Nano single-crystal positive electrode material and preparation method thereof, solid-state battery and electric equipment

Abstract

The invention provides a nano single-crystal positive electrode material and a preparation method thereof, a solid-state battery and electric equipment, and relates to the field of solid-state batteries. The nano single-crystal positive electrode material comprises an inner core and a coating layer arranged on the surface of the inner core, the chemical general formula of the inner core is LinNixCoyMnzAaBbO2, n is not less than 0.9 and not more than 1.2, x is not less than 0.8 and not more than 1.0, y is not less than 0 and not more than 0.2, z is not less than 0 and not more than 0.2, a is not less than 0.0004 and not more than 0.045, b is not less than 0.001 and not more than 0.018, and x + y + z + a + b is equal to 1; the general chemical formula of the coating layer is Lin 'XxO2, n' is not less than 0 and not more than 1, and x is not less than 0.33 and not more than 0.8; a comprises one or more of boron, yttrium, lanthanum, aluminum and phosphorus; b comprises one or more of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium and silicon; and X comprises one or more of niobium, cobalt, germanium, tin, antimony and cerium. Elements A and B inhibit particle contact, and the ion transmission efficiency is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of solid-state batteries, and in particular to a nano single crystal positive electrode material and a preparation method thereof, a solid-state battery and an electrical device. Background Art

[0002] Solid-state batteries are currently being widely researched in academia and industry due to their high energy density and excellent safety performance. However, the cathode materials used in solid-state batteries still suffer from problems such as small contact area, low contact quality, and poor interfacial cycling during use, which further limits their application.

[0003] In order to further improve the energy density of solid-state batteries and the interface contact between materials and solid electrolytes, nano-crystallization of positive electrode materials is a very suitable method. It can increase the contact area and contact quality between the material and the electrolyte, and can also improve the compaction density and energy density of the material by grading and blending with other positive electrode materials. However, the particle size of the precursor prepared by the current precursor co-precipitation method is about 2μm, and most of them are spherical in morphology, and it is impossible to continue to synthesize smaller precursors, which also limits the development and application of nano-single crystal materials. In addition, due to the reduction in particle size and the increase in specific surface area of ​​nano-single crystal materials, it also leads to serious residual lithium on the surface, which will further limit its application in the later battery cell end.

[0004] Based on this, there is an urgent need to provide a nano single crystal positive electrode material to solve the above problems. Summary of the Invention

[0005] The purpose of this application is to provide a nano single crystal positive electrode material and a preparation method thereof, a solid-state battery and an electrical device to solve the above problems.

[0006] To achieve the above objectives, the present application provides a nano single crystal positive electrode material in a first aspect, comprising a core and a coating layer disposed on the surface of the core; The chemical formula of the core is Li n Ni x Co y Mn z A a B b O2, where 0.9≤n≤1.2, 0.8≤x≤1.0, 0≤y≤0.2, 0≤z≤0.2, 0.0004<a≤0.045, 0.001<b≤0.018, x+y+z+a+b=1; The chemical formula of the coating layer is Li n' X x O2, where 0≤n'≤1, 0.33≤x≤0.8; Said A comprises one or more of boron, yttrium, lanthanum, aluminum and phosphorus; preferably one or more of boron, phosphorus and aluminum; The B includes one or more of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium and silicon; preferably one or more of zirconium, titanium, tungsten, niobium and aluminum; In order to obtain a beneficial combination effect, the combination of A and B is preferably one or more of boron and tungsten, boron and aluminum, or phosphorus and aluminum; The X includes one or more of niobium, cobalt, germanium, tin, antimony and cerium, preferably one or more of niobium, cobalt and cerium.

[0007] Optionally, the nano single crystal cathode material satisfies at least one of the following conditions: (1) The D50 of the nano single crystal positive electrode material is 0.1 μm-0.9 μm; (2) The D100 of the nano single crystal positive electrode material is 1.5 μm-4 μm; (3) The specific surface area of ​​the nano single crystal positive electrode material is 2m 2 / g-7m 2 / g; (4) The SPAN of the nano single crystal cathode material is 0.4-1.84; (5) The pH of the nano single crystal cathode material is 9-12; (6) The half-peak width of the nano single crystal positive electrode material is 0.165-0.305.

[0008] The second aspect of the present application provides a method for preparing the nano single crystal positive electrode material, comprising: A nickel source, a cobalt source, a manganese source, a lithium source, a compound containing a doping element A, and a compound containing a doping element B are mixed and sand-milled to obtain a mixture; Under an oxidizing atmosphere, the mixed material is subjected to a first sintering to obtain a first sintered material; In an oxidizing atmosphere, the first sintered material and the compound containing the coating element X are mixed and subjected to a second sintering to obtain a nano single crystal positive electrode material.

[0009] Optionally, the method for preparing the nano single crystal positive electrode material satisfies at least one of the following conditions: (1) The nickel source includes one or more of nickel oxide, nickel sulfide, nickel trioxide, high nickel matte, low nickel matte, nickel trioxide, nickel disulfide and nickel trisulfide; (2) The cobalt source includes one or more of cobalt oxide, cobalt carbonate, cobalt oxalate, cobalt trioxide and cobalt tetroxide; (3) The manganese source includes one or more of manganese monoxide, manganese dioxide, dimanganese trioxide and trimanganese tetraoxide; (4) The lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium fluoride, lithium oxide, lithium sulfide, lithium acetate and methyl lithium; (5) The compound containing the doping element A includes one or more of boric acid, boron trioxide, yttrium oxide, lanthanum oxide, aluminum phosphate and lithium phosphate; (6) The compound containing the doping element B includes one or more of the oxides, hydroxides, nitrates, sulfates, acetates, and carbonates of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium, and silicon; (7) The compound containing the coating element X includes one or more of the hydroxides, nitrates, sulfates, acetates and carbonates of niobium, cobalt, germanium, tin, antimony and cerium; (8) The molar ratio of Ni:Co:Mn:A:B in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 80-100:0-20:0-20:0.44-4.5, 0.1-1.8; (9) The molar ratio of lithium in the lithium source to the total transition metal in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 0.9-1.2:1; (10) The mass content of the compound containing the coating element X in the material subjected to the second sintering is 1000 ppm-8000 ppm.

