Sulfide-based positive electrode active materials for all-solid-state batteries

Abstract

The present invention relates to a cathode active material for an all-solid-state battery. The cathode active material has a structure in which a shell containing metal sulfide particles having a specific size is adsorbed on the surface of a core containing lithium metal oxide. This reduces cracks that may occur between the cathode active material and a solid electrolyte and the reactivity between them, thereby improving the mobility of lithium ions and achieving a high charge / discharge capacity.

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for a sulfide-based all-solid-state battery.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0127344, filed on September 27, 2021, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] All-solid-state lithium batteries use sulfide- or oxide-based solid electrolytes and can directly convert chemical energy into electrical energy by oxidizing or reducing lithium ions through the all-solid-state material. They offer advantages such as environmental friendliness, safety, and high-energy-density capacity storage. They can solve the limitations of currently available lithium secondary batteries, such as low energy density, high cost, and toxicity, and are therefore increasingly in demand as sustainable secondary batteries.

[0004] However, all-solid-state batteries are facing problems such as irreversibility due to side reactions at the interface between the sulfide-based or oxide-based solid electrolyte and the positive electrode during charge and discharge reactions, and a decrease in battery capacity due to interface resistance and uneven distribution of electrode charge due to space-charge layer formation. Furthermore, the low ionic conductivity of the all-solid-state material itself is hindering the commercialization of next-generation lithium all-solid-state batteries.

[0005] To solve these problems, positive electrode active materials using lithium metal sulfide as a medium have been developed. However, while the positive electrode active materials developed to date have significantly improved charge / discharge performance compared to oxide-based positive electrode active materials, they have a problem of very low capacity retention during charge / discharge compared to conventional oxide-based positive electrode active materials or negative electrode active materials.

[0006] In addition, a technology has been developed in which the surface of the positive electrode active material is treated with metal oxides and the like and applied to all-solid-state batteries, but this also has limitations in that the effect of improving charge / discharge performance is minimal, or although it does improve charge / discharge performance, it is not suitable for commercialization due to the high cost of the raw materials used. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent No. 10-1582394 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a sulfide-based cathode active material for an all-solid-state battery, which has improved lithium ion mobility by preventing cracks that may occur between the cathode active material and the solid electrolyte and by preventing side reactions from being induced between them. [Means for solving the problem]

[0009] To solve the above problems, In one embodiment, the present invention provides a core containing a lithium metal oxide represented by the following chemical formula 1; The metal sulfide particles (M 2 a shell containing The metal sulfide particles have an average particle size of 0.1 nm to 40 nm, and the positive electrode active material for an all-solid-state battery is provided as follows:

[0010] [Chemical formula 1] Li x [Ni y Co z Mn w M 1 v ]O u

[0011] In the above chemical formula 1, M 1 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 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である。

[0012] At this time, the metal sulfide particles (M 2 S) may include single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al, or Ti.

[0013] As an example, the metal sulfide particles (M 2 S) may be zinc sulfide (ZnS) particles.

[0014] The metal sulfide particles may be contained in an amount of 0.1 to 2% by weight based on the total weight of the positive electrode active material.

[0015] Furthermore, the positive electrode active material may have an average particle size of 0.5 μm to 10 μm.

[0016] Furthermore, the shell containing the metal sulfide particles can be adsorbed on an area of ​​60% or more based on the total area of ​​the core.

[0017] In one embodiment, the present invention provides: Lithium metal oxide and metal sulfide particles (M 2 S) and and heat treating the mixture, The present invention provides a method for producing a positive electrode active material for an all-solid-state battery, wherein the metal sulfide particles have an average particle size of 0.1 nm to 40 nm:

[0018] [Chemical formula 1] Li x [Ni y Co z Mnw M 1 v ]O u

[0019] In the above chemical formula 1, M 1 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 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である。

[0020] In this case, in the step of preparing the mixture, the mixture may contain 0.1 to 2 wt % of metal sulfide based on the total weight of the lithium metal oxide.

