Positive active material for sulfide-based all-solid-state battery

Abstract

The present invention relates to a positive electrode active material for all-solid-state batteries, wherein the positive electrode active material has the following structure: a shell containing metal sulfide particles of a specific size is adsorbed on the surface of a core containing lithium metal oxide, thereby reducing the cracks that may occur between the positive electrode active material and the solid electrolyte and their reactivity, thus having the advantages of improving lithium ion mobility and achieving high charge and discharge capacity.

Description

Technical Field

[0001] This invention relates to a positive electrode active material for sulfide-based all-solid-state batteries.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0127344, dated September 27, 2021, and the entire contents of that Korean Patent Application are incorporated herein by reference as a part thereof. Background Technology

[0003] Lithium-ion all-solid-state batteries are batteries that directly convert chemical energy into electrical energy by using sulfide-based or oxide-based solid electrolytes and oxidizing or reducing lithium ions through all-solid-state materials. In particular, sustainable rechargeable batteries can solve the problems of low energy density, high cost, and toxicity that currently limit commercial lithium-ion rechargeable batteries due to advantages such as eco-friendliness, safety, and high energy density storage capacity. Therefore, the demand for sustainable rechargeable batteries is constantly increasing.

[0004] However, all-solid-state batteries have several drawbacks, such as irreversibility due to interfacial side reactions between sulfide or oxide solid electrolytes and the positive electrode during charge and discharge; and reduced battery capacity due to uneven electrode charge distribution caused by interfacial resistance and the formation of a space charge layer. Furthermore, the low ionic conductivity of the all-solid-state materials themselves hinders the commercialization of lithium-ion all-solid-state batteries as a next-generation battery technology.

[0005] To address these issues, positive electrode active materials using lithium metal sulfides and other dielectrics have been developed. However, the positive electrode active materials developed to date suffer from the following problems: although they offer significantly improved charge-discharge performance and capacity compared to oxide-based positive electrode active materials, their capacity retention during charge and discharge is significantly lower than that of current oxide-based positive or negative electrode active materials.

[0006] Furthermore, although a technology has been developed in which surface-treating positive electrode active materials such as metal oxides are used in all-solid-state batteries, its effect on improving charge and discharge performance is negligible, or although it does improve charge and discharge performance, it is limited by the high cost of the raw materials used, making it unsuitable for commercialization.

[0007] [Related Technical Documents]

[0008] [Patent Literature]

[0009] Korean Patent Registration No. 10-1582394 Summary of the Invention

[0010] [Technical Issues]

[0011] Therefore, the object of the present invention is to provide a positive electrode active material for sulfide-based all-solid-state batteries, wherein the lithium-ion mobility is improved by preventing cracks that may occur between the positive electrode active material and the solid electrolyte or by preventing side reactions that may occur between them.

[0012] [Technical Solution]

[0013] To solve the above problems,

[0014] In one embodiment, the present invention provides a positive electrode active material for all-solid-state batteries, comprising:

[0015] A core comprising a lithium metal oxide as shown in Formula 1 below; and

[0016] Adsorbed on the surface of the core, containing metal sulfides (M 2 S) The shell of the particle,

[0017] The average particle size of the metal sulfide particles ranges from 0.1 nm to 40 nm.

[0018] [Chemical Formula 1]

[0019] Li x [Ni y Co z Mn w M 1 v ]O u

[0020] in,

[0021] M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0022] x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01, and 0.01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5。

[0023] In this case, metal sulfides (M 2 S) particles may include single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al or Ti.

[0024] For example, metal sulfides (M 2 S) particles can be zinc sulfide (ZnS) particles.

[0025] Furthermore, based on the total weight of the positive electrode active material, the content of metal sulfide particles can be from 0.1% to 2% by weight.

[0026] In addition, the average particle size of the positive electrode active material can be from 0.5 μm to 10 μm.

[0027] Furthermore, the shell containing metal sulfide particles can be adsorbed onto more than 60% of the total area of ​​the core.

[0028] Furthermore, in one embodiment, the present invention provides a method for manufacturing a positive electrode active material for all-solid-state batteries, comprising:

[0029] Preparation of lithium metal oxides and metal sulfides (M) as shown in Formula 1 2 S) A mixture of particles; and

[0030] The mixture is subjected to heat treatment;

[0031] The average particle size of the metal sulfide particles ranges from 0.1 nm to 40 nm.

