Modified ternary positive electrode material applied to all-solid-state battery, preparation method therefor, and all-solid-state battery

Abstract

A modified ternary positive electrode material applied to an all-solid-state battery. The modified ternary positive electrode material has a coated structure, comprising, in sequence from inside to outside, an inner core, an island-shaped inner coating layer, and a layered outer coating layer. The inner core is a ternary positive electrode material matrix, the island-shaped inner coating layer is crystalline LiaXbOc, and the layered outer coating layer is amorphous LiαYβOγ; the powder electronic conductivity of the material is 10-4-10-2S / cm. A preparation method for the modified ternary positive electrode material comprises: uniformly mixing the ternary positive electrode material matrix with an X-containing oxygen-containing compound, then performing high-temperature sintering processing, uniformly mixing the sintered product and a Y-containing oxygen-containing compound, and performing low-temperature sintering processing, to obtain a modified ternary positive electrode material which can be applied to an all-solid-state battery. Also disclosed is an all-solid-state battery. The inner coating layer and the outer coating layer of the modified ternary positive electrode material have ionic conductivity, which can promote the transmission of lithium ions between the positive electrode active material and a solid electrolyte, and reduce interface impedance.

Description

A modified ternary cathode material for all-solid-state battery, a preparation method thereof, and an all-solid-state battery

[0001] This application refers to Chinese patent application No. 202311769306.9 filed on December 20, 2023, entitled “A modified ternary positive electrode material for all-solid-state batteries, its preparation method and all-solid-state battery”, which is incorporated into this application in its entirety by reference. Technical Field

[0002] The present application relates to the field of batteries, and in particular to a modified ternary positive electrode material for use in all-solid-state batteries, a preparation method thereof, and an all-solid-state battery. Background Art

[0003] Lithium-ion batteries are already widely used in mobile consumer electronics, electric vehicles, and energy storage. However, traditional lithium-ion batteries contain flammable organic electrolytes, which have poor thermal stability at high temperatures. This poses a risk of thermal runaway, hindering the further development of electric vehicles. All-solid-state batteries (ASSBs), which replace traditional liquid organic electrolytes with solid electrolytes, significantly improve power battery safety and are a key technology for the next generation of power batteries.

[0004] Sulfide solid electrolytes have high ionic conductivity and have attracted widespread attention due to their ability to increase the energy density of batteries when paired with layered ternary cathode materials. However, sulfide solid electrolytes have a narrow electrochemical window, and a series of problems exist at the interface between them and layered ternary cathode materials, such as space charge layers and chemical / electrochemical side reactions. These problems lead to high interfacial impedance, hindering the transport of lithium ions at the interface and affecting the electrochemical performance of all-solid-state batteries. In addition, the cathode material undergoes repeated volume expansion and contraction during cycling, which can easily lead to contact failure at the interface between the solid electrolyte and the cathode material.

[0005] Coating is a commonly used surface modification technology that can improve the interfacial stability between materials. Traditional coating of positive electrode materials for liquid lithium-ion battery systems usually requires the coating to have good ionic and electronic conductivity to promote the conduction of lithium ions and electrons on the surface of the positive electrode material. However, the solid-solid interface between the positive electrode material and the sulfide solid electrolyte is different from the solid-liquid interface with the electrolyte. Studies have shown that coatings with higher electronic conductivity will accelerate the side reactions between the positive electrode material and the solid electrolyte, forming a high-impedance interface layer. However, the current coating methods for positive electrode materials for all-solid-state batteries mostly focus on improving the ionic conductivity of the material surface, and it is difficult to effectively suppress side reactions and space charge layer effects. Therefore, it is necessary to develop positive electrode materials for all-solid-state battery systems based on the characteristics of all-solid-state batteries. Summary of the Invention

[0006] The technical problem to be solved by this application is to overcome the deficiencies of the prior art and provide a modified ternary cathode material applied to all-solid-state batteries, its preparation method, and all-solid-state batteries.

[0007] To solve the above technical problems, the technical solution proposed in this application is as follows:

[0008] A modified ternary cathode material applied to all-solid-state batteries, the modified ternary cathode material has a coated structure, and the coated structure sequentially includes a core, an island-shaped inner coating layer, and a layered outer coating layer from the inside to the outside;

[0009] The core is a ternary cathode material matrix;

[0010] The island-shaped inner coating layer is crystalline Li a X b O c , where 0 < a ≤ 3, 0 < b ≤ 3, 0 < c ≤ 5, and the X element is selected from one or more of aluminum, titanium, vanadium, manganese, cobalt, yttrium, zirconium, niobium, lanthanum, cerium, tantalum, tungsten;

[0011] The layered outer coating layer is amorphous Li α Y β O γ , where 0 < α ≤ 4, 0 < β ≤ 4, 0 < γ ≤ 7, and the Y element is selected from one or more of boron, silicon, phosphorus, sulfur, titanium, vanadium, antimony, molybdenum, tungsten;

[0012] The powder electronic conductivity of the modified ternary cathode material is 10 -4 -10 -2 S / cm.