[0010] Optionally, the method for preparing the nano single crystal positive electrode material satisfies at least one of the following conditions: (1) The stirring speed of the sand mill is 100 rpm-2500 rpm, the frequency is 5 Hz-50 Hz, the pumping times are 70 times / min-90 times / min, the solid content is 10%-80%, and the sand milling time is 1 hour-8 hours; (2) The D50 of the mixture is 0.005 μm-0.6 μm, and the D100 is 1.0 μm-1.7 μm.

[0011] Optionally, the first sintering includes low-temperature sintering and high-temperature sintering performed sequentially; The low-temperature sintering has a heating rate of 1°C / min-10°C / min, an end temperature of 250°C-500°C, and a constant temperature time of 1h-24h; The high-temperature sintering has a heating rate of 5°C / min-15°C / min, an end temperature of 510°C-800°C, a constant temperature time of 4h-24h, and an oxygen content of 90%-100%.

[0012] Optionally, the method for preparing the nano single crystal positive electrode material satisfies at least one of the following conditions: (1) During the first sintering and the second sintering, the flow rate of pure oxygen in the oxidizing atmosphere is independently 5 m / s. 3 / h-30m 3 / h; (2) The heating rate of the second sintering is 1°C / min-8°C / min, the end temperature is 510°C-700°C, the constant temperature time is 4h-24h, and the oxygen content is 90%-100%.

[0013] Optionally, before the second sintering, the first sintered material is washed, dried and crushed; The water washing temperature is 2°C-15°C, the time is 0.5min-10min, and the weight ratio of the first sintered material to the water is 0.5-2:1; The particle size of the pulverized product is 100 mesh to 500 mesh.

[0014] The third aspect of the present application provides a solid-state battery, comprising the nano single crystal positive electrode material or the nano single crystal positive electrode material prepared by the preparation method of the nano single crystal positive electrode material.

[0015] A fourth aspect of the present application provides an electrical device comprising the solid-state battery.

[0016] Compared with the prior art, the advantages of this application include: The nano single crystal positive electrode material provided by the present application introduces doping elements A and B that have a melting resistance effect, exerts a composite melting resistance effect, inhibits particle contact, effectively prevents agglomeration between nanoparticles, and provides high-temperature stability. In addition, the doping elements A and B can widen the ion channel, effectively improve the ion transmission efficiency of the nanoparticle material, improve the structural stability, and play a synergistic role between the melting resistance agent and the nano size; and the highly conductive coating layer provided on the surface of the nano single crystal, by introducing the X element, can form a lithium compound with the residual lithium on the surface, thereby improving the ionic conductivity; the hardness of the oxide that has not reacted with the residual lithium is relatively soft; and a 5-10nm thin layer of lithium compound is introduced between the sulfide electrolyte and the coating layer to block oxygen diffusion and improve contact with the sulfide solid electrolyte. On the one hand, it can increase the contact area between the surface of the nano single crystal positive electrode particle and the surface of the solid electrolyte positive electrode, reduce the side reaction of the material, and on the other hand, improve the particle transmission efficiency.

[0017] The present application provides a method for preparing a nano-single-crystal positive electrode material, in which a nano-mixture is obtained by sand milling. During the sand milling process, a compound containing dopant element A (melting inhibitor) and a compound containing dopant element B (melting inhibitor) can be uniformly dispersed in a precursor, so that each particle will be evenly isolated by the melting inhibitor during sintering, thereby forming a uniform particle size distribution. The nano-sized oxide obtained after sand milling is reacted with a lithium salt, thereby avoiding the agglomeration of hydroxides in traditional hydroxide precursors caused by dehydration during the sintering process, which makes it impossible to generate a nano-single-crystal positive electrode. In addition, by introducing melting inhibitors (compounds containing dopant element A and compounds containing dopant element B) to cover the particle surface to reduce direct contact, inhibit the formation of sintering necks, and promote uniform mixing of the lithium source and the precursor, a mixture with a uniform particle size distribution is obtained. This preparation method shortens the process flow, reduces production costs, and ensures the consistency of the precursor particle size, thereby realizing the preparation of nano-single-crystal positive electrode materials.

[0018] The solid-state battery and electrical equipment provided in this application have excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0020] Figure 1 This is an SEM image of the nano single crystal positive electrode material provided in Example 1; Figure 2 XRD pattern of the nano single crystal cathode material provided in Example 2; Figure 3 This is an SEM image of the positive electrode material provided in Comparative Example 5; Figure 4 The charge and discharge curves of the positive electrode materials prepared in Example 1 and Comparative Example 7 in a solid-state system are shown. DETAILED DESCRIPTION