[0032] [Chemical Formula 1]

[0033] Li x [Ni y Co z Mn w M 1 v ]O u

[0034] in,

[0035] M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0036] x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01, and 0.01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5。

[0037] In this case, during the preparation of the mixture, the mixture may contain 0.1 to 2% by weight of metal sulfides based on the total weight of the lithium metal oxides.

[0038] Furthermore, the heat treatment can be carried out at 300°C to 500°C, and can be carried out in the presence of one or more inert gases, namely nitrogen and argon.

[0039] Furthermore, in one embodiment, the present invention provides an all-solid-state lithium secondary battery, comprising:

[0040] A positive electrode comprising the above-described positive electrode active material of the present invention;

[0041] Negative electrode; and

[0042] A sulfide-based solid electrolyte placed between the positive and negative electrodes.

[0043] The sulfide-based solid electrolyte may include one or more selected from the group consisting of: Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5.

[0044] [Beneficial Effects]

[0045] The positive electrode active material for all-solid-state batteries of the present invention has the following structure: a shell containing metal sulfide particles of a specific size is adsorbed on the surface of a core containing lithium metal oxide. Therefore, it has the advantage of reducing the cracks or reactivity that may occur between the positive electrode active material and the solid electrolyte, thereby improving the lithium ion mobility and achieving high charge and discharge capacity. Detailed Implementation

[0046] Because the present invention can have various variations and various implementations, specific implementations will be described in detail in the description.

[0047] However, it is not intended to limit the invention to a particular embodiment, and it should be understood that it includes all modifications, equivalents and substitutions contained within the spirit and scope of the invention.

[0048] In this invention, it should be understood that the terms "comprising" or "having" are intended to specifically describe the presence of the said features, numbers, steps, operations, components, ingredients or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, components or combinations thereof.

[0049] Furthermore, in this invention, when a portion of a layer, film, region, plate, etc., is described as being "on" another portion, this includes not only the case where the portion is "directly" on the other portion, but also the case where there is another portion between them. Conversely, when a portion of a layer, film, region, plate, etc., is described as being "below" another portion, this includes both the case where the portion is "directly" below the other portion and the case where there is another portion between them. Moreover, in this document, "on" includes not only being on top but also being on the bottom.

[0050] Furthermore, in this invention, "comprising as a major component" means that the total weight of the composition (e.g., slurry or a specific component) is 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 97.5% by weight or more, and in some cases, when constituting the entire composition or a specific component, it may mean 100% by weight.

[0051] The invention will be described in more detail below.

[0052] Positive electrode active materials for all-solid-state batteries

[0053] In one embodiment, the present invention provides a positive electrode active material for all-solid-state batteries, comprising:

[0054] Cores containing lithium metal oxide; and

[0055] Adsorbed on the core surface are metal sulfides (M 2 S) The shell of the particle,

[0056] The average particle size of the metal sulfide particles ranges from 0.1 nm to 40 nm.

[0057] The positive electrode active material of the present invention is used in sulfide-based all-solid-state lithium secondary batteries, which contains lithium metal oxide as a core that exhibits electroactive properties during battery charging and discharging, and has metal sulfide (M 2 S) Particles adsorb onto the core surface to form a shell structure.

[0058] Here, lithium metal oxides can be used without particular restrictions, as long as they are lithium metal oxides that provide lithium ions through a reversible reaction during battery charging and discharging. However, specifically, they can include lithium metal oxides represented by the following chemical formula 1.

[0059] [Chemical Formula 1]

[0060] Li x [Ni y Co z Mn w M 1v ]O u

[0061] in,

[0062] M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0063] x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01, and 0.01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5。

[0064] The lithium metal oxide shown in Formula 1 can be an oxide containing lithium and a transition metal, and the transition metal can contain a high content of nickel. For example, the lithium metal oxide can include one or more selected from the group consisting of LiNi. 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.7 Co 0.15 Mn 0.15 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 and LiNi 0.8 Co 0.1 Mn 0.05 Al 0.05 O2. Lithium metal oxides, due to their high nickel content, have an excellent effect on improving battery charge and discharge capacity.