[0013] High-nickel ternary materials usually have a relatively high surface residual lithium content and need to be coated to remove the residual lithium. If all the Y elements of the outer coating layer are used to form an amorphous coating, the coating amount will be too large, resulting in an overly thick coating layer, which makes the electronic conductivity of the material too low and seriously hinders the progress of the electrochemical reaction. Therefore, this application first coats a crystalline intermediate coating layer to remove most of the residual lithium, and then coats an amorphous outer coating layer to adjust the electronic conductivity.

[0014] For the above-mentioned modified ternary cathode material, preferably, the chemical formula of the ternary cathode material matrix is LiNi x Co y Mn 1-x-y-z M z O2, 0.50 ≤ x < 1.00, 0 < y ≤ 0.3, 0 < 1 - x - y - z ≤ 0.3, 0 < z ≤ 0.02, where M is selected from one or more of magnesium, aluminum, calcium, titanium, vanadium, strontium, yttrium, zirconium, niobium, molybdenum, barium, lanthanum, cerium, tantalum, tungsten.

[0015] The modified ternary cathode material mentioned above, preferably, the crystalline Li a X b O c It is a lithium-containing compound with ion conductivity generated by the reaction of an oxygen-containing compound containing element X with residual lithium on the surface of the ternary positive electrode material.

[0016] The modified ternary cathode material mentioned above preferably has a specific surface area S of 0.1-2 m 2 / g.

[0017] The modified ternary cathode material mentioned above, preferably, the particle size of the island inner coating layer is 10-500nm; the content of the X element in the island inner coating layer in the modified ternary cathode material is wt X The ratio of the content of X element in the island inner coating layer to the specific surface area of ​​the modified ternary cathode material is 100-30000ppm. X / S is 10 3 -10 5 , the ratio unit is ppm m -2 g.

[0018] The modified ternary cathode material mentioned above, preferably, the amorphous Li α Y β O γ It is an amorphous lithium-containing compound with ionic conductivity and electronic insulation, which is generated by the reaction of an oxygen-containing compound containing the Y element with residual lithium on the surface of the ternary positive electrode material.

[0019] The modified ternary cathode material mentioned above, preferably, the thickness d of the layered outer coating layer is 1-30nm, and the ratio d / S of the thickness of the layered outer coating layer to the specific surface area of ​​the modified ternary cathode material is 1-100, and the ratio unit is nm m -2 g.

[0020] The modified ternary cathode material mentioned above, preferably, the content of the Y element in the layered outer coating layer in the modified ternary cathode material is wt Y The ratio of the Y element content to the specific surface area of ​​the modified ternary cathode material is 100-10000ppm. Y / S is 10 2 -10 4 , the unit of ratio is ppm m -2 g.

[0021] wt X and wt Y A large value of / S will lead to a decrease in the proportion of positive electrode active materials, resulting in a decrease in the material specific capacity; wt X and wt YIf the / S value is too low, the coating cannot effectively cover the surface of the positive electrode material particles and cannot achieve the effect of improving the interface properties.

[0022] As a general application concept, the present application also provides a method for preparing the above-mentioned modified ternary cathode material, comprising the following steps:

[0023] (1) uniformly mixing the ternary cathode material matrix and the oxygen-containing compound containing X;

[0024] (2) subjecting the mixture obtained in step (1) to a high-temperature sintering treatment, and after the sintering is completed, cooling, crushing, and screening the sintered product;

[0025] (3) uniformly mixing the sintered product after screening in step (2) and the oxygen-containing compound containing Y;

[0026] (4) The mixture obtained in step (3) is subjected to a low-temperature sintering treatment. After the sintering is completed, the sintered product is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for use in all-solid-state batteries.

[0027] In this preparation method, a high-temperature sintering treatment uses a relatively high sintering temperature to cause an oxygen-containing compound containing the X element to react with residual lithium on the surface of the ternary positive electrode material, thereby in situ generating an inner coating layer, which is a lithium-containing compound with ion conductivity. A low-temperature sintering treatment uses a relatively low sintering temperature to cause an oxygen-containing compound containing the Y element to react with residual lithium on the surface of the ternary positive electrode material, thereby in situ generating a layered outer coating layer, which is an amorphous, ionically conductive, and electronically insulating lithium-containing compound. At the same time, the electronic conductivity of the positive electrode material can be adjusted by controlling the composition, thickness, and coating amount of the outer coating layer.

[0028] In the preparation method of the modified ternary positive electrode material, preferably, in step (2), the high-temperature sintering temperature is 500-800°C, the sintering time is 1-15 hours, the high-temperature sintering is carried out in an oxygen or air atmosphere, and the heating rate before sintering is 1-10°C / min.

[0029] In the preparation method of the modified ternary positive electrode material mentioned above, preferably, in step (4), the temperature of the low-temperature sintering treatment is 200-500°C, the sintering time is 1-15 hours, the low-temperature sintering is carried out in an oxygen or air atmosphere, and the heating rate before sintering is 1-10°C / min.