[0021] First, the solution provided in this application is explained in more detail as follows: The minimum D50 size of the precursor currently prepared by conventional coprecipitation is around 2μm, and it is impossible to obtain nano-positive electrode materials using this precursor. Based on this, the present application obtains a mixture by sand-milling nickel, cobalt or manganese oxide in a single step, avoiding the agglomeration of hydroxides introduced by traditional hydroxide precursors during the sintering process due to dehydration, which prevents the formation of nano-single-crystal positive electrodes. In addition, by introducing a flux inhibitor, particle contact is suppressed, effectively preventing the agglomeration of nano-precursor particles, and forming the desired nano-single-crystal morphology. The specific scheme is as follows: The first aspect of the present application provides a nano single crystal positive electrode material, comprising a core and a coating layer disposed on the surface of the core; The chemical formula of the core is Li n Ni x Co y Mn z A a B b O2, where 0.9≤n≤1.2, 0.8≤x≤1.0, 0≤y≤0.2, 0≤z≤0.2, 0.0004<a≤0.045, 0.001<b≤0.018, x+y+z+a+b=1; Optionally, n may be 0.9, 1, 1.1, 1.2, or any value between 0.9 and 1.2; x may be 0.8, 0.9, 1, or any value between 0.8 and 1.0; z may be 0, 0.1, 0.2, or any value between 0 and 0.2; a may be 0.0004, 0.004, 0.01, 0.04, 0.045, or any value between greater than 0.0004 and less than or equal to 0.045; and b may be 0.002, 0.01, 0.018, or any value between greater than 0.001 and less than or equal to 0.018; The chemical formula of the coating layer is Li n' X x O2, where 0≤n'≤1, 0.33≤x≤0.8; Optionally, n' may be 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1, or any value between 0 and 1, and x may be 0.33, 0.5, 0.8, or any value between 0.33 and 0.8; The A comprises one or more of boron, yttrium, lanthanum, aluminum and phosphorus; The B includes one or more of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium and silicon; Preferably, B includes zirconium. Zirconium (Zr) is a high melting point element that can prevent agglomeration between nano-precursor particles, provide high temperature stability, and synergistically reduce sintering shrinkage. The X includes one or more of niobium, cobalt, germanium, tin, antimony and cerium.

[0022] It is important to note that, first, the compound formed by element X can improve ionic conductivity by forming lithium compounds with residual lithium on the surface; second, the hardness of the oxide that has not reacted with residual lithium is relatively soft; finally, a thin layer of lithium compound with a thickness of 5-10 nm is introduced between the sulfide electrolyte and the oxide coating to block oxygen diffusion and improve contact with the sulfide solid electrolyte; In some embodiments, the nano single crystal cathode material satisfies at least one of the following conditions: (1) The D50 of the nano single crystal positive electrode material is 0.1 μm-0.9 μm; Optionally, the D50 of the nano single crystal positive electrode material may be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or any value between 0.1 μm and 0.9 μm; (2) The D100 of the nano single crystal positive electrode material is 1.5 μm-4 μm; Optionally, the D100 of the nano single crystal positive electrode material may be 1.5 μm, 2 μm, 3 μm, 4 μm, or any value between 1.5 μm and 4 μm; (3) The specific surface area of ​​the nano single crystal positive electrode material is 2m 2 / g-7m 2 / g; Optionally, the specific surface area of ​​the nano single crystal cathode material can be 2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g or 2m 2 / g-7m 2 Any value between / g; (4) The SPAN of the nano single crystal cathode material is 0.4-1.84; Optionally, the SPAN of the nano single crystal positive electrode material may be 0.4, 0.5, 0.8, 1, 1.5, 1.84 or any value between 0.4 and 1.84; (5) The pH of the nano single crystal cathode material is 9-12; Optionally, the pH of the nano single crystal positive electrode material may be 9, 10, 11, 12 or any value between 9 and 12; (6) The half-peak width of the nano single crystal positive electrode material is 0.165-0.305.

[0023] Optionally, the half-value width of the nano single crystal positive electrode material can be 0.165, 0.2, 0.3, 0.305 or any value between 0.165-0.305.

[0024] It should be noted that the larger the half-peak width, the smaller the grain size; the half-peak width corresponding to conventional nano single crystals is 0.06-0.12.

[0025] In some embodiments, the nano-single-crystal cathode material comprises a bulk material.

[0026] The second aspect of the present application provides a method for preparing the nano single crystal positive electrode material, comprising: A nickel source, a cobalt source, a manganese source, a lithium source, a compound containing a doping element A, and a compound containing a doping element B are mixed and sand-milled to obtain a mixture; It should be noted that, first, sand milling can reduce the particle size and obtain nano-scale materials; second, the particles are depolymerized by mechanical force and evenly dispersed in the liquid phase. On the premise of obtaining nano-scale materials, compounds containing doping element A (melt retardant) and compounds containing doping element B (melt retardant) are introduced, so that the melt retardant can be evenly distributed in the gaps of the nano-materials during the sand milling process. When the melt retardant is water-soluble, wet mixing by sand milling can better disperse it. When the flux is non-water-soluble, the particle size of the melt retardant can be further reduced so that it can be evenly mixed with the material; finally, sand milling can increase the active sites on the particle surface and promote subsequent coating or chemical reaction. Under an oxidizing atmosphere, the mixed material is subjected to a first sintering to obtain a first sintered material; In an oxidizing atmosphere, the first sintered material and the compound containing the coating element X are mixed and subjected to a second sintering to obtain a nano single crystal positive electrode material.