[0065] In addition, the core has metal sulfides (M) adsorbed on its surface. 2 The structure of the shell of the S-particles reduces the interfacial resistance between the positive electrode active material and the solid electrolyte, and improves the battery's electrical performance by enhancing its ability to prevent side reactions between the positive electrode active material and the solid electrolyte and suppressing lithium ion loss.

[0066] In this case, metal sulfides (M2 S) particles are sulfide particles containing transition metals, and specifically, they can be single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al or Ti.

[0067] For example, metal sulfides (M 2 S) Particles can be particles containing zinc sulfide (ZnS) as the main component. Particles containing zinc sulfide as the main component have high state stability compared with other metal sulfides. Therefore, their advantages are that they can not only effectively suppress side reactions between the positive electrode active material and the sulfide solid electrolyte during battery charging and discharging, but also have good processability and are economical.

[0068] Furthermore, based on the total weight of the positive electrode active material, the content of metal sulfide particles can be 0.1 to 2% by weight; specifically, based on the total weight of the positive electrode active material, it can be 0.1 to 2% by weight; 0.1 to 1.5% by weight; 0.3 to 1.5% by weight; 0.5 to 1.5% by weight; 0.9 to 1.5% by weight; 0.3 to 0.9% by weight; or 0.1 to 1.2% by weight.

[0069] According to the present invention, by controlling the content of metal sulfide particles contained in the positive electrode active material within the above-mentioned range, the low content of metal sulfide particles can prevent the surface of lithium metal oxide from being fully surrounded or excessive metal sulfides from agglomerating and not being coated on the surface of lithium metal oxide.

[0070] Furthermore, the average particle size of the positive electrode active material can be from 0.5 μm to 10 μm, and in this case, the average particle size of the metal sulfide particles on the surface of the positive electrode active material can be from 0.1 nm to 40 nm.

[0071] More specifically, the average particle size of the positive electrode active material is 0.5 μm to 8 μm; 0.5 μm to 6 μm; 0.5 μm to 5 μm; 0.5 μm to 4 μm; 5 μm to 9 μm; 1 μm to 4 μm; 2 μm to 4 μm; 4 μm to 7 μm; 0.5 μm to 3 μm; 1 μm to 3 μm; or 3 μm to 8 μm, and the average particle size of the metal sulfide particles on the surface of the positive electrode active material can be 0.1 nm to 30 nm; 0.1 nm to 20 nm; 0.1 nm to 10 nm; 5 nm to 30 nm; 5 nm to 20 nm; 8 nm to 15 nm; or 4 nm to 15 nm.

[0072] By controlling the average particle size of the positive electrode active material within the aforementioned range, the present invention can further improve the electrode activity of the positive electrode. Furthermore, by controlling the average particle size of the metal sulfide particles surrounding the core within the aforementioned range, side reactions at the interface with the solid electrolyte can be effectively suppressed, and cracks that may appear on the surface of the positive electrode active material can be prevented. At the same time, the degradation of the electroactivity of the lithium metal oxide in the core can be minimized.

[0073] Furthermore, the shell containing metal sulfide particles can surround more than 60% of the entire surface of the core containing lithium metal oxide. Specifically, the metal sulfide particles can have a structure in which they are physically and uniformly adsorbed onto, rather than chemically bonded to, the surface of the core containing lithium metal oxide. Here, the area of ​​metal sulfide adsorption is more than 60% of the core surface area, more specifically, more than 70%, more than 80%, more than 90%, more than 95%, or more than 98%. By controlling the area of ​​the shell containing metal sulfide particles adsorbed on the core surface to the above proportion, the present invention can effectively suppress side reactions between the positive electrode active material and the solid electrolyte without using excessive amounts of metal sulfide.

[0074] The positive electrode active material for all-solid-state batteries of the present invention has the following structure: a shell containing metal sulfide particles of a specific size is adsorbed on the surface of a core containing lithium metal oxide. Therefore, it has the advantage of reducing the cracks that may occur between the positive electrode active material and the solid electrolyte and the reactivity between them, thereby improving the lithium ion mobility and enabling high charge and discharge capacity.