[0030] In the above-mentioned method for preparing the modified ternary cathode material, preferably, in step (2) and step (4), the mixing method is high-speed stirring, the speed of high-speed stirring is 100 to 2500 rpm, and the time of high-speed stirring is 10 to 60 minutes.

[0031] As a general application concept, the present application also provides an all-solid-state battery, the positive electrode material used in the all-solid-state battery is the above-mentioned modified ternary positive electrode material or the modified ternary positive electrode material prepared by the above-mentioned preparation method.

[0032] Compared with the prior art, the advantages of this application are:

[0033] (1) The modified ternary cathode material of the present application comprises, from the inside to the outside, a core, an island-shaped inner coating layer and a layered outer coating layer, wherein the inner coating layer is a crystalline Li a X b O c The outer coating layer is amorphous Li α Y β O γ Both the inner coating layer and the outer coating layer have ionic conductivity, which can promote the transmission of lithium ions between the positive electrode active material and the solid electrolyte and reduce the interface impedance; and the outer coating layer is amorphous and has a certain elasticity. It can act as a buffer layer when attached to the surface of the material particles, alleviating the strain caused by repeated expansion and contraction during the charge and discharge cycle of the material, and maintaining good solid-solid interface contact between the positive electrode active material and the solid electrolyte.

[0034] (2) The outer coating layer in the modified ternary positive electrode material of the present application also has electronic insulation properties. The coating amount and thickness of the outer coating layer are adjusted according to the specific surface area of ​​the material, and the electronic conductivity of the material is controlled within an appropriate range. This can not only inhibit the interfacial side reactions between the space charge layer and the positive electrode material and the solid electrolyte, improve the interfacial compatibility between the positive electrode material and the solid electrolyte, but also improve the stability and electrochemical performance of the positive electrode active material in the all-solid-state battery system; moreover, the layered coating morphology of the outer coating layer can evenly cover the surface of the positive electrode material, greatly reducing the direct contact between the positive electrode material and the solid electrolyte, thereby avoiding interfacial side reactions.

[0035] (3) The modified ternary cathode material of the present application is prepared using a step-by-step sintering method, which enables the modified ternary cathode material to exhibit high specific capacity and high cycle retention rate in a sulfide solid-state battery system.

[0036] (4) The preparation method of the present application can effectively reduce the residual lithium content on the surface of the ternary positive electrode material while forming a coating layer; and the preparation method uses a dry coating process, which is low in cost, compatible with existing production equipment, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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 of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0038] FIG1 is an XRD image of the modified ternary cathode material for all-solid-state batteries prepared in Example 1 of the present application.

[0039] Figure 2 is an SEM image of the modified ternary positive electrode material for all-solid-state batteries prepared in Example 1 of the present application.

[0040] Figure 3 is a TEM image of the modified ternary positive electrode material for all-solid-state batteries prepared in Example 1 of the present application.

[0041] Figure 4 is an SEM image of the modified ternary positive electrode material for all-solid-state batteries prepared in Example 4 of the present application.

[0042] Figure 5 is an SEM image of the modified ternary positive electrode material for all-solid-state batteries prepared in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0043] To facilitate understanding of the present application, the present application will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the scope of protection of the present application is not limited to the following specific embodiments.

[0044] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this application.

[0045] Unless otherwise specified, all reagents and raw materials used in this application are commercially available products or products that can be prepared by known methods.

[0046] Example 1:

[0047] The modified ternary cathode material used in the all-solid-state battery in this embodiment is a coated structure, which includes a core, an island-shaped inner coating layer and a layered outer coating layer from the inside to the outside. The core is the ternary cathode material matrix LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01O2, the island-shaped inner coating layer is a crystalline lithium-containing compound LiNbO3, which is generated by the reaction of Nb2O5 with the residual lithium on the surface of the ternary positive electrode material. The particle size of the island-shaped inner coating layer is about 50nm, and the layered outer coating layer is an amorphous lithium-containing compound Li2WO4, which is generated by the reaction of H2WO4 with the residual lithium on the surface of the ternary positive electrode material. The specific surface area S of the modified ternary positive electrode material is 0.48m 2 / g, and the electronic conductivity is 2.6×10 -3 S / cm.

[0048] The method for preparing the modified ternary cathode material for all-solid-state batteries of this embodiment comprises the following steps:

[0049] (1) Weigh 10 kg of ternary cathode material LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01 O2 was added into a high-speed mixer, and 10,000 ppm of Nb2O5 was added based on the Nb content. The mixture was stirred at a speed of 800 rpm for 30 minutes in the high-speed mixer to mix evenly.

[0050] (2) The mixture obtained in step (1) was heated to 650°C at a heating rate of 5°C / min in an oxygen atmosphere and sintered for 12 hours. After sintering, the mixture was cooled, crushed, and sieved.

[0051] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Add 3000 ppm of H2WO4 based on the W content and stir at 1200 rpm for 25 minutes in the high-speed mixer to mix evenly.