[0027] In some embodiments, the method for preparing the nano single crystal cathode material satisfies at least one of the following conditions: (1) The nickel source includes one or more of nickel oxide, nickel sulfide, nickel trioxide, high nickel matte, low nickel matte, nickel trioxide, nickel disulfide and nickel trisulfide; (2) The cobalt source includes one or more of cobalt oxide, cobalt carbonate, cobalt oxalate, cobalt trioxide and cobalt tetroxide; (3) The manganese source includes one or more of manganese monoxide, manganese dioxide, dimanganese trioxide and trimanganese tetraoxide; (4) The lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium fluoride, lithium oxide, lithium sulfide, lithium acetate and methyl lithium; (5) The compound containing the doping element A includes one or more of boric acid, boron trioxide, yttrium oxide, lanthanum oxide, aluminum phosphate and lithium phosphate; (6) The compound containing the doping element B includes one or more of the oxides, hydroxides, nitrates, sulfates, acetates, and carbonates of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium, and silicon; (7) The compound containing the coating element X includes one or more of the hydroxides, nitrates, sulfates, acetates and carbonates of niobium, cobalt, germanium, tin, antimony and cerium; (8) The molar ratio of Ni:Co:Mn:A:B in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 80-100:0-20:0-20:0.44-4.5, 0.1-1.8; Optionally, the molar ratio of Ni in the nickel source, Co in the cobalt source, Mn in the manganese source, A in the compound containing the doping element A, and B in the compound containing the doping element B can be 80:0:0:0.44:0.1, 90:0:0:0.44:0.1, 100:0:0:0.44:0.1, 80:10:0:0.44:0.1, 80:20:0:0.44:0.1 : 0.1, 80:0:10:0.44:0.1, 80:0:20:0.44:0.1, 80:0:0:1:0.1, 80:0:0:4.5:0.1, 80:0:0:0.44:1, 80:0:0:0.44:1.8 or 80-100:0-20:0-20:0.44-4.5, any value between 0.1-1.8; It should be noted that when the doping element A is too much, the covering layer will be too thick, affecting the lithium ion transmission and reducing the capacity. When it is too little, it will not have the melting resistance effect. When the doping element B is too much, the capacity will be reduced. When it is too little, it will not have the effect of inhibiting the agglomeration of nanoparticles. (9) The molar ratio of lithium in the lithium source to the total transition metal in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 0.9-1.2:1; Optionally, the molar ratio of lithium in the lithium source to the total transition metal in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 0.9:1, 1:1, 1.1:1, 1.2:1, or any value between 0.9 and 1.2:1; (10) The mass content of the compound containing the coating element X in the material subjected to the second sintering is 1000-8000 ppm.

[0028] Optionally, the mass content of the compound containing the coating element X in the material undergoing the second sintering may be 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm or any value between 1000-8000 ppm.

[0029] In some embodiments, the method for preparing the nano single crystal cathode material satisfies at least one of the following conditions: (1) The stirring speed of the sand mill is 100 rpm-2500 rpm, the frequency is 5 Hz-50 Hz, the pumping times are 70 times / min-90 times / min, the solid content is 10%-80%, and the sand milling time is 1 hour-8 hours; Optionally, the stirring speed of the sand mill can be 100 rpm, 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm or any value between 100 rpm and 2500 rpm, the frequency can be 5 Hz, 10 Hz, 20 Hz, 30 Hz, 40 Hz, 50 Hz or any value between 5 Hz and 50 Hz, the pump frequency can be 70 times / min, 80 times / min, 90 times / min or any value between 70 times / min and 90 times / min, the solid content can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any value between 10% and 80%, and the sand milling time can be 1 h, 2 h, 4 h, 6 h, 8 h or any value between 1 h and 8 h; (2) The D50 of the mixture is 0.005 μm-0.6 μm, and the D100 is 1.0 μm-1.7 μm.

[0030] Optionally, D50 of the mixture may be 0.005 μm, 0.05 μm, 0.5 μm, 0.6 μm or any value between 0.005 μm and 0.6 μm, and D100 may be 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.7 μm or any value between 1.0 μm and 1.7 μm.

[0031] In some embodiments, the first sintering includes low-temperature sintering and high-temperature sintering performed sequentially; The low-temperature sintering has a heating rate of 1°C / min-10°C / min, an end temperature of 250°C-500°C, and a constant temperature time of 1h-24h; Optionally, the heating rate of low-temperature sintering can be 1°C / min, 2°C / min, 4°C / min, 6°C / min, 8°C / min, 10°C / min or any value between 1°C / min and 10°C / min, the end temperature can be 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or any value between 250°C and 500°C, and the constant temperature time can be 1h, 6h, 12h, 18h, 24h or any value between 1h and 24h; The high-temperature sintering has a heating rate of 5°C / min-15°C / min, an end temperature of 510°C-800°C, a constant temperature time of 4h-24h, and an oxygen content of 90%-100%.

[0032] Optionally, the heating rate of high-temperature sintering can be 5°C / min, 10°C / min, 15°C / min or any value between 5°C / min-10°C / min, the end temperature can be 510°C, 550°C, 600°C, 700°C, 800°C or any value between 510°C-800°C, the constant temperature time can be 4h, 6h, 12h, 18h, 24h or any value between 4h-24h, and the oxygen content can be 90%, 95%, 100% or any value between 90%-100%.

[0033] It should be noted that the low-temperature sintering is a pre-melting stage, which allows the precursor and lithium salt to be pre-fused, and the flux inhibitor to be evenly distributed between the precursors, avoiding rapid decomposition at high temperatures that may lead to material structure destruction or component segregation or the formation of large particle agglomerates, promoting the initial reaction of metal oxides and lithium sources to form initial crystals. If the temperature is too low, it cannot play a role of pre-fusion. If the temperature is too high, it may cause an imbalance in the stoichiometric ratio due to uneven diffusion of components. The high-temperature sintering is mainly to enhance the atomic diffusion capacity and fully develop the crystal structure. If the temperature is too low, a complete crystal form cannot be formed, and the grain boundary defects are serious. If the temperature is too high, overburning will occur, and the nano single crystal particles will melt to form large particles, and the nano single crystal morphology cannot be maintained.

[0034] In some embodiments, the method for preparing the nano single crystal cathode material satisfies at least one of the following conditions: (1) During the first sintering and the second sintering, the flow rate of pure oxygen in the oxidizing atmosphere is independently 5 m / s. 3 / h-30m 3 / h; Optionally, during the first sintering and the second sintering, the flow rate of pure oxygen in the oxidizing atmosphere can be independently 5m / s. 3 / h、10m 3 / h、15m 3 / h、20m 3 / h、25m 3 / h、30m 3 / h or 5m 3 / h-30m 3 Any value between / h; (2) The heating rate of the second sintering is 1°C / min-8°C / min, the end temperature is 510°C-700°C, the constant temperature time is 4h-24h, and the oxygen content is 90%-100%.