[0075] Method for preparing positive electrode active materials for all-solid-state batteries

[0076] Furthermore, in one embodiment, the present invention provides a method for preparing a positive electrode active material for all-solid-state batteries, comprising:

[0077] Preparation of lithium metal oxides and metal sulfides (M) as shown in Formula 1 2 S) A mixture of particles; and

[0078] The mixture is subjected to heat treatment;

[0079] The average particle size of the metal sulfide particles ranges from 0.1 nm to 40 nm.

[0080] [Chemical Formula 1]

[0081] Li x [Ni y Co z Mn w M 1 v ]O u

[0082] in,

[0083] M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0084] x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01, and 0.01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5。

[0085] The method for preparing the positive electrode active material for all-solid-state batteries according to the present invention can be carried out by the following steps: preparing a lithium metal oxide of chemical formula 1 constituting the core and a metal sulfide (M) constituting the shell. 2 A mixture of S) particles, and the mixture is heat-treated.

[0086] In the same conventional method for preparing positive electrode active metal materials, which uses an electrically active lithium metal oxide as a core and forms a shell containing the metal oxide on the core surface, a metal sulfide (M...) will be used to provide... 2 S) "metal (M) 2 A metal chloride and sulfur (S) used to provide the metal sulfide are mixed with lithium metal oxide, thereby forming a metal sulfide (M) on the surface (core) of the lithium metal oxide. 2 It is difficult to uniformly form metal sulfides (M) on a core containing lithium metal oxides, even though the shell is composed of S. 2 S) particles. However, the method of preparing the positive electrode active material of the present invention can be achieved by directly and uniformly mixing lithium metal oxide contained in the core and metal sulfide (M) contained in the shell. 2 S) particles are then subjected to heat treatment to readily prepare core-shell positive electrode active materials.

[0087] In this case, the following equipment can be used to prepare a mixture by mixing lithium metal oxide and metal sulfide particles: dry mixers for mixing powders (e.g., metal compounds) in the art; agitators; oscillators, such as orbital oscillators; slurry mixers; mills, such as planetary ball mills, etc., but not limited thereto.

[0088] As an example, the preparation of the mixture can be carried out using a planetary ball mill at a speed of 50 to 500 rpm per 1 kg of mixture and a force of 1 to 100 kWh / 1 kg for 0.1 to 10 hours.

[0089] As another example, the preparation of the mixture can be carried out by mixing with a shaker for 1 to 10 hours (specifically, 2 to 8 hours).

[0090] Furthermore, in the mixture, the lithium metal oxide represented by Formula 1 can be an oxide comprising lithium and a transition metal, and the transition metal can contain a high content of nickel. For example, the lithium metal oxide can include one or more of the following groups: LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.7 Co 0.15 Mn 0.15 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 and LiNi 0.8 Co 0.1 Mn 0.05 Al 0.05 O2.

[0091] In addition, metal sulfides (M 2 S) particles are sulfide particles containing transition metals, and specifically, they can be single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al or Ti.

[0092] In addition, metal sulfides (M 2 The average particle size of S can be 0.1 nm to 30 nm; 0.1 nm to 20 nm; 0.1 nm to 10 nm; 5 nm to 30 nm; 5 nm to 20 nm; 8 nm to 15 nm; or 4 nm to 15 nm.

[0093] Furthermore, based on the total weight of lithium metal oxides, the content of metal sulfides in the mixture can be 0.1 to 2 wt%, specifically, based on the total weight of lithium metal oxides, 0.1 to 2 wt%; 0.1 to 1.5 wt%; 0.3 to 1.5 wt%; 0.5 to 1.5 wt%; 0.9 to 1.5 wt%; 0.3 to 0.9 wt%; or 0.1 to 1.2 wt%.

[0094] According to the present invention, by controlling the content of metal sulfides mixed with lithium metal oxide within the above-mentioned range, the low content of metal sulfides can prevent the surface of lithium metal oxide from being fully surrounded or excessive metal sulfides from agglomerating and not being coated on the surface of lithium metal oxide.

[0095] Furthermore, the step of heat-treating the mixture containing lithium metal oxide and metal sulfide can be a step of fixing the metal sulfide that is physically adsorbed on the surface of the lithium metal oxide, which serves as the core.