[0021] The heat treatment may be performed at 300° C. to 500° C. in the presence of at least one inert gas selected from nitrogen gas and argon gas.

[0022] In one embodiment, the present invention provides: a positive electrode containing the positive electrode active material according to the present invention; a negative electrode; and a sulfide-based solid electrolyte disposed between the positive electrode and the negative electrode.

[0023] In this case, the sulfide-based solid electrolyte may contain 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. [Effects of the Invention]

[0024] The cathode active material for an all-solid-state battery according to the present invention has a structure in which a shell containing metal sulfide particles having a specific size is adsorbed on the surface of a core containing lithium metal oxide, thereby reducing cracks that may occur between the cathode active material and the solid electrolyte and the reactivity therebetween, thereby improving the mobility of lithium ions and achieving a high charge / discharge capacity. DETAILED DESCRIPTION OF THE INVENTION

[0025] Although the present invention can be modified in various ways and can have various embodiments, specific embodiments will be described in detail.

[0026] However, this is not intended to limit the invention to any particular embodiment, but should be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0027] In the present invention, the terms "comprise" and "have" are intended to specify the presence of any feature, number, step, operation, component, part, or combination thereof described in the specification, and should be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0028] Furthermore, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion therebetween. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion therebetween. Furthermore, in this application, being "located on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0029] Furthermore, in the present invention, the term "major component" means 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 of the total weight of the composition or specific component, and in some cases, it can also mean 100% by weight when it constitutes the entire composition or specific component.

[0030] The present invention will now be described in more detail.

[0031] <Cathode active material for all-solid-state batteries> In one embodiment, the present invention provides a core containing lithium metal oxide; The metal sulfide particles (M 2 a shell containing The metal sulfide particles have an average particle size of 0.1 nm to 40 nm.

[0032] The positive electrode active material according to the present invention is used in a sulfide-based all-solid-state lithium secondary battery, and contains a lithium metal oxide core that exhibits electrical activity during charging and discharging of the battery, and a metal sulfide (M 2 S) The particles adsorb to form a shell.

[0033] Here, the lithium metal oxide may be any lithium metal oxide that reacts reversibly to provide lithium ions during charging and discharging of the battery, without any particular limitation. Specifically, the lithium metal oxide may contain a lithium metal oxide represented by the following Chemical Formula 1:

[0034] [Chemical formula 1] Li x [Ni y Co z Mn w M 1 v ]O u

[0035] In the above chemical formula 1, M 1is 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 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である。

[0036] The lithium metal oxide represented by the formula 1 is an oxide containing lithium and a transition metal, and may contain a high content of nickel among the transition metals. For example, the lithium metal oxide is 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. The lithium metal oxide contains a high content of nickel and is excellent in improving the charge / discharge capacity of the battery.

[0037] The core is made of metal sulfide (M 2 S) particles are adsorbed onto the surface, which reduces the interfacial resistance between the positive electrode active material and the solid electrolyte, improves the ability to resist side reactions between the positive electrode active material and the solid electrolyte, and suppresses the loss of lithium ions, thereby improving the electrical performance of the battery.

[0038] At this time, the metal sulfide (M 2 The S) particles are sulfide particles containing a transition metal, and specifically may be single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al, or Ti.

[0039] As an example, the metal sulfide particles (M 2 The positive electrode active material (S) may be particles containing zinc sulfide (ZnS) as a main component. Particles containing zinc sulfide as a main component have higher state stability than other metal sulfides, and can effectively suppress side reactions between the positive electrode active material and the sulfide-based solid electrolyte during charge and discharge of the battery. They also have the advantages of being easy to work with and economical.

[0040] The metal sulfide particles may be contained in an amount of 0.1 to 2 wt % relative to the total weight of the positive electrode active material, specifically, 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 % relative to the total weight of the positive electrode active material.