[0035] Optionally, the heating rate of the second sintering can be 1°C / min, 2°C / min, 4°C / min, 6°C / min, 8°C / min or any value between 1°C / min-8°C / min, the end temperature can be 510°C, 550°C, 600°C, 700°C or any value between 510°C-700°C, the constant temperature time can be 4h, 6h, 12h, 18h, 24h or any value between 4h-24h, and the oxygen content can be 90%, 95%, 100% or any value between 90%-100%.

[0036] In some embodiments, before the second sintering, the first sintered material is washed, dried and crushed; The water washing temperature is 2°C-15°C, the time is 0.5min-10min, and the weight ratio of the first sintered material to the water is 0.5-2:1; Optionally, the water washing temperature can be 2°C, 5°C, 10°C, 15°C, or any value between 2°C and 15°C; the washing time can be 0.5 min, 1 min, 2 min, 5 min, 10 min, or any value between 0.5 min and 10 min; and the weight ratio of the material to water after the first sintering can be 0.5:1, 1:1, 2:1, or any value between 0.5 and 2:1. It should be noted that water washing can reduce residual lithium on the surface of nanoparticle materials and improve the electrochemical properties of the materials. Since the materials are nanoscale, they have more exposed surfaces and are more likely to react with moisture and carbon dioxide in the air to generate residual lithium, which affects the material properties. The Li content in the coating layer can also be controlled by the degree of water washing. The degree of residual lithium removal can be controlled by the liquid-to-solid ratio, water washing time, water washing amount, and water washing temperature. Different amounts of residual lithium will form thin layers of lithium compounds with different coating thicknesses with the coating element X. A thin layer of lithium compound is introduced between the sulfide electrolyte and the oxide coating layer to block oxygen diffusion, improve contact with the sulfide solid electrolyte, and also improve lithium ion conductivity. The particle size of the pulverized product is 100 mesh to 500 mesh.

[0037] Optionally, the particle size of the pulverized product can be 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh or any value between 100 mesh and 500 mesh.

[0038] In some embodiments, the comminution process includes but is not limited to at least one of grinding, air flow crushing, vibration crushing, and mechanical crushing.

[0039] It should be noted that the material obtained after the first sintering has formed a nano-single crystal positive electrode material core, and there are multiple interaction forces between the atoms or molecules on its surface. High temperature intensifies the effects of these forces, causing the material to agglomerate at high temperature. The main purpose of crushing is to separate the agglomerated materials and obtain a positive electrode material core with a suitable particle size.

[0040] The third aspect of the present application provides a solid-state battery, comprising the nano single crystal positive electrode material or the nano single crystal positive electrode material prepared by the preparation method of the nano single crystal positive electrode material.

[0041] A fourth aspect of the present application provides an electrical device comprising the solid-state battery.

[0042] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0043] Example 1 This embodiment provides a method for preparing a nano single crystal positive electrode material. The specific preparation steps are as follows: S1: Nickel trioxide, cobalt oxide, manganese tetraoxide, boric acid and zirconium dioxide were added to reactor A at a molar ratio of Ni:Co:Mn:B:Zr of 95:3.9:1:1.8:0.25, and lithium carbonate was added at a molar ratio of Li:Me (total molar amount of transition metals in the nickel trioxide, cobalt oxide, manganese tetraoxide, boric acid and zirconium dioxide) of 1.03; S2: The above materials were sand-milled with a stirring speed of 1400 rpm, a sand mill frequency of 25 Hz, a pumping rate of 80 times / min, and a solid content of 30%. After sand-milling for 4 h, a precursor mixture with a D50 of 0.35 μm and a D100 of 1.25 μm was obtained; S3: Dry the precursor by double cone drying, control the double cone dryer temperature at 150 ° C, and dry for 4 hours; S4: Place the dried mixture in S3 in a pure oxygen atmosphere for secondary sintering. The pure oxygen flow rate is 15m 3 / h, the oxygen value in the furnace is 97%, firstly, the temperature is raised to 475℃ at a heating rate of 5℃ / min, and kept at this temperature for 5h, then the temperature is raised to 710℃ at a heating rate of 10℃ / min and kept at this temperature for 4h, and then the temperature is lowered at a cooling rate of 4℃ / min after the end of the holding period; S5: The material obtained in step 4 and water are put into a washing tank in a weight ratio of 0.5:1, the water temperature is controlled to 5°C, and the washing time is 2.5 minutes. Then, the material is centrifuged and dried in a centrifuge with a centrifugal frequency set to 25 Hz and a centrifugal time set to 30 minutes. Then, the material is double-cone dried with a drying temperature set to 150°C and a drying time set to 4 hours. After air flow crushing, the material is passed through a 325-mesh sieve; S6: Mix the sieved sample and niobium pentoxide, the mass content of niobium pentoxide in the mixture is 3000ppm, and place the mixture in a pure oxygen atmosphere for sintering. The pure oxygen flow rate is 5m 3 / h, the oxygen value in the furnace is 90%, the heating rate is 5℃ / min, the temperature is raised to 550℃ for reaction for 8h, the heating rate is 4℃ / min, the cooling rate is 3℃ / min, and the nano single crystal positive electrode material is obtained after air flow crushing through a 325 mesh sieve.

[0044] The SEM of the nano single crystal cathode material is as follows Figure 1 shown.