[0096] In this case, the heat treatment step of the mixture can be carried out under inert gas conditions, either alone or in combination, such as nitrogen or argon.

[0097] In addition, the heat treatment temperature can be above 300°C, preferably 300°C to 480°C; 350°C to 500°C; 400°C to 500°C; or 420°C or 480°C.

[0098] According to the present invention, by adjusting the heat treatment temperature of the mixture comprising lithium metal oxide and metal sulfide to the above-mentioned range, the metal sulfide can be easily fixed on the surface of the lithium metal oxide as the core without side reactions.

[0099] The method of manufacturing positive electrode active material for all-solid-state batteries of the present invention can form a shell on the surface of a core containing lithium metal oxide with metal sulfide uniformly coated on it, so that the positive electrode active material with core-shell structure has the following advantages: excellent production efficiency, easy control of the size of metal sulfide to the nanoscale, and excellent processability.

[0100] All-solid-state lithium secondary battery

[0101] Furthermore, in one embodiment, the present invention provides an all-solid-state lithium secondary battery, comprising:

[0102] A positive electrode comprising the positive electrode active material of the present invention described above;

[0103] Negative electrode; and

[0104] A sulfide-based solid electrolyte placed between the positive and negative electrodes.

[0105] Because the all-solid-state lithium secondary battery of the present invention contains a positive electrode containing the positive electrode active material of the present invention described above, the cracks generated at the interface between the positive electrode active material and the solid electrolyte are significantly reduced, the side reactions are suppressed, and the lithium ions in the electrode can have excellent mobility.

[0106] In this case, the positive electrode may have the following structure: a positive electrode mixture layer containing the positive electrode active material of the present invention is formed on the positive electrode current collector.

[0107] There are no particular restrictions on the positive electrode current collector, as long as it has high conductivity and does not cause a chemical reaction in the battery, and it can include, for example: stainless steel; aluminum; nickel; titanium; calcined carbon; or aluminum or stainless steel that has been surface-treated with carbon, nickel, titanium, silver, etc.

[0108] In addition, the positive electrode mixture layer contains positive electrode active material, conductive material, binder and solid electrolyte, and in some cases the positive electrode mixture layer may also contain additives.

[0109] Here, the structure of the positive electrode active material may include: a core comprising a lithium metal oxide as shown in Formula 1; and a metal sulfide (M...) adsorbed on the surface of the core. 2 S) The shell of the particle.

[0110] [Chemical Formula 1]

[0111] Li x [Ni y Co z Mn w M 1 v ]O u

[0112] in,

[0113] M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

[0114] x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01, and 0.01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5。

[0115] There are no particular limitations on lithium metal oxides, as long as they are compounds represented by chemical formula 1. However, specifically, they may include one or more compounds selected from the group consisting of LiNi. 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.7 Co 0.15 Mn 0.15 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 and LiNi 0.8 Co 0.1 Mn 0.05 Al 0.05 O2.

[0116] In addition, this metal sulfide (M 2 S) particles are sulfide particles containing transition metals, and specifically, they can be single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al or Ti.

[0117] In addition, this metal sulfide (M 2 The average particle size of S can be: 0.1 nm to 40 nm; 0.1 nm to 30 nm; 0.1 nm to 20 nm; 0.1 nm to 10 nm; 5 nm to 30 nm; 5 nm to 20 nm; 8 nm to 15 nm; or 4 nm to 15 nm.

[0118] Furthermore, the average particle size of the positive electrode active material can be: 0.5 μm to 10 μm; 0.5 μm to 8 μm; 0.5 μm to 6 μm; 0.5 μm to 5 μm; 0.5 μm to 4 μm; 5 μm to 9 μm; 1 μm to 4 μm; 2 μm to 4 μm; 4 μm to 7 μm; 0.5 μm to 3 μm; 1 μm to 3 μm; or 0.5 μm to 2 μm.

[0119] Furthermore, there are no particular restrictions on the conductive material, as long as it is conductive and does not cause a chemical reaction in the battery. However, specifically, graphite, carbon-based materials, metal powders or metal fibers, needle-like or branched conductive whiskers, conductive metal oxides, conductive polymers, and any one or mixtures thereof can be used. More specifically, graphite, such as natural graphite and artificial graphite; carbon-based materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; needle-like or branched conductive whiskers, such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, and alumina whiskers; conductive metal oxides, such as titanium oxides; or conductive polymers, such as polyphenylene derivatives, and any one or mixtures thereof.