[0052] (4) The mixture obtained in step (3) is heated to 400°C at a heating rate of 2°C / min in an oxygen atmosphere and sintered at this temperature for 5 hours. After sintering, the mixture is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for all-solid-state batteries.

[0053] The XRD pattern of the modified ternary positive electrode material for all-solid-state batteries prepared in this embodiment is shown in Figure 1, which is consistent with the diffraction peak of the standard ternary positive electrode material and has no impurity peak; its SEM pattern is shown in Figure 2, from which it can be seen that the D50 particle size of the modified ternary positive electrode material particles is 3.9μm, and the surface is covered with nano-scale coating particles; the TEM pattern is shown in Figure 3, from which it can be seen that the interior of the material is a ternary positive electrode material matrix, the size of the inner coating layer particles is about 50nm, and the outside is covered with a uniform outer coating layer with a thickness of about 21nm. In the TEM pattern, the outer coating layer has no lattice fringes and is amorphous.

[0054] ICP was used to detect the contents of Nb and W in the modified ternary cathode material prepared in this example. The Nb content (wt%) was X 9578ppm, W element content wt Y 2893ppm, wt X / S is 2.0×10 4 ppm m -2 g,wt Y / S is 6.0×10 3 ppm m -2 g; The thickness of the outer coating layer d is 21nm, and the ratio of the thickness of the outer coating layer d to the specific surface area of ​​the modified ternary cathode material d / S is 44, and the unit of the ratio is nm m -2 The residual lithium content on the surface of the core ternary material matrix is ​​4235ppm. After coating modification, the residual lithium content on the surface of the material is reduced to 1247ppm.

[0055] Example 2:

[0056] The modified ternary cathode material used in the all-solid-state battery in this embodiment is a coated structure, which includes a core, an island-shaped inner coating layer and a layered outer coating layer from the inside to the outside. The core is a ternary cathode material LiNi 0.65 Co 0.15 Mn 0.195 Mg 0.005 O2, the island-shaped inner coating layer is a crystalline lithium-containing compound Li2TiO3 and Li2ZrO3, which is generated by the reaction of TiO2, ZrO2 and the residual lithium on the surface of the ternary positive electrode material. The particle size of the island-shaped inner coating layer is 80nm, and the layered outer coating layer is an amorphous lithium-containing compound Li3PO4, which is generated by the reaction of NH4H2PO4 and the residual lithium on the surface of the ternary positive electrode material. The specific surface area S of the modified ternary positive electrode material is 0.57m 2 / g, and the electronic conductivity is 4.7×10 -3 S / cm.

[0057] The method for preparing the modified ternary cathode material for all-solid-state batteries of this embodiment comprises the following steps:

[0058] (1) Weigh 10 kg of ternary cathode material LiNi 0.65 Co 0.15 Mn 0.195 Mg 0.005 O2 was added into a high-speed mixer, and based on the Ti and Zr contents, 5000 ppm of TiO2 and 3000 ppm of ZrO2 were added, and the mixture was stirred at a speed of 1000 rpm for 40 minutes in the high-speed mixer to mix evenly.

[0059] (2) The mixture obtained in step (1) was heated to 700°C at a heating rate of 3°C / min in an oxygen atmosphere and sintered for 12 hours. After sintering, the mixture was cooled, crushed, and sieved.

[0060] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Add 2500 ppm of NH4H2PO4 based on the phosphorus content and stir at 600 rpm for 60 minutes in the high-speed mixer to mix evenly.

[0061] (4) The mixture obtained in step (3) is heated to 350°C at a heating rate of 5°C / min in an oxygen atmosphere and sintered at this temperature for 8 hours. After sintering, the mixture is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for use in all-solid-state batteries.

[0062] The Ti, Zr and P contents in the modified ternary cathode material were detected by ICP. The Ti content was 4824ppm, the Zr content was 2821ppm and the P content was 2453ppm. The ratio of the total content of Ti and Zr elements in the intermediate coating layer to the specific surface area of ​​the modified ternary cathode material was wt%. X / S is 1.3×10 4 ppm m -2 g, the ratio of the P content in the outer coating layer to the specific surface area of ​​the modified ternary cathode material wt Y / S is 4.3×10 3 ppm m -2 g; The thickness of the outer coating layer d is 14 nm, and the ratio of the thickness of the outer coating layer d to the specific surface area of ​​the modified ternary cathode material d / S is 25, and the unit of the ratio is nm m -2 The residual lithium content on the surface of the core ternary material matrix is ​​2683ppm, while the residual lithium content on the surface of the modified material is only 849ppm.

[0063] Example 3:

[0064] The modified ternary cathode material used in the all-solid-state battery in this embodiment is a coated structure, which includes a core, an island-shaped inner coating layer and a layered outer coating layer from the inside to the outside. The core is a ternary cathode material LiNi 0.90 Co 0.05 Mn 0.04 Zr 0.01O2, the inner coating layer is a crystalline lithium-containing compound Li3WO4 and LiAlO2, which is generated by the reaction of W2O5, Al(OH)3 and the residual lithium on the surface of the ternary positive electrode material. The particle size of the inner coating layer is 70nm, and the outer coating layer is an amorphous lithium-containing compound Li2B4O7 and Li2MoO4, which is generated by the reaction of B2O3, MoO3 and the residual lithium on the surface of the ternary positive electrode material. The specific surface area S of the modified ternary positive electrode material is 0.62m 2 / g, and the electronic conductivity is 6.3×10 -4 S / cm.