[0045] Example 2 This embodiment provides a method for preparing a nano single crystal positive electrode material. The specific preparation steps are as follows: S1: In reactor A, nickel hydroxide, cobalt trioxide, manganese dioxide, boric acid, and titanium dioxide were added in a molar ratio of Ni:Co:Mn:B:Ti of 95:4:1:1.8:0.5, and lithium carbonate was then added in a molar ratio of Li:Me (the total molar amount of transition metals in the above nickel hydroxide, cobalt oxide, manganese dioxide, boric acid, and titanium dioxide) of 1.015; S2: The above materials were sand-milled with a stirring speed of 2500 rpm, a sand mill frequency of 50 Hz, a pumping frequency of 90 times / min, and a solid content of 80%. After sand-milling for 8 h, a precursor mixture with a D50 of 0.6 μm and a D100 of 1.7 μm was obtained; S3: Dry the precursor by double cone drying, control the double cone dryer temperature at 350 ° C, and the drying time is 40 h; S4: Place the dried mixture in S3 in a pure oxygen atmosphere for secondary sintering. The pure oxygen flow rate is 30m 3 / h, the oxygen value in the furnace is 100%, firstly, the temperature is increased to 500℃ at a heating rate of 10℃ / min, and kept at this temperature for 1h, then the temperature is increased to 800℃ at a heating rate of 8℃ / min and kept at this temperature for 4h, and then the temperature is lowered at a cooling rate of 8℃ / min after the end of the holding period; S5: The material obtained in step 4 and water are put into a washing tank in a weight ratio of 2:1, the water temperature is controlled to 15°C, and the washing time is 10 minutes. Then, the material is centrifuged and dried in a centrifuge with a centrifugal frequency of 50 Hz and a centrifugal time of 60 minutes. Then, the material is double-cone dried with a drying temperature of 350°C and a drying time of 40 hours. After air flow crushing, the material is passed through a 500-mesh sieve; S6: Mix the sieved sample and cobalt tetroxide, the mass content of cobalt tetroxide in the mixture is 2000ppm, and place the mixture in a pure oxygen atmosphere for sintering. The pure oxygen flow rate is 5m 3 / h, the oxygen value in the furnace is 90%, the heating rate is 1℃ / min, the temperature is raised to 510℃ for reaction for 4h, the cooling rate is 3℃ / min, and the mixture is crushed by air flow and passed through a 500-mesh sieve to obtain a nano single crystal positive electrode material.

[0046] The XRD pattern of the nano single crystal cathode material is as follows: Figure 2 shown.

[0047] Example 3 This embodiment provides a method for preparing a nano single crystal positive electrode material. The specific preparation steps are as follows: S1: Nickel trioxide, cobalt trioxide, manganese monoxide, lanthanum oxide and zirconium dioxide were added to reactor A at a molar ratio of Ni:Co:Mn:La:Ca of 96:3.0:1:0.04:0.12, and lithium carbonate was added at a molar ratio of Li:Me (the total molar amount of transition metals in the nickel trioxide, cobalt oxide, manganese trioxide, boric acid and calcium oxide) of 1.005; S2: The above materials were sand-milled with a stirring speed of 100 rpm, a sand mill frequency of 5 Hz, a pumping rate of 70 times / min, and a solid content of 10%. After sand-milling for 1 hour, a precursor mixture with a D50 of 0.005 μm and a D100 of 1.0 μm was obtained; S3: Dry the precursor by double cone drying, control the double cone dryer temperature at 150 ° C, and dry for 4 hours; S4: Place the dried mixture in S3 in a pure oxygen atmosphere for secondary sintering. The pure oxygen flow rate is 5m 3 / h, the oxygen value in the furnace is 97%, firstly, the temperature is increased to 250℃ at a heating rate of 1℃ / min, and kept at this temperature for 1h, then the temperature is increased to 510℃ at a heating rate of 5℃ / min and kept at this temperature for 4h, and then the temperature is lowered at a cooling rate of 4℃ / min after the end of the holding period; S5: The material obtained in step 4 and water are put into a washing tank in a weight ratio of 0.5:1, the water temperature is controlled to 2°C, and the washing time is 0.5 min. Then, the material is centrifuged and dried in a centrifuge with a centrifugal frequency set to 25 Hz and a centrifugal time set to 30 min. Then, double cone drying is performed with a drying temperature set to 150°C and a drying time set to 4 h. After air flow crushing, the material is passed through a 100-mesh sieve; S6: Mix the sieved sample and cerium oxide, the cerium oxide content in the mixture is 1000ppm, and place the mixture in a pure oxygen atmosphere for sintering. The pure oxygen flow rate is 5m 3 / h, the oxygen value in the furnace was 90%, the heating rate was 1℃ / min, the temperature was raised to 510℃ for reaction for 4h, the cooling rate was 3℃ / min, and the material was crushed by air flow and passed through a 325-mesh sieve to obtain a nano single crystal positive electrode material.

[0048] Example 4 This embodiment provides a method for preparing a nano single crystal positive electrode material. The specific preparation steps are as follows: S1: Add nickel oxide, cobalt oxide, manganese monoxide, yttrium oxide and tungsten trioxide to reactor A at a molar ratio of Ni:Co:Mn:Y:W of 96:3:1:0.6:0.3, and then add lithium carbonate at a molar ratio of Li:Me (the total molar amount of transition metals in the above nickel trioxide, cobalt trioxide, manganese monoxide, yttrium oxide and tungsten trioxide) of 1.05; S2: The above materials were sand-milled with a stirring speed of 2500 rpm, a sand mill frequency of 50 Hz, a pumping rate of 90 times / min, and a solid content of 80%. After sand-milling for 1 hour, a precursor mixture with a D50 of 0.6 μm and a D100 of 1.7 μm was obtained; S3: Dry the precursor by double cone drying, control the double cone dryer temperature at 150 ° C, and dry for 4 hours; S4: Place the dried mixture in S3 in a pure oxygen atmosphere for secondary sintering. The pure oxygen flow rate is 30m 3 / h, the oxygen value in the furnace is 97%, firstly, the temperature is increased to 500℃ at a heating rate of 10℃ / min, and kept at this temperature for 24h, then the temperature is increased to 800℃ at a heating rate of 10℃ / min and kept at this temperature for 24h, and then the temperature is lowered at a cooling rate of 4℃ / min after the end of the holding period; S5: The material obtained in step 4 and water are put into a washing tank in a weight ratio of 2:1, the water temperature is controlled to 15°C, and the washing time is 10 minutes. Then, the material is centrifuged and dried in a centrifuge with a centrifugal frequency set to 25 Hz and a centrifugal time set to 30 minutes. Then, the material is double-cone dried with a drying temperature set to 150°C and a drying time set to 4 hours. After air flow crushing, the material is passed through a 100-mesh sieve; S6: Mix the sieved sample with antimony trioxide, with the mass content of niobic acid in the mixture being 8000ppm, and sinter the mixture in a pure oxygen atmosphere with a pure oxygen flow rate of 30m 3 / h, the oxygen value in the furnace is 90%, the heating rate is 8℃ / min, the temperature is raised to 700℃ for reaction for 24h, the cooling rate is 3℃ / min, and the mixture is crushed by air flow and passed through a 325-mesh sieve to obtain a nano single crystal positive electrode material.