[0120] In addition, the binder for the positive electrode can be any one or a mixture of two or more selected from the following group: N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP); it can also be any one or a mixture of two or more selected from the following group: N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), acrylonitrile-based styrene butadiene rubber (SBR), conjugated diene rubber latex (such as nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), butadiene rubber (BR)), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber and its various copolymers.

[0121] In addition, the negative electrode can have a structure in which a negative electrode mixture layer containing a negative electrode active material is formed on a negative electrode current collector.

[0122] The negative electrode current collector is not particularly limited as long as it has high electrical conductivity and does not cause a chemical reaction in the battery. For example, it can include: stainless steel; copper; nickel; titanium; calcined carbon; or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0123] In addition, the negative electrode mixture layer contains a negative electrode active material, a conductive material, a binder, and a solid electrolyte, and may also contain additives in some cases.

[0124] In this case, the negative electrode active material can be one selected from the following group: lithium metal, lithium alloy, lithium metal composite oxide, lithium-containing titanium composite oxide (LTO), and combinations thereof. Here, the lithium alloy can be an alloy composed of lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn. In addition, the lithium metal composite oxide contains an oxide (MeO x ) of lithium and any metal (Me) selected from Si, Sn, Zn, Mg, Cd, Ce, Ni, and Fe, and can be, for example, Li x Fe2O3 (0 < x ≤ 1) or Li x WO2 (0 < x ≤ 1).

[0125] In addition, as the negative electrode active material, a metal composite oxide can be used, such as Sn x Me 1-x Me' y Oz (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2 and 3 of the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); Oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5 can be used, and carbon-based negative electrode active materials such as crystalline carbon, amorphous carbon or carbon composites can be used alone or in combination of two or more.

[0126] In addition, as the conductive material, examples can be nickel powder, cobalt oxide, titanium oxide, carbon, etc. As carbon, any one selected from Ketjen black, acetylene black, furnace black, graphite, carbon fiber and fullerene can be mentioned, or one or more of them.

[0127] In addition, the binder for the negative electrode can be any one selected from the following group or a mixture of two or more: N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP); it can also be any one selected from the following group or a mixture of two or more: N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), acrylonitrile-based styrene-butadiene rubber (SBR), conjugated diene rubber latex (such as nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), butadiene rubber (BR)), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene / diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber and various copolymers thereof.

[0128] In addition, the solid electrolyte contains sulfide-based particles, and the sulfide-based particles can be electrolytes commonly used in sulfide-based all-solid-state batteries in the art. Specifically, one or more amorphous solid electrolytes selected from the following group can be used: Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5 and Li2S-P2S5.

[0129] The average particle size of the sulfide particles can be from 0.1 μm to 50 μm, specifically, from 0.1 μm to 10 μm. According to the present invention, by controlling the average particle size of the sulfide particles constituting the solid electrolyte within the above-mentioned range, the porosity of the solid electrolyte is increased, thereby improving the problem of battery capacity reduction.

[0130] Example

[0131] The present invention will be described in detail below through examples and experimental cases.

[0132] However, the following embodiments and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the embodiments and experimental examples below.

[0133] Examples 1 to 5 and Comparative Examples 1 to 6: Preparation of positive electrode active materials for sulfide-based all-solid-state batteries

[0134] As shown in Table 1 below, the average particle size of LiNi is 5 ± 0.1 μm relative to 100 parts by weight. 0.8 Co 0.1 Mn 0.1 O2, metal sulfides (M 2 S) is introduced into a ball mill jar and ball-milled for 1 hour at a force of 10 kWh / 1 kg and a speed of 200 ± 50 rpm to obtain LiNi. 0.8 Co 0.1 Mn 0.1 O2 and metal sulfides (M 2 S) A uniformly mixed mixture.

[0135] After transferring the mixture into an oven, it was heat-treated at 450±10℃ for 2 hours to obtain the positive electrode active material (average particle size: 5±0.1μm), in which metal sulfides (M 2 S) Uniformly coated on the LiNi core 0.8 Co 0.1 Mn 0.1 O2 on.