[0065] The method for preparing the modified ternary cathode material for all-solid-state batteries of this embodiment comprises the following steps:

[0066] (1) Weigh 10 kg of ternary cathode material LiNi 0.90 Co 0.05 Mn 0.04 Zr 0.01 O2 was added into a high-speed mixer, and based on the Sr and Al contents, 2000 ppm of W2O5 and 10000 ppm of Al(OH)3 were added, and the mixture was stirred at a speed of 1800 rpm for 30 minutes in the high-speed mixer to mix evenly.

[0067] (2) The mixture obtained in step (1) was heated to 500° C. at a heating rate of 2° C. / min in an oxygen atmosphere and sintered for 12 h. After sintering, the mixture was cooled, crushed, and sieved.

[0068] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Based on the B and Mo contents, add 2000 ppm of B2O3 and 3000 ppm of MoO3. Stir the mixture in the high-speed mixer at 900 rpm for 45 minutes to mix evenly.

[0069] (4) The mixture obtained in step (3) is heated to 500°C at a heating rate of 10°C / min in an oxygen atmosphere and sintered at this temperature for 9 hours. After sintering, the mixture is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for all-solid-state batteries.

[0070] The W, Al, Mo and B contents in the modified ternary cathode material were detected by ICP. The W content was 1835ppm, the Al content was 9247ppm, the B content was 1887ppm and the Mo content was 2749ppm. The ratio of the total content of W and Al elements in the inner coating layer to the specific surface area of ​​the modified ternary cathode material was wt. X / S is 1.8×10 4 ppm m -2g, the ratio of the total content of B and Mo elements in the outer coating layer to the specific surface area of ​​the modified ternary cathode material wt Y / S is 7.5×10 3 ppm m -2 g; The thickness of the outer coating layer d is 30nm, and the ratio of the thickness of the outer coating layer d to the specific surface area of ​​the modified ternary cathode material d / S is 48, and the ratio unit is nm m -2 The residual lithium content on the surface of the core ternary material matrix is ​​4846 ppm, and the residual lithium content on the surface after coating modification is 1874 ppm.

[0071] Example 4:

[0072] The modified ternary cathode material used in the all-solid-state battery in this embodiment is a coated structure, which includes a core, an island-shaped inner coating layer and a layered outer coating layer from the inside to the outside. The core is a ternary cathode material LiNi 0.83 Co 0.11 Mn 0.05 W 0.01 O2, the inner coating layer is a crystalline lithium-containing compound LiTaO3 and LiVO3, which is generated by the reaction of Ta2O5, V2O5 and the residual lithium on the surface of the ternary positive electrode material. The particle size of the inner coating layer is 120nm, and the outer coating layer is an amorphous lithium-containing compound LiNbO3 and Li2ZrO3, which is generated by the reaction of Nb2O5, ZrO2 and the residual lithium on the surface of the ternary positive electrode material. The specific surface area S of the modified ternary positive electrode material is 0.54m 2 / g, and the electronic conductivity is 8.2×10 -3 S / cm.

[0073] The method for preparing the modified ternary cathode material for all-solid-state batteries of this embodiment comprises the following steps:

[0074] (1) Weigh 10 kg of ternary cathode material LiNi 0.83 Co 0.11 Mn 0.05 W 0.011 O2 was added into a high-speed mixer, and based on the Ta and V contents, 8000 ppm of Ta2O5 and 2000 ppm of V2O5 were added, and the mixture was stirred at a speed of 1200 rpm for 50 minutes in the high-speed mixer to mix evenly.

[0075] (2) The mixture obtained in step (1) was heated to 550°C at a heating rate of 5°C / min in an oxygen atmosphere and sintered for 15 hours. After sintering, the mixture was cooled, crushed, and sieved.

[0076] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Based on the Nb and Zr contents, add 1000 ppm of Nb2O5 and 500 ppm of ZrO2. Stir the mixture in a high-speed mixer at 800 rpm for 45 minutes to mix evenly.

[0077] (4) The mixture obtained in step (3) is heated to 450°C at a heating rate of 4°C / min in an oxygen atmosphere and sintered for 6 hours. After sintering, it is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for all-solid-state batteries.

[0078] The SEM image of the modified ternary cathode material for all-solid-state batteries prepared in this embodiment is shown in FIG4 . As can be seen from FIG4 , the cathode material is a secondary spherical particle formed by the agglomeration of primary particles, with a D50 particle size of 4.7 μm and a surface covered with nano-scale coated particles.

