Positive electrode material for solid-state battery, preparation of positive electrode material and solid-state battery

Abstract

The invention provides a positive electrode material for a solid-state battery, preparation of the positive electrode material and the solid-state battery. The positive electrode material comprises a nickel-based layered positive electrode material core and a coating layer coating the surface of the nickel-based layered positive electrode material core; magnesium is doped in the nickel-based layered positive electrode material; and the coating layer comprises LiV3O8 and V2O5 (vanadium pentoxide). According to the invention, through the cooperation of the doping of magnesium and LiV3O8 and V2O5 in the coating layer, the mixed arrangement of Li < + > / Ni < 2 + > is reduced, the structural stability of the positive electrode material is improved, the rapid insertion of lithium ions is promoted, and the interface side reaction between the positive electrode and the solid-solid interface of the solid electrolyte layer is effectively inhibited; therefore, the interface stability, the rate capability and the cycle performance of the positive electrode material are enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and relates to a cathode material for solid-state batteries, its preparation, and solid-state batteries. Background Art

[0002] With the increasing global demand for sustainable development and clean energy, the widespread application of traditional lithium-ion batteries in fields such as electric vehicles, renewable energy storage, and portable electronic devices faces some challenges. Although lithium-ion batteries have high energy density and good cycle life, the flammability, leakage risk, and potential environmental hazards of their liquid electrolytes make safety issues increasingly prominent. In addition, the performance of lithium-ion batteries in high-temperature and low-temperature environments is also limited. To overcome these defects, solid-state batteries have emerged as an emerging technology.

[0003] Solid-state batteries use solid electrolytes, significantly improving safety, energy density, and cycle stability, making them an ideal choice to replace traditional lithium-ion batteries. In recent years, people have increasingly high requirements for the energy density, long cycle life, and safety of solid-state batteries. In this context, due to its special capabilities and cost-effectiveness, nickel-rich ternary cathode materials have become a promising competitor in the automotive industry. However, despite their potential, nickel-rich ternary cathode materials have many problems in the industrialization process, such as poor discharge performance, significant capacity deterioration under extreme temperature conditions, and when it comes to high temperatures, the material is prone to thermal runaway and many interfacial reactions, which lead to the reduction or dissolution of transition metal cations, the release of oxygen, and the anisotropic contraction of the layered structure, exacerbating the irreversible degradation of battery capacity. In addition, due to the similar diameters of Li + / Ni 2+ , the mixing of Li + / Ni 2+ results in the degradation of the ternary structure, causing phenomena such as lattice instability, cation disorder, phase change, and microcrack propagation, reducing the battery's cycle and rate performance.

[0004] Therefore, how to improve the structural stability of the cathode material for solid-state batteries and reduce the interfacial side reactions of the battery is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a cathode material for solid-state batteries, its preparation, and solid-state batteries. The present invention reduces the mixing of Li 3 O 8 and V 2 O 5 in the coating layer through the doping of magnesium and the synergistic cooperation of V + / Ni 2+The mixed arrangement enhances the structural stability of the cathode material, promotes the rapid insertion of lithium ions, and effectively inhibits the interfacial side reactions between the cathode and the solid-solid interface of the solid electrolyte layer, thereby enhancing the interfacial stability, rate performance, and cycling performance of the cathode material.

[0006] To achieve the object of the present invention, the following technical solutions are adopted:

[0007] In a first aspect, the present invention provides a cathode material for a solid-state battery, the cathode material comprising a nickel-based layered cathode material core and a coating layer coated on the surface of the nickel-based layered cathode material core; magnesium is doped in the nickel-based layered cathode material; the coating layer comprises LiV 3 O 8 and V 2 O 5 .