[0049] Example 5 The difference from Example 1 is that this example does not perform the S5 water washing step, and the material obtained in Step 4 is directly mixed with niobium pentoxide for sintering.

[0050] Comparative Example 1 The difference from Example 1 is that the sand grinding treatment in step S2 is not performed, and the mixed material is directly placed in a pure oxygen atmosphere for two-stage sintering.

[0051] Comparative Example 2 The difference from Example 1 is that the order of adding boric acid and zirconium dioxide is changed, boric acid and zirconium dioxide are not added in step S1, and in step S4, boric acid and zirconium dioxide are mixed with the mixture dried in S3 to perform two-stage sintering.

[0052] Comparative Example 3 The difference from Example 1 is that niobium pentoxide is not added in step S6, and the sieved sample obtained in step S5 is directly sintered.

[0053] Comparative Example 4 The difference from Example 1 is that boric acid is not added in step S1.

[0054] Comparative Example 5 The difference from Example 1 is that zirconium dioxide is not added in step S1.

[0055] The SEM of the prepared cathode material is shown in Figure 2. Figure 3 shown.

[0056] Comparative Example 6 The difference from Example 1 is that zirconium dioxide and boric acid are not added in step S1.

[0057] Comparative Example 7 The difference from Example 1 is that the second stage sintering temperature in step S4 exceeds the set range. Specifically, the dried mixed material in step S3 is placed in a pure oxygen atmosphere for second stage sintering. The pure oxygen flow rate is 15m 3 / h, the oxygen value in the furnace is 97%, first increase the temperature to 650℃ at a heating rate of 5℃ / min, keep it warm for 1h, then increase the temperature to 950℃ at a heating rate of 10℃ / min and keep it warm for 4h, and then cool it down at a cooling rate of 4℃ / min after the insulation.

[0058] Comparative Example 8 The difference from Example 1 is that the second stage sintering time in step S4 exceeds the set range. Specifically, the dried mixed material in step S3 is placed in a pure oxygen atmosphere for second stage sintering. The pure oxygen flow rate is 30m 3 / h, the oxygen value in the furnace is 100%, first the temperature is raised to 500℃ at a heating rate of 5℃ / min, and kept warm for 30h, then the temperature is raised to 800℃ at a heating rate of 10℃ / min and kept warm for 40h, and then the temperature is lowered at a cooling rate of 8℃ / min after the insulation is completed.

[0059] The relevant data of the positive electrode materials prepared in the above examples and comparative examples are shown in Table 1.

[0060]

[0061] In addition, the charge and discharge curves of the positive electrode materials prepared in Example 1 and Comparative Example 7 in the solid state system are as follows: Figure 4 shown.

[0062] The positive electrode materials prepared in the above examples and comparative examples were respectively assembled with lithium-indium alloys into solid-state batteries, and electrochemical performance tests (0.1C charge capacity and discharge capacity at 1.9-3.7V) were performed. The specific results are shown in Table 2.

[0063] Table 2 Electrochemical performance test

[0064] analyze: From the results in Table 1 and Table 2, it can be seen from the comparison between Example 1 and Comparative Example 1 that the material obtained after directly mixing and sintering the materials is not a nano single crystal, and its performance in the solid-state battery is poor; the reason is that if sand grinding is not introduced, even if nano raw materials are selected for synthesis, it will bring about the problem of uneven mixing between the nano materials, resulting in the segregation of the main components in the subsequent synthesis process, and in severe cases, it may even be impossible to synthesize the required material.

[0065] By comparing Example 1 with Comparative Example 2, it can be found that the dispersion and anti-agglomeration effects of Example 1 are not as good as those of Example 1 due to the addition of flux at the end, the specific surface area is smaller, and the solid-state performance is not good; the reason is that one of the functions of the sanding process is to make the material dispersed evenly to avoid the local concentration of raw materials and additives, which affects the synthesis of the phase and the dispersion of the material.

[0066] Comparing Example 1 with Example 3, the performance of Example 3 is better by controlling the content of niobium pentoxide and lithium niobate. Controlling the amount of niobium pentoxide and lithium niobate is equivalent to introducing a thin layer of lithium compound between the sulfide electrolyte and the oxide coating layer, thereby blocking oxygen diffusion, improving contact with the sulfide solid electrolyte, and improving lithium ion conductivity.

[0067] Comparing Example 1 with Comparative Examples 4-6, the introduction of dual fluxes facilitates the formation of nanocrystals and enhances the performance of solid-state batteries. The dual fluxes also help create a better melting barrier between the nanomaterials, preventing particle agglomeration. Furthermore, the capacitance resistors are incorporated into the material lattice during high-temperature sintering, enhancing the material's ionic conductivity.