[0079] The contents of Ta, V, Nb and Zr in the modified ternary cathode material were detected by ICP. The Ta content was 7847ppm, the V content was 1926ppm, the Nb content was 958ppm and the Zr content was 493ppm. The ratio of the total content of Ta and V in the inner coating layer to the specific surface area of ​​the modified ternary cathode material was wt%. X / S is 1.8×10 4 ppm m -2 g, the ratio of the total content of Nb and Zr elements in the outer coating layer to the specific surface area of ​​the modified ternary cathode material wt Y / S is 2.7×10 3 ppm m -2 g; The thickness of the outer coating layer d is 8nm, and the ratio of the thickness of the outer coating layer d to the specific surface area of ​​the modified ternary cathode material d / S is 15, and the ratio unit is nm m -2 The residual lithium content on the surface of the core ternary material matrix is ​​3872ppm, and the residual lithium content on the surface of the material after coating modification is 1357ppm.

[0080] Comparative Example 1:

[0081] The modified ternary cathode material used in the all-solid-state battery in this comparative example is a coated structure, which includes a core, an intermediate coating layer and an outer coating layer from the inside to the outside. The core is the ternary cathode material matrix LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01O2, the middle coating layer is a crystalline lithium-containing compound LiNbO3, the particle size of the middle coating layer is about 50nm, and the outer coating layer is a crystalline lithium-containing compound Li2WO4. The specific surface area S of the modified ternary positive electrode material is 0.53m 2 / g, and the electronic conductivity is 3.2×10 -2 S / cm.

[0082] The preparation method of the modified ternary cathode material for all-solid-state batteries of this comparative example comprises the following steps:

[0083] (1) Weigh 10 kg of ternary cathode material LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01 O2 was added into a high-speed mixer, and 10,000 ppm of Nb2O5 was added based on the Nb content. The mixture was stirred at a speed of 800 rpm for 30 minutes in the high-speed mixer to mix evenly.

[0084] (2) The mixture obtained in step (1) was heated to 650°C at a heating rate of 5°C / min in an oxygen atmosphere and sintered for 12 hours. After sintering, the mixture was cooled, crushed, and sieved.

[0085] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Add 3000 ppm of H2WO4 based on the W content and stir at 1200 rpm for 25 minutes in the high-speed mixer to mix evenly.

[0086] (4) The mixture obtained in step (3) is heated to 650°C at a heating rate of 2°C / min under an oxygen atmosphere and sintered at this temperature for 5 hours. After sintering, the mixture is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for all-solid-state batteries.

[0087] ICP was used to detect the contents of Nb and W in the modified ternary cathode material prepared in this example. The Nb content (wt%) was X 9684ppm, W element content wt Y 2738ppm, wt X / S is 1.8×10 4 ppm m -2 g,wt Y / S is 5.2×10 3 ppm m -2 The outer coating layer has a particle size of approximately 80 nm. The residual lithium content on the surface of the core ternary material matrix is ​​4235 ppm, and after coating modification, the residual lithium content on the surface is 1478 ppm.

[0088] Comparative Example 2:

[0089] The modified ternary cathode material used in the all-solid-state battery in this comparative example is a coated structure, which includes a core, an intermediate coating layer and an outer coating layer from the inside to the outside. The core is a ternary cathode material LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01 O2, the middle coating layer is a crystalline lithium-containing compound LiNbO3, the particle size of the middle coating layer is about 50nm, and the outer coating layer is an amorphous lithium-containing compound Li2WO4. The specific surface area S of the modified ternary positive electrode material is 0.45m 2 / g, and the electronic conductivity is 2.2×10 -2 S / cm.

[0090] The preparation method of the modified ternary cathode material for all-solid-state batteries of this comparative example comprises the following steps:

[0091] (1) Weigh 10 kg of ternary cathode material LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01 O2 was added into a high-speed mixer, and 400 ppm of Nb2O5 was added based on the Nb content. The mixture was stirred at a speed of 800 rpm for 30 minutes in the high-speed mixer to mix evenly.

[0092] (2) The mixture obtained in step (1) was heated to 650°C at a heating rate of 5°C / min in an oxygen atmosphere and sintered for 12 hours. After sintering, the mixture was cooled, crushed, and sieved.

[0093] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Add 1000 ppm of H2WO4 based on the W content and stir at 1200 rpm for 25 minutes in the high-speed mixer to mix evenly.

[0094] (4) The mixture obtained in step (3) is heated to 400°C at a heating rate of 2°C / min in an air atmosphere and sintered at this temperature for 5 hours. After sintering, the mixture is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for all-solid-state batteries.

[0095] ICP was used to detect the contents of Nb and W in the modified ternary cathode material prepared in this example. The Nb content (wt%) was X The W element content is 347ppm, Y 861ppm, wt X / S is 7.7×10 2 ppm m -2 g,wtY / S is 1.9×10 3 ppm m -2 g; The thickness of the outer coating layer d is 8nm, and the ratio of the thickness of the outer coating layer d to the specific surface area of ​​the modified ternary cathode material d / S is 18, and the ratio unit is nm m -2 The residual lithium content on the surface of the core ternary material matrix is ​​4235ppm, and after coating modification, the residual lithium content on the surface is 2105ppm.