[0041] By controlling the content of metal sulfide particles contained in the positive electrode active material within the above range, the present invention can prevent a situation in which the content of metal sulfide particles is too low and the surface of the lithium metal oxide is not sufficiently surrounded, or an excessive amount of metal sulfide particles aggregates together and does not coat the surface of the lithium metal oxide.

[0042] Furthermore, the positive electrode active material may have an average particle size of 0.5 μm to 10 μm, and in this case, the metal sulfide particles located on the surface of the positive electrode active material may have an average particle size of 0.1 nm to 40 nm.

[0043] More specifically, the positive electrode active material may have an average particle size of 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 metal sulfide particles located on the surface of the positive electrode active material may have an average particle size of 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.

[0044] In the present invention, by controlling the average particle size of the positive electrode active material within the above range, the electrode activity of the positive electrode can be further improved, and by controlling the average particle size of the metal sulfide particles surrounding the core within the above range, the decrease in the electrical activity of the lithium metal oxide in the core can be minimized, side reactions at the interface with the solid electrolyte can be effectively suppressed, and cracks that may occur on the surface of the positive electrode active material can be prevented.

[0045] Furthermore, the shell containing the metal sulfide particles may surround at least 60% of the total surface of the core containing lithium metal oxide. Specifically, the metal sulfide particles may be physically and uniformly adsorbed to the surface of the core containing lithium metal oxide, rather than being chemically bonded. Here, the area adsorbed by the metal sulfide may be at least 60% of the core surface area, more specifically, at least 70%, at least 80%, at least 90%, at least 95%, or at least 98%. By controlling the area adsorbed by the shell containing lithium metal oxide to the above ratio, the present invention can effectively suppress side reactions between the positive electrode active material and the solid electrolyte without using an excessive amount of metal sulfide.

[0046] The cathode active material for an all-solid-state battery according to the present invention has a structure in which a shell containing metal sulfide particles having a specific size is adsorbed on the surface of a core containing lithium metal oxide, thereby reducing cracks that may occur between the cathode active material and the solid electrolyte and reactivity therebetween, thereby improving the mobility of lithium ions and realizing high charge / discharge capacity.

[0047] <Method of manufacturing positive electrode active material for all-solid-state batteries> In one embodiment, the present invention provides: Lithium metal oxide and metal sulfide particles (M 2 S) and and heat treating the mixture, The present invention provides a method for producing a positive electrode active material for an all-solid-state battery, wherein the metal sulfide particles have an average particle size of 0.1 nm to 40 nm:

[0048] [Chemical formula 1] Li x [Ni y Co z Mn w M 1 v ]O u

[0049] In the above chemical formula 1, M 1 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 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である。

[0050] The method for producing a positive electrode active material for an all-solid-state battery according to the present invention comprises the steps of: forming a core of a lithium metal oxide represented by Chemical Formula 1; and forming a shell of metal sulfide particles (M 2 This can be done by preparing a mixture containing S) and heat treating it.

[0051] Conventionally, the same method as the method for manufacturing a positive electrode active material in which an electrically active lithium metal oxide is used as a core and a shell containing a metal oxide is formed on the surface of the core, that is, metal sulfide (M 2 S) "Metal (M 2The metal chloride (M) and the sulfur source material (S) for providing the metal sulfide are mixed with the lithium metal oxide, and the metal sulfide (M) is then formed on the surface of the lithium metal oxide core. 2 The method for forming a shell containing metal sulfide (M S) is to form a shell containing a uniformly sized metal sulfide (M S) on a core containing lithium metal oxide. 2 However, the method for producing a positive electrode active material according to the present invention can uniformly form lithium metal oxide (M) particles contained in the core and metal sulfide (M) particles contained in the shell. 2 A core-shell cathode active material can be easily prepared by directly and uniformly mixing the S) particles and heat-treating the resulting mixture.