[0008] In the present invention, Mg element is incorporated into the nickel-based layered cathode material. Mg 2+ will replace Li + and Ni 2+ with similar ionic radii, and can occupy the transition metal sites and / or lithium sites, which is beneficial to the rapid migration of lithium ions, reduces the mixing arrangement of Li + / Ni 2+ , and improves the rate performance of the material; in addition, the bulk doping of Mg element also forms strong Mg-O bonds, improves the stability of the internal crystal structure of the material, can effectively stabilize the layered structure of the material, and promotes the rapid insertion of lithium ions; further, in cooperation with LiV 3 O 8 and V 2 O 5 in the coating layer, it improves the transport ability of Li ions at the interface, slows down the release of surface oxygen and the anisotropic shrinkage of the layered structure, and at the same time inhibits the interfacial reactive oxygen species and the solid-solid contact between the cathode of the solid-state battery and the electrolyte layer interface, effectively inhibits the interfacial side reactions, thereby enhancing the interfacial stability of the cathode material and improving the cycling performance.

[0009] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0010] Preferably, the chemical general formula of the nickel-based layered cathode material is LiNi x Mg y M z O 2, where x ≥ 0.6, 0.02 ≤ y ≤ 0.1, z > 0, and x + y + z = 1. M includes transition metal elements, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0011] For example, x can be 0.6, 0.63, 0.65, 0.68, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, 0.83, 0.85, 0.88, 0.9, 0.93, or 0.95, etc.; y can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, etc.; z can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, or 0.35, etc. However, it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0012] The nickel-based layered cathode material provided by the present invention is selected from nickel-rich cathode materials LiNi x Mg y M z O 2 , which is more conducive to its application in solid-state batteries. Further, the stoichiometric ratio of magnesium is regulated to 0.02 ≤ y ≤ 0.1, which is more conducive to determining the doping amount of Mg in the ternary precursor with optimal electrochemical performance; it not only stabilizes the crystal structure inside the material but also prevents Mg from occupying too many transition metal sites, resulting in loss of battery capacity. On the other hand, it can reduce the cost of the material to a certain extent and promote the marketization of material preparation.

[0013] Preferably, M includes any one or a combination of at least two of Co, Mn, or Al.

[0014] The nickel-based layered cathode material provided by the present invention, in addition to nickel and the doped magnesium element, may also include other conventional transition metal elements for lithium-ion layered cathode materials. Those skilled in the art can make adaptive selection and adjustment according to actual needs.

[0015] In a second aspect, the present invention provides a method for preparing a cathode material for a solid-state battery as described in the first aspect. The preparation method includes the following steps:

[0016] A nickel-magnesium mixed salt solution, a precipitant solution, and a complexing agent solution are added in parallel flow to carry out a coprecipitation reaction to obtain a magnesium-doped precursor material;

[0017] The magnesium-doped precursor material is mixed with a lithium source and sintered to obtain a sintered product;

[0018] Mix the sintered product with vanadate for coating and perform heat treatment to obtain the cathode material for the solid-state battery.

[0019] In the preparation method provided by the present invention, bulk doping of magnesium is achieved in the precursor preparation stage, better exerting the doping effect of magnesium. After subsequent lithium doping and sintering, there is no need for water washing after sintering, and directly perform coating treatment with vanadate. Under the action of heat treatment, LiV 3 O 8 and V 2 O 5 can be obtained simultaneously. A composite coating layer is prepared, and a cathode material with excellent performance and more suitable for solid-state batteries is obtained; in addition, the preparation method of the present invention also has the advantages of easy control of preparation conditions, high reproducibility, and can obtain materials with uniform chemical composition and uniform particle size distribution; the synthesis process is simple, the operation is convenient, the requirements for equipment are low, and there is no generation of solid-liquid waste, which is suitable for large-scale production.

[0020] In the present invention, after lithium doping and sintering, there is no need for water washing, and directly perform coating with vanadate. Vanadate can react with the residual alkali on the surface of the sintered product, and under the action of heat treatment, LiV 3 O 8 and V 2 O 5 are obtained simultaneously.

