evaluating the performance of the all-solid-state batteries manufactured in Example 1 and Comparative Examples 1 to 3, it was confirmed that the battery of Example 1, in which electrolytes having different compositions were coated on the positive and negative electrode sides, did not exhibit the conventional problem of the electrolyte being eluted into a solvent and causing a side reaction between the electrode and the electrolyte even though the electrolyte was overcoated on the electrode, and thus the output characteristics such as the initial capacity efficiency of the battery were improved.

[0139] On the other hand, a first solid electrolyte (Li) is placed between the positive and negative electrodes. 5.7 PS 4.7 Cl 0.4 Br 0.9 ) The battery of Comparative Example 1, which only included one type of electrolyte containing an excessive amount of Br, showed a phenomenon of initial efficiency decline due to the electrolyte being eluted into the solvent during the overcoating process and a side reaction occurring between the electrode and the electrolyte.

[0140] Additionally, a second solid electrolyte (Li) is placed between the positive and negative electrodes.5.6 PS 4.6 Cl 1.4 ) was included, it was confirmed that the output characteristics of the battery were reduced due to the fact that it contained only one type of electrolyte with relatively low ionic conductivity, that is, one type of electrolyte that did not contain Br.

[0141] In addition, the battery of Comparative Example 3, in which the electrolytes were swapped between the positive electrode / electrolyte composite and the negative electrode / electrolyte composite manufactured in Example 1, exhibited phenomena such as a decrease in initial efficiency due to electrolyte dissolution and side reactions occurring during the process of overcoating the first solid electrolyte on the negative electrode.

[0142] Through the above results, it can be seen that the conventional problems are not improved when only one type (first solid electrolyte or second solid electrolyte) of the electrolyte complex provided by the present invention is used, or when the same electrolyte complex is used, unless the specific position of the electrolyte complex disclosed by the present invention is followed.

[0143] [Explanation of symbols]

[0144] 10, 100: positive

[0145] 20: First solid electrolyte

[0146] 30, 200: cathode

[0147] 40: Second solid electrolyte

[0148] 120: Positive current collector

[0149] 140: Positive electrode active material layer

[0150] 220: Negative current collector

[0151] 240: Negative active material layer

[0152] 260: Metal layer

[0153] 300: Electrolyte complex layer

[0154] 1000: All-solid-state lithium-ion secondary battery

Claims

1. 2 Contains phase-separated solid electrolytes, An electrolyte composite for an all-solid-state lithium-ion secondary battery, comprising: a first solid electrolyte disposed on the positive electrode side; and a second solid electrolyte disposed on the negative electrode side; the electrolyte composite having a layered structure.

2. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that in claim 1, the first solid electrolyte comprises a first sulfide-based solid electrolyte and a first binder, and the first sulfide-based solid electrolyte comprises a compound represented by the following formula 1: [Formula 1] Li (6-x) PS (5-x) Cl (1+x-y) Br (y) In the above equation 1, x is 0 < x < 0.6, and y is 0.4 < y < 1.

3. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the first binder in claim 2 comprises a rubber-based binder.

4. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the rubber-based binder in claim 3 is selected from the group consisting of butadiene-based rubber, acrylic-based rubber, fluorine-based rubber, and combinations thereof.

5. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the content ratio of the first sulfide-based solid electrolyte and the first binder in claim 2 is 90:10 to 98:2 in weight ratio.

6. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that in claim 1, the second solid electrolyte comprises a second sulfide-based solid electrolyte and a second binder, and the second sulfide-based solid electrolyte comprises a compound represented by the following formula 2: [Formula 2] Li (6-x) PS (5-x) Cl (1+x-y) Br (y) In the above equation 2, x is 0 < x < 0.6, and y is 0 ≤ y < 0.

4.

7. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the second binder in claim 6 comprises a rubber-based binder.

8. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the rubber-based binder in claim 7 is selected from the group consisting of butadiene-based rubber, acrylic-based rubber, fluorine-based rubber, and combinations thereof.

9. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the content ratio of the second sulfide-based solid electrolyte and the second binder in claim 6 is 90:10 to 98:2 in weight ratio.

10. An electrolyte composite for an all-solid-state lithium-ion secondary battery, characterized in that the thickness ratio of the first solid electrolyte and the second solid electrolyte in claim 1 is 50 to 80:50 to 20.

11. An all-solid-state lithium ion secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte composite layer disposed between the positive electrode and the negative electrode and including the electrolyte composite of claim 1.

12. An all-solid-state lithium-ion secondary battery according to claim 11, characterized in that the negative electrode does not contain a separate lithium metal other than lithium metal formed when the battery is charged.

13. An all-solid-state lithium-ion secondary battery according to claim 11, characterized in that the all-solid-state lithium-ion secondary battery is a sulfide-based all-solid-state lithium-ion secondary battery.

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