[0052] In this case, the step of preparing a mixture by mixing lithium metal oxide and metal sulfide particles may be performed using a dry mixer, a stirrer, a shaker such as an orbital shaker, a mortar mixer, a milling machine such as a planetary ball mill, or the like, which are used in the art for mixing powders of metal compounds, etc., but is not limited thereto.

[0053] For example, the step of preparing the mixture may be carried out using a planetary ball mill at a speed of 50 to 500 rpm per 1 kg of the mixture for 0.1 to 10 hours at a power of 1 to 100 kWh / 1 kg.

[0054] As another example, the step of preparing the mixture may be performed by mixing using a shaker for 1 to 10 hours, specifically for 2 to 8 hours.

[0055] In addition, in the mixture, the lithium metal oxide represented by Chemical Formula 1 is an oxide containing lithium and a transition metal, and may contain a high content of nickel among the transition metals. For example, the lithium metal oxide is LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi0.7 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.

[0056] In addition, the above metal sulfide (M 2 The S) particles are sulfide particles containing a transition metal, and specifically may be single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al, or Ti.

[0057] Furthermore, the above metal sulfide (M 2 The average particle size of S) may 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.

[0058] The mixture may also contain 0.1 to 2 wt % of metal sulfide relative to the total weight of the lithium metal oxide, and more specifically, the metal sulfide may be contained in an amount of 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 % relative to the total weight of the lithium metal oxide.

[0059] By controlling the content of the metal sulfide mixed with the lithium metal oxide within the above range, the present invention can prevent the content of the metal sulfide particles from being too low, which would result in the lithium metal oxide not being fully surrounded by the surface, or the excessive amount of metal sulfide from agglomerating together and not being coated on the surface of the lithium metal oxide.

[0060] Furthermore, the step of heat-treating the mixture containing lithium metal oxide and metal sulfide can be said to be a step of fixing the metal sulfide physically adsorbed on the surface of the lithium metal oxide core.

[0061] In this case, the heat treatment of the mixture can be carried out under the condition of an inert gas such as nitrogen gas, argon gas, or the like, either alone or in combination.

[0062] The heat treatment temperature may be 300°C or higher, and preferably 300°C to 480°C, 350°C to 500°C, 400°C to 500°C, or 420°C to 480°C.

[0063] In the present invention, by adjusting the heat treatment temperature of the mixture containing lithium metal oxide and metal sulfide within the above range, the metal sulfide can be easily fixed on the surface of the lithium metal oxide core without side reactions.

[0064] The method for producing a cathode active material for an all-solid-state battery according to the present invention can form a shell in which a metal sulfide is uniformly coated on the surface of a core containing a lithium metal oxide, and therefore has advantages such as excellent production efficiency of a cathode active material having a core-shell structure, easy control of the size of the metal sulfide to the nanometer level, and excellent processability.

[0065] <All-solid-state lithium secondary battery> Furthermore, in one embodiment, the present invention provides a positive electrode containing the positive electrode active material according to the present invention; a negative electrode; and a sulfide-based solid electrolyte disposed between the positive electrode and the negative electrode.

[0066] The all-solid-state lithium secondary battery according to the present invention includes a cathode containing the cathode active material according to the present invention described above, and not only is cracking at the interface between the cathode active material and the solid electrolyte significantly reduced, but side reactions are also suppressed, so that the battery can exhibit excellent lithium ion mobility in the electrode.

[0067] In this case, the positive electrode may have a structure in which a positive electrode mixture layer containing the above-described positive electrode active material of the present invention is formed on a positive electrode current collector.

[0068] The positive electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and may include, for example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like.

[0069] The positive electrode mixture layer contains a positive electrode active material, a conductive material, a binder, and a solid electrolyte, and may further contain an additive in some cases.

[0070] The positive electrode active material comprises a core containing a lithium metal oxide represented by the following chemical formula 1, and metal sulfide particles (M 2 and a shell containing S).