[0068] By comparing Example 1 with Comparative Examples 7-8, it can be found that appropriate sintering system control is conducive to the formation of nano-single crystals and the performance of their performance; if the sintering temperature is too low, it will lead to insufficient thermodynamics of the material and the inability to generate a suitable crystal form. If the sintering temperature is too high, it will lead to serious volatilization of the lithium salt and will also cause the nanoparticles to stick together severely at high temperatures and cannot be dispersed.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

[0070] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and to form distinct embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this application and should not be construed as an admission or any implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A nano single crystal cathode material, characterized in that: It comprises a core and a coating layer arranged on the surface of the core; The chemical formula of the core is Li n Ni x Co y Mn z A a B b O2, where 0.9≤n≤1.2, 0.8≤x≤1.0, 0≤y≤0.2, 0≤z≤0.2, 0.0004<a≤0.045, 0.001<b≤0.018, x+y+z+a+b=1; The chemical formula of the coating layer is Li n' X x O2, where 0≤n'≤1, 0.33≤x≤0.8; The A comprises one or more of boron, yttrium, lanthanum, aluminum and phosphorus; The B includes one or more of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium and silicon; The X includes one or more of niobium, cobalt, germanium, tin, antimony and cerium.

2. The nano single crystal cathode material according to claim 1, characterized in that At least one of the following conditions is met: (1) The D50 of the nano single crystal positive electrode material is 0.1 μm-0.9 μm; (2) The D100 of the nano single crystal positive electrode material is 1.5 μm-4 μm; (3) The specific surface area of ​​the nano single crystal positive electrode material is 2m 2 / g-7m 2 / g; (4) The SPAN of the nano single crystal cathode material is 0.4-1.84; (5) The pH of the nano single crystal cathode material is 9-12; (6) The half-peak width of the nano single crystal positive electrode material is 0.165-0.

305.

3. A method for preparing the nano single crystal positive electrode material according to claim 1 or 2, characterized in that: include: A nickel source, a cobalt source, a manganese source, a lithium source, a compound containing a doping element A, and a compound containing a doping element B are mixed and sand-milled to obtain a mixture; Under an oxidizing atmosphere, the mixed material is subjected to a first sintering to obtain a first sintered material; In an oxidizing atmosphere, the first sintered material and the compound containing the coating element X are mixed and subjected to a second sintering to obtain a nano single crystal positive electrode material.

4. The method for preparing a nano single crystal cathode material according to claim 3, characterized in that: At least one of the following conditions is met: (1) The nickel source includes one or more of nickel oxide, nickel sulfide, nickel trioxide, high nickel matte, low nickel matte, nickel trioxide, nickel disulfide and nickel trisulfide; (2) The cobalt source includes one or more of cobalt oxide, cobalt carbonate, cobalt oxalate, cobalt trioxide and cobalt tetroxide; (3) The manganese source includes one or more of manganese monoxide, manganese dioxide, dimanganese trioxide and trimanganese tetraoxide; (4) The lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium fluoride, lithium oxide, lithium sulfide, lithium acetate and methyl lithium; (5) The compound containing the doping element A includes one or more of boric acid, boron trioxide, yttrium oxide, lanthanum oxide, aluminum phosphate and lithium phosphate; (6) The compound containing the doping element B includes one or more of the oxides, hydroxides, nitrates, sulfates, acetates, and carbonates of zirconium, titanium, aluminum, magnesium, cobalt, tungsten, niobium, strontium, and silicon; (7) The compound containing the coating element X includes one or more of the hydroxides, nitrates, sulfates, acetates and carbonates of niobium, cobalt, germanium, tin, antimony and cerium; (8) The molar ratio of Ni:Co:Mn:A:B in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 80-100:0-20:0-20:0.44-4.5, 0.1-1.8; (9) The molar ratio of lithium in the lithium source to the total transition metals in the nickel source, the cobalt source, the manganese source, the compound containing the doping element A, and the compound containing the doping element B is 0.9-1.2:1; (10) The mass content of the compound containing the coating element X in the material subjected to the second sintering is 1000 ppm-8000 ppm.

5. The method for preparing a nano single crystal cathode material according to claim 3, characterized in that: At least one of the following conditions is met: (1) The stirring speed of the sand mill is 100 rpm-2500 rpm, the frequency is 5 Hz-50 Hz, the pumping times are 70 times / min-90 times / min, the solid content is 10%-80%, and the sand milling time is 1 hour-8 hours; (2) The D50 of the mixture is 0.005 μm-0.6 μm, and the D100 is 1.0 μm-1.7 μm.

6. The method for preparing a nano single crystal cathode material according to claim 3, characterized in that: The first sintering includes low-temperature sintering and high-temperature sintering performed sequentially; The low-temperature sintering has a heating rate of 1°C / min-10°C / min, an end temperature of 250°C-500°C, and a constant temperature time of 1h-24h; The high-temperature sintering has a heating rate of 5°C / min-15°C / min, an end temperature of 510°C-800°C, a constant temperature time of 4h-24h, and an oxygen content of 90%-100%.

7. The method for preparing a nano single crystal cathode material according to claim 3, characterized in that: At least one of the following conditions is met: (1) During the first sintering and the second sintering, the flow rate of pure oxygen in the oxidizing atmosphere is independently 5 m / s. 3 / h-30m 3 / h; (2) The heating rate of the second sintering is 1°C / min-8°C / min, the end temperature is 510°C-700°C, the constant temperature time is 4h-24h, and the oxygen content is 90%-100%.

8. The method for preparing a nano single crystal cathode material according to claim 3, wherein: Before the second sintering, the first sintered material is washed, dried and crushed; The water washing temperature is 2°C-15°C, the time is 0.5min-10min, and the weight ratio of the first sintered material to the water is 0.5-2:1; The particle size of the pulverized product is 100 mesh to 500 mesh.

9. A solid-state battery, characterized in that: The invention relates to a nano single crystal positive electrode material according to claim 1 or 2 or a nano single crystal positive electrode material prepared by the preparation method of the nano single crystal positive electrode material according to any one of claims 3 to 8.

10. An electrical device, characterized in that: Including the solid-state battery according to claim 9.

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