[0136] At this point, as shown in Table 1 below, based on the total weight of lithium metal oxides, when the content of metal sulfides is less than 0.1% by weight, the LiNi core can be determined. 0.8 Co 0.1 Mn 0.1 The surface of O2 cannot be adequately coated; when the content of metal sulfides exceeds 2% by weight, it can be determined that the metal sulfide particles in the mixture aggregate with each other and are not uniformly adsorbed on LiNi. 0.8 Co 0.1 Mn 0.1 The surface of O2.

[0137] Table 1

[0138]

[0139] Examples 6 to 10 and Comparative Examples 7 to 12: Fabrication of sulfide-based all-solid-state batteries

[0140] Sulfide-based all-solid-state batteries were manufactured using each of the positive electrode active materials prepared in Examples 1 to 5 and Comparative Examples 1 to 6 described above.

[0141] Specifically, the positive electrode active material, sulfide solid electrolyte (Li2S-P2S5), conductive material (carbon black), and binder (PVDF) prepared in each embodiment and comparative example were mixed in a weight ratio of 80:15:3:2, coated on an aluminum sheet (thickness: 40 μm), and rolled at room temperature to prepare the positive electrode.

[0142] Lithium metal (Li) thin plates (thickness: 40 μm) were prepared separately as negative electrodes.

[0143] A solid electrolyte membrane (70 μm, 2.8 × 10⁻⁶ m²) was used. -3 S / cm, Li 10 SnP2S 12 It is placed between the prepared positive and negative electrodes to manufacture a sulfide-based all-solid-state battery.

[0144] Table 2

[0145] Positive electrode active material used Example 6 Positive electrode active material of Example 1 Example 7 Positive electrode active material in Example 2 Example 8 Positive electrode active material in Example 3 Example 9 Positive electrode active material of Example 4 Example 10 Positive electrode active material of Example 5 Comparative Example 7 Positive electrode active material of Comparative Example 1 Comparative Example 8 Positive electrode active material of Comparative Example 2 Comparative Example 9 Positive electrode active material of Comparative Example 3 Comparative Example 10 Positive electrode active material of Comparative Example 4 Comparative Example 11 Positive electrode active material of Comparative Example 5 Comparative Example 12 Positive electrode active material of Comparative Example 6

[0146] Experimental Example

[0147] To evaluate the performance of the sulfide-based positive electrode active material of the present invention for all-solid-state batteries, the following experiments were conducted.

[0148] A) Cross-sectional structural analysis of the cathode mixture layer

[0149] Each of the sulfide-based all-solid-state batteries manufactured in Examples 6 to 10 and Comparative Examples 7 to 12 was prepared in a non-standby state and its lifetime was tested at room temperature (25 ± 1 °C) under conditions of 3.0 to 4.25 V and 0.1 C. Each battery was then disassembled and the positive electrode mixture layer was analyzed by scanning electron microscopy (SEM).

[0150] The results confirmed that in the battery of this embodiment of the invention, ZnS (metal sulfide) is uniformly adsorbed on the lithium metal oxide (LiNi) core. 0.8 Co 0.1 Mn 0.1 On the surface of O2). This means that the appearance of cracks at the interface between the lithium metal oxide and sulfide solid electrolyte contained in the core is reduced, and side reactions are suppressed.

[0151] On the other hand, in the comparative example battery, it was determined that the lithium metal oxide (LiNi) used as the core... 0.8 Co 0.1 Mn 0.1 Cracks appeared between O2 and sulfide solid electrolytes.

[0152] Based on these results, the positive electrode active material of the sulfide-based all-solid-state battery of the present invention has the following structure: a shell containing metal sulfide particles of a specific size in a specific amount is adsorbed on the surface of a core containing lithium metal oxide, thereby preventing cracks and side reactions between the lithium metal oxide in the core and the solid electrolyte.

[0153] B) Initial charge and discharge performance evaluation

[0154] Each sulfide-based all-solid-state battery manufactured in Examples 6 to 10 and Comparative Examples 7 to 12 was fixed on a fixture in a chamber at 60°C, and initial charge-discharge was performed at 0.1C to measure the initial charge-discharge capacity and efficiency. Charging was performed in constant current charging (CCC) mode, with the c / o controlled at 0.5C. The results are shown in Table 3 below.