[0071] [Chemical formula 1] Li x [Ni y Co z Mn w M 1 v ]O u

[0072] In the above chemical formula 1, M 1 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 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である。

[0073] The lithium metal oxide may be any compound represented by Chemical Formula 1 without any particular limitation, and specifically, 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.

[0074] In addition, the above metal sulfide (M 2 The S) particles are sulfide particles containing a transition metal, and may specifically be single metal sulfides containing Zn, Mn, Cu, Cr, Zr, Al or Ti.

[0075] Furthermore, the above metal sulfide (M 2 The average particle size of S) may 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.

[0076] The average particle size of the positive electrode active material may 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.

[0077] Furthermore, the conductive material is not particularly limited as long as it has conductivity without inducing chemical changes in the battery. Specifically, graphite, carbon-based materials, metal powder or metal fiber, acicular or dendritic conductive whiskers, conductive metal oxides, conductive polymers, and any one or mixtures of these may be used. More specifically, examples of the conductive material include 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, thermal black, and carbon fiber; metal powders or fibers such as copper, nickel, aluminum, and silver; needle-shaped or dendritic 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 oxide, and conductive polymers such as polyphenylene derivatives. Any one or a mixture of two or more of these can be used.

[0078] The binder for the positive electrode is any one selected from the group consisting of N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), or a mixture of two or more thereof, N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), acrylonitrile The rubber may be any one selected from the group consisting of conjugated diene rubber latex such as styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), methyl methacrylate butadiene rubber (MBR), butadiene rubber (BR), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers, or a mixture of two or more of these.

[0079] Furthermore, the negative electrode may have a structure in which a negative electrode mixture layer containing a negative electrode active material is formed on a negative electrode current collector.

[0080] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity, and may include, for example, stainless steel, copper, nickel, titanium, baked carbon, or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like.

[0081] The negative electrode mixture layer contains a negative electrode active material, a conductive material, a binder, and a solid electrolyte, and may further contain an additive in some cases.

[0082] At this time, the negative electrode active material can be one selected from the group consisting of lithium metal, lithium alloy, lithium metal composite oxide, lithium-containing titanium composite oxide (LTO), and combinations thereof. Here, as the lithium alloy, 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 can be used. Further, the lithium metal composite oxide is any one metal (Me) oxide (MeOx) selected from the group consisting of lithium and Si, Sn, Zn, Mg, Cd, Ce, Ni, and Fe, and as an example, it may be LixFe2O3 (0 < x ≦ 1) or LixWO2 (0 < x ≦ 1).

[0083] Furthermore, as the negative electrode active material, metal composite oxides such as SnxMe1-xMe’yOz (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) can be used; 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 kinds.

[0084] Furthermore, examples of the conductive material include nickel powder, cobalt oxide, titanium oxide, carbon, etc. Examples of carbon include any one selected from the group consisting of ketjen black, acetylene black, furnace black, graphite, carbon fiber, and fullerene, or one or more of these.

[0085] The negative electrode binder is any one selected from the group consisting of N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), or a mixture of two or more thereof, N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), styrene The rubber may be any one selected from the group consisting of conjugated diene rubber latex such as butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), methyl methacrylate butadiene rubber (MBR), butadiene rubber (BR), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers, or a mixture of two or more of these.

[0086] Furthermore, the solid electrolyte contains sulfide-based particles, and the sulfide-based particles are an electrolyte for sulfide-based all-solid-state batteries. Those commonly used in the art can be applied, but specifically, one or more amorphous solid electrolytes 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 can be used.

[0087] The sulfide-based particles may have an average particle size of 0.1 μm to 50 μm, specifically, 0.1 μm to 10 μm. By controlling the average particle size of the sulfide-based particles constituting the solid electrolyte within the above range, the present invention can increase the porosity of the solid electrolyte and alleviate the problem of reduced battery capacity.

[0088] The present invention will be described in more detail below with reference to examples and experimental examples.