[0096] Comparative Example 3:

[0097] The modified ternary cathode material used in the all-solid-state battery in this comparative example is a coated structure, which includes a core, an intermediate coating layer and an outer coating layer from the inside to the outside. The core is a ternary cathode material LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01 O2, the middle coating layer is a crystalline lithium-containing compound LiNbO3, the particle size of the middle coating layer is about 50nm, and the outer coating layer is an amorphous lithium-containing compound Li2WO4. The specific surface area S of the modified ternary positive electrode material is 0.55m 2 / g, and the electronic conductivity is 7.8×10 -7 S / cm.

[0098] The preparation method of the modified ternary cathode material for all-solid-state batteries of this comparative example comprises the following steps:

[0099] (1) Weigh 10 kg of ternary cathode material LiNi 0.85 Co 0.10 Mn 0.04 Al 0.01 O2 was added into a high-speed mixer, and 10,000 ppm of Nb2O5 was added based on the Nb content. The mixture was stirred at a speed of 800 rpm for 30 minutes in the high-speed mixer to mix evenly.

[0100] (2) The mixture obtained in step (1) was heated to 650°C at a heating rate of 5°C / min in an oxygen atmosphere and sintered for 12 hours. After sintering, the mixture was cooled, crushed, and sieved.

[0101] (3) Weigh 10 kg of the sintered material after screening in step (2) and add it to a high-speed mixer. Add 18,000 ppm of H2WO4 based on the W content and stir at 1,200 rpm in the high-speed mixer for 25 minutes to mix evenly.

[0102] (4) The mixture obtained in step (3) is heated to 400°C at a heating rate of 2°C / min in an oxygen atmosphere and sintered at this temperature for 5 hours. After sintering, the mixture is cooled, crushed, and sieved to obtain a modified ternary positive electrode material for all-solid-state batteries.

[0103] ICP was used to detect the contents of Nb and W in the modified ternary cathode material prepared in this example. The Nb content (wt%) was X 9524ppm, W element content wt Y 16897ppm, wt X / S is 1.7×10 4 ppm m -2 g,wt Y / S is 3.1×10 4 ppm m -2 g; The thickness of the outer coating layer d is 58nm, and the ratio of the thickness of the outer coating layer d to the specific surface area of ​​the modified ternary cathode material d / S is 105, and the unit of the ratio is nm m -2 The residual lithium content on the surface of the core ternary material matrix is ​​4235ppm, and the residual lithium content on the surface after coating modification is 1578ppm.

[0104] Assembly of all-solid-state mold batteries:

[0105] The steps for assembling the all-solid-state mold battery in a glove box protected by argon atmosphere are as follows:

[0106] 1) placing sulfide solid electrolyte Li6PS5Cl powder in a mold and applying pressure to press it into a tablet;

[0107] 2) The modified ternary cathode materials obtained in each example and comparative example were mixed with the solid electrolyte Li6PS5Cl and the conductive agent VGCF in a mass ratio of 70:29:1 to prepare a composite cathode. The composite cathode was then poured onto one side of the electrolyte sheet and pressed under pressure.

[0108] 3) Attach the indium sheet and lithium sheet to the other side of the electrolyte sheet in sequence, and then apply pressure;

[0109] 4) Assemble the mold battery.

[0110] Electrochemical test method:

[0111] The assembled all-solid-state mold battery was placed in a 30°C constant temperature chamber with a test voltage range of 2.1 to 3.7 V. The charge and discharge rates for the first three cycles were 0.1C, 0.2C, and 0.33C, respectively, followed by 50 charge and discharge cycles at a rate of 0.5C. The specific capacity at the first charge and discharge point, the first coulombic efficiency, and the capacity retention rate after 50 cycles of the examples and comparative examples are shown in Table 1.

[0112] Table 1 Electrochemical properties of modified ternary cathode materials in various examples and comparative examples

[0113] It can be seen from the data in Table 1 that the modified ternary cathode materials prepared in Examples 1-4 of the present application all exhibit excellent electrochemical properties in all-solid-state batteries. Compared with Comparative Examples 1-3, the first discharge specific capacity, first coulomb efficiency and 50-week cycle retention rate of the battery are all improved. The present application coats the surface of the ternary cathode material with an intermediate coating layer having ionic conductivity and an outer coating layer having ionic conductivity and electronic insulation, and controls the thickness of the outer coating layer by adjusting the coating amount of the outer coating layer according to the specific surface area of ​​the base material, thereby controlling the overall electronic conductivity of the modified ternary material within an appropriate range. Excessively high electronic conductivity cannot effectively inhibit interfacial side reactions, and excessively low electronic conductivity will hinder the progress of electrochemical reactions and affect material properties, while appropriate electronic conductivity can inhibit side reactions and space charge layers, and enhance the stability of the interface between the ternary cathode material and the sulfide solid electrolyte; in addition, the amorphous outer coating layer has good elasticity, and can also alleviate the strain caused by the expansion / contraction of the cathode material during the cycle, maintain good solid-solid interface contact, and enhance cycle stability.