[0155] Table 3

[0156] Initial charging capacity [mAh / g] Initial discharge capacity [mAh / g] Initial charge / discharge efficiency [%) Example 6 211 188 89 Example 7 215 186 87 Example 8 214 182 85 Example 9 222 178 80 Example 10 218 176 81 Comparative Example 7 204 145 71 Comparative Example 8 220 167 76 Comparative Example 9 212 155 73 Comparative Example 10 221 152 69 Comparative Example 11 219 168 77 Comparative Example 12 213 166 78

[0157] As shown in Table 3, because the positive electrode active material of the present invention for all-solid-state batteries has a structure in which a shell containing metal sulfide particles of a specific size is adsorbed on the surface of a core containing lithium metal oxide, the lithium ion mobility is improved and the charge / discharge capacity is also high.

[0158] Based on these results, the positive electrode active material of the present invention for sulfide-based all-solid-state batteries reduces cracks and side reactions at the interface between the positive electrode active material and the solid electrolyte, and has excellent lithium-ion mobility, thus demonstrating the ability to achieve high charge and discharge capacity.

[0159] Although the foregoing has been described according to preferred embodiments of the present invention, it should be understood by those skilled in the art or those of ordinary skill in the art that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.

[0160] Therefore, the scope of the present invention should not be limited to the contents described in the detailed description of this specification, but should be defined by the claims.

Claims

1. A positive electrode active material for all-solid-state batteries, said positive electrode active material comprising: A core comprising a lithium metal oxide as shown in the following chemical formula 1; and A shell containing metal sulfide particles adsorbed on the surface of the core. The average particle size of the metal sulfide particles is between 0.1 nm and 40 nm. [Chemical Formula 1] Li x [Ni y Co z Mr w M 1 v ]O u in, M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, and 0.

01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5; Wherein, based on the total weight of the positive electrode active material, the content of the metal sulfide particles is 0.1% to 2% by weight; The positive electrode active material particles are formed by preparing a mixture comprising the lithium metal oxide and the metal sulfide particles and heat-treating the mixture in the presence of one or more inert atmospheres selected from nitrogen and argon. The metal sulfide particles include single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al, or Ti.

2. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The metal sulfide particles are zinc sulfide (ZnS) particles.

3. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, Based on the total weight of the positive electrode active material, the content of the metal sulfide particles is from 0.3% to 1.5% by weight.

4. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The average particle size of the positive electrode active material is 0.5 μm to 10 μm.

5. The positive electrode active material for all-solid-state batteries as described in claim 1, wherein, The shell containing metal sulfide particles is adsorbed on more than 60% of the total area of ​​the core.

6. A method for manufacturing a positive electrode active material for an all-solid-state battery, the method comprising: Prepare a mixture comprising lithium metal oxide and metal sulfide particles as shown in Formula 1 below; and The mixture is heat-treated in the presence of one or more inert atmospheres selected from nitrogen and argon; The average particle size of the metal sulfide particles is between 0.1 nm and 40 nm. [Chemical Formula 1] Li x [Ni y Co z Mr w M 1 v ]O u in, M 1 It is one or more elements selected from the group consisting of: W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, and 0.

01. <z≤0.5、0.01<w≤0.5、0≤v≤0.2、1.5≤u≤4.5; The mixture contains 0.1% to 2% by weight of metal sulfides, based on the total weight of the lithium metal oxides. The metal sulfide particles include single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al, or Ti.

7. The method of claim 6, wherein, Based on the total weight of the lithium metal oxide, the mixture contains 0.3% to 1.5% by weight of metal sulfides.

8. The method of claim 6, wherein, The heat treatment is performed at 300°C to 500°C.

9. The method of claim 6, wherein, The metal sulfide particles are zinc sulfide (ZnS) particles.

10. An all-solid-state lithium secondary battery, comprising: A positive electrode comprising the positive electrode active material as described in claim 1; negative electrode; and A sulfide-based solid electrolyte is disposed between the positive electrode and the negative electrode.

11. The all-solid-state lithium secondary battery as described in claim 10, wherein, The sulfide-based solid electrolyte includes one or more selected from the group consisting of: Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5.

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