[0089] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0090] <Examples 1 to 5 and Comparative Examples 1 to 6. Production of cathode active materials for sulfide-based all-solid-state batteries> LiNi with an average particle size of 5±0.1μm 0.8 Co 0.1 Mn 0.1 Metal sulfide (M 2 S) were placed in a ball mill jar as shown in Table 1 below, and ball milling was carried out at a speed of 200±50 rpm for 1 hour with a power of 10 kWh / 1 kg to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 and metal sulfides (M 2 S) was uniformly mixed to obtain a mixture.

[0091] The mixture was transferred to an oven and heat-treated at 450±10°C for 2 hours to form the core LiNi 0.8 Co 0.1 Mn 0.1 Metal sulfides (M 2 As a result, a positive electrode active material (average particle size: 5±0.1 μm) uniformly coated with the nanoparticles (S) was obtained.

[0092] At this time, as shown in Table 1 below, when the content of metal sulfide is less than 0.1 wt % based on the total weight of lithium metal oxide, the core LiNi 0.8 Co 0.1 Mn0.1 It was confirmed that the surface of O2 was not sufficiently coated, and when the metal sulfide content exceeded 2 wt%, the metal sulfide particles aggregated together in the mixture, forming LiNi 0.8 Co 0.1 Mn 0.1 It was confirmed that O2 was not uniformly adsorbed on the surface.

[0093] [Table 1]

[0094] <Examples 6 to 10 and Comparative Examples 7 to 12. Production of sulfide-based all-solid-state batteries> Using the positive electrode active materials produced in Examples 1 to 5 and Comparative Examples 1 to 6, sulfide-based all-solid-state batteries were fabricated.

[0095] Specifically, the positive electrode active material prepared in each of the examples and comparative examples, sulfide-based solid electrolyte (LiS-P2S5), conductive material (carbon black), and binder (PVDF) were mixed in a weight ratio of 80:15:3:2, and the mixture was coated on an aluminum thin plate (thickness: 40 μm) and rolled at room temperature to prepare a positive electrode.

[0096] Separately, a lithium metal (Li) thin plate (thickness: 40 μm) was prepared as a negative electrode.

[0097] A solid electrolyte membrane (70 μm, 2.8 × 10) was placed between the prepared positive and negative electrodes. -3 S / cm, Li 10 SnP2S 12 ) was used to fabricate a sulfide-based all-solid-state battery.

[0098] [Table 2]

[0099] <Experimental Example> In order to evaluate the performance of the sulfide-based cathode active material for an all-solid-state battery according to the present invention, the following experiment was carried out.

[0100] a) Analysis of the cross-sectional structure of the positive electrode composite layer The sulfide-based all-solid-state batteries manufactured in Examples 6 to 10 and Comparative Examples 7 to 12 were prepared in a non-standby state, and their lifespans were extended under conditions of room temperature (25±1°C), 3.0 to 4.25 V, and 0.1 C. After that, each battery was disassembled, and the composite layer of the positive electrode was analyzed using a scanning electron microscope (SEM).

[0101] As a result, the battery of the embodiment of the present invention has a core made of lithium metal oxide (LiNi 0.8 Co 0.1 Mn 0.1 It was confirmed that the metal sulfide ZnS was uniformly adsorbed onto the surface of the lithium metal oxide (O2). This means that cracks were reduced at the interface between the lithium metal oxide contained in the core and the sulfide-based solid electrolyte, and side reactions were suppressed.

[0102] On the other hand, the comparative battery has a core made of lithium metal oxide (LiNi 0.8 Co 0.1 Mn 0.1 It was confirmed that cracks had occurred between the oxide (O2) and the sulfide-based solid electrolyte.

[0103] These results show that the positive electrode active material of the sulfide-based all-solid-state battery according to the present invention has a structure in which a shell containing metal sulfide particles of a specific size and a specific content is adsorbed on the surface of a core containing lithium metal oxide, and that cracks and side reactions are prevented from occurring between the lithium metal oxide core and the solid electrolyte.