[0114] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A modified ternary cathode material for all-solid-state batteries, wherein the modified ternary cathode material has a coated structure, and the coated structure sequentially includes a core, an island-shaped inner coating layer, and a layered outer coating layer from the inside to the outside; The core is a ternary cathode material matrix; The island-shaped inner coating layer is a crystalline Li a X b O c ,in, 0 < a ≤ 3, 0 < b ≤ 3, 0 < c ≤ 5, and the X element is selected from one or more of aluminum, titanium, vanadium, manganese, cobalt, yttrium, zirconium, niobium, lanthanum, cerium, tantalum, and tungsten; The layered outer coating is an amorphous Li α Y β O γ , wherein 0<α≤4, 0<β≤4, 0<γ≤7, and the Y element is selected from one or more of boron, silicon, phosphorus, sulfur, titanium, vanadium, antimony, molybdenum, and tungsten; The powder electronic conductivity of the modified ternary cathode material is 10 -4 -10 -2 S / cm.

2. The modified ternary cathode material according to claim 1, wherein: The chemical formula of the ternary cathode material matrix is LiNi x Co y Mn 1-x-y-z M z O2, where 0.50 ≤ x < 1.00, 0 < y ≤ 0.3, 0 < 1 - x - y - z ≤ 0.3, 0 < z ≤ 0.02, and M is selected from one or more of magnesium, aluminum, calcium, titanium, vanadium, strontium, yttrium, zirconium, niobium, molybdenum, barium, lanthanum, cerium, tantalum, and tungsten.

3. The modified ternary cathode material according to any one of claims 1 to 2, wherein: The crystalline Li a X b O c It is a lithium-containing compound with ion conductivity generated by the reaction of an oxygen-containing compound containing element X with residual lithium on the surface of a ternary positive electrode material.

4. The modified ternary cathode material according to any one of claims 1 to 3, wherein The specific surface area of ​​the modified ternary positive electrode material is 0.1-2m 2 / g.

5. The modified ternary cathode material according to claim 4, wherein: The particle size of the island-shaped inner coating layer is 10-500nm; the content of the X element in the island-shaped inner coating layer in the modified ternary positive electrode material is 100-30000ppm, and the ratio of the content of the X element in the island-shaped inner coating layer to the specific surface area of ​​the modified ternary positive electrode material is 10 3 -10 5 , the ratio unit is ppmm -2 g.

6. The modified ternary cathode material according to any one of claims 1 to 5, wherein: The amorphous Li α Y β O γ It is an amorphous lithium-containing compound with ionic conductivity and electronic insulation, which is generated by the reaction of an oxygen-containing compound containing the Y element with residual lithium on the surface of the ternary positive electrode material.

7. The modified ternary cathode material according to claim 4, wherein: The thickness of the layered outer coating layer is 1-30 nm, and the ratio of the thickness of the layered outer coating layer to the specific surface area of ​​the modified ternary positive electrode material is 1-100, and the ratio unit is nm m -2 g.

8. The modified ternary cathode material according to claim 4, wherein: The content of the Y element in the layered outer coating layer in the modified ternary positive electrode material is 100 to 10000 ppm, and the ratio of the content of the Y element to the specific surface area of ​​the modified ternary positive electrode material is 10 2 -10 4 , the ratio unit is ppm m -2 g.

9. A method for preparing a modified ternary cathode material according to any one of claims 1 to 8, comprising the following steps: (1) Mix the ternary cathode material matrix and the X-containing oxygen compound evenly; (2) Perform high-temperature sintering treatment on the mixture obtained in step (1), and after sintering is completed, cool, crush, and screen the sintered product; (3) Mix the sintered product screened in step (2) and the Y-containing oxygen compound evenly; (4) Perform low-temperature sintering treatment on the mixture obtained in step (3), and after sintering is completed, cool, crush, and screen the sintered product to obtain a modified ternary cathode material for all-solid-state batteries.

10. The preparation method according to claim 9, wherein In step (2), the high-temperature sintering temperature is 500 - 800 °C, the sintering time is 1 - 15 hours, and the high-temperature sintering is carried out in an oxygen or air atmosphere.

11. The preparation method according to any one of claims 9 to 10, wherein In step (4), the low-temperature sintering treatment temperature is 200 - 500 °C, the sintering time is 1 - 15 hours, and the low-temperature sintering is carried out in an oxygen or air atmosphere.

12. The preparation method according to any one of claims 9 to 11, wherein In steps (2) and (4), the mixing method is high-speed stirring, the rotation speed of the high-speed stirring is 100 - 2500 rpm, and the high-speed stirring time is 10 - 60 min.

13. An all-solid-state battery, wherein the cathode material used in the all-solid-state battery is the modified ternary cathode material according to any one of claims 1 to 8 or the modified ternary cathode material prepared by the preparation method according to any one of claims 9 to 12.

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