[0104] b) Evaluation of initial charge / discharge performance The sulfide-based all-solid-state batteries manufactured in Examples 6 to 10 and Comparative Examples 7 to 12 were fixed in a jig inside a chamber at 60°C, and initial charge / discharge was performed under the condition of 0.1 C to measure the initial charge / discharge capacity and efficiency. At this time, the charge was performed by a constant current charge (CCC) method, and c / o was controlled to 0.5 C. The results are shown in Table 3 below.

[0105] [Table 3]

[0106] As shown in Table 3 above, it was confirmed that the cathode active material for a sulfide-based all-solid-state battery according to the present invention has a structure in which a shell containing metal sulfide particles having a specific size is adsorbed on the surface of a core containing lithium metal oxide, and thus has improved lithium ion mobility and high charge / discharge capacity.

[0107] These results demonstrate that the cathode active material for a sulfide-based all-solid-state battery according to the present invention reduces cracks and side reactions at the interface between the cathode active material and the solid electrolyte, and has excellent lithium ion mobility, thereby enabling high charge / discharge capacity.

[0108] Although the present invention has been described above with reference to preferred embodiments, it will be understood that a person skilled in the art or with ordinary knowledge in the art can make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as set forth in the claims below.

[0109] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims

1. a core containing a lithium metal oxide represented by the following chemical formula 1; The metal sulfide particles (M ２ a shell comprising The metal sulfide particles have an average particle size of 0.1 nm to 40 nm, [Chemical formula 1] Li ｘ [Ni ｙ Co ｚ Mn ｗ M １ ｖ ]O ｕ In the above Chemical Formula 1, M １ 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 each 1.0≦x≦1.30, 0.1≦y<0.95, 0.01<z≦0.5, 0.01<w≦0.5, 0≦v≦0.2, and 1.5≦u≦4.5, the metal sulfide particles are contained in an amount of 0.3 to 2 wt % based on the total weight of the positive electrode active material, the metal sulfide particles are uniformly coated on the surface of the core; The metal sulfide particles are a single metal sulfide containing Zn, Mn, Cu, Cr, Zr, Al or Ti.

2. 2. The positive electrode active material for a sulfide-based all-solid-state battery according to claim 1, wherein the metal sulfide particles are zinc sulfide (ZnS) particles.

3. 2. The cathode active material for a sulfide-based all-solid-state battery according to claim 1, wherein the average particle size of the cathode active material is 0.5 μm to 10 μm.

4. 2. The positive electrode active material for a sulfide-based all-solid-state battery according to claim 1, wherein the shell containing the metal sulfide particles is adsorbed to an area of ​​60% or more based on the area of ​​the entire core.

5. Lithium metal oxide and metal sulfide particles (M ２ S), and and heat treating the mixture, The metal sulfide particles have an average particle size of 0.1 nm to 40 nm, [Chemical formula 1] Li ｘ [Ni ｙ Co ｚ Mn ｗ M １ ｖ ]O ｕ In the above Chemical Formula 1, M １ 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 each 1.0≦x≦1.30, 0.1≦y<0.95, 0.01<z≦0.5, 0.01<w≦0.5, 0≦v≦0.2, and 1.5≦u≦4.5, the mixture comprises 0.1 to 2 wt. % of metal sulfide based on the total weight of lithium metal oxide; The method for producing a positive electrode active material for a sulfide-based all-solid-state battery, wherein the heat treatment is performed in the presence of at least one inert gas selected from the group consisting of nitrogen gas and argon gas.

6. The method for producing a positive electrode active material for a sulfide-based all-solid-state battery according to claim 5, wherein the heat treatment is performed at 300°C to 500°C.

7. A positive electrode comprising the positive electrode active material according to claim 1; a negative electrode; a sulfide-based solid electrolyte disposed between the positive electrode and the negative electrode.

8. 8. The all-solid-state lithium secondary battery according to claim 7, wherein the sulfide-based solid electrolyte comprises 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.

Images