[0021] Preferably, the nickel-magnesium mixed salt solution further includes an M salt, and the M element in the M salt includes a transition metal element.

[0022] Preferably, the pH value of the coprecipitation reaction is 10.5 - 11.5, such as 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4 or 11.5, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0023] Preferably, the rotation speed of the coprecipitation reaction is 400 - 550 rpm, such as 400 rpm, 430 rpm, 450 rpm, 480 rpm, 500 rpm, 530 rpm or 550 rpm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0024] Preferably, the temperature of the coprecipitation reaction is 50 - 60 °C, such as 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0025] Preferably, wash and dry the material after the coprecipitation reaction.

[0026] Preferably, the median particle size D50 of the magnesium-doped precursor material is 2.5 to 3.5 μm, such as 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm or 3.5 μm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0027] It should be noted that except for the above-mentioned characteristic limitations on the coprecipitation reaction, the selection of other raw materials, the concentration range, and the flow control are all conventional technical solutions. The coprecipitation methods for preparing the cathode precursor material are all applicable to the present invention, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0028] For example, the salts in the nickel-magnesium mixed salt solution include but are not limited to at least one of sulfates, nitrates, acetates or chlorides; the precipitants include but are not limited to sodium hydroxide, potassium hydroxide, sodium carbonate or carbonic acid; the complexing agents include but are not limited to at least one of ammonia water, ammonium bicarbonate, ammonium phosphate, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium nitrate, urea or citric acid.

[0029] Preferably, the sintering atmosphere includes an oxygen-containing atmosphere.

[0030] The oxygen-containing atmosphere in the present invention is a reaction atmosphere containing oxygen. For example, it can be a pure oxygen atmosphere, an air atmosphere, or a mixed gas atmosphere of oxygen and a gas that does not affect the reaction.

[0031] Preferably, the sintering includes first sintering and second sintering in sequence.

[0032] Preferably, the heating rate of the first sintering is 3 to 5 °C / min, such as 3 °C / min, 4 °C / min or 5 °C / min, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0033] Preferably, the temperature of the first sintering is 450 to 550 °C, such as 450 °C, 460 °C, 470 °C, 480 °C, 490 °C, 500 °C, 510 °C, 520 °C, 530 °C, 540 °C or 550 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0034] Preferably, the time of the first sintering is 5 to 7 h, such as 5 h, 6 h or 7 h, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0035] Preferably, the heating rate of the second sintering is 2 - 3 °C / min, such as 2 °C / min or 3 °C / min, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0036] Preferably, the temperature of the second sintering is 700 - 800 °C, such as 700 °C, 710 °C, 720 °C, 730 °C, 740 °C, 750 °C, 760 °C, 770 °C, 780 °C, 790 °C or 800 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0037] Preferably, the time of the second sintering is 10 - 15 h, such as 10 h, 11 h, 12 h, 13 h, 14 h or 15 h, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0038] Preferably, the vanadate includes ammonium vanadate.

[0039] In the present invention, ammonium vanadate is selected as the coating material, which is more conducive to the reaction with the surface residual alkali and the decomposition of the product during the subsequent heat treatment process, thereby obtaining a coating layer structure in which LiV 3 O 8 and V 2 O 5 exist simultaneously.

[0040] Preferably, the mass ratio of the vanadate to the sintered product is (1 - 7):100, such as 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100, 5.5:100, 6:100, 6.5:100 or 7:100, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0041] In the present invention, the mass ratio of the vanadate to the sintered product being (1 - 7):100 is more conducive to preparing a LiV 3 O 8 and V 2 O 5 coating layer with a suitable thickness; while being able to inhibit the interfacial side reactions between the positive electrode and the solid - solid interface of the solid electrolyte layer, and prevent the rate performance of the battery from deteriorating due to the inability of the too - thick coating layer to provide a channel for the migration of lithium ions.

[0042] Preferably, the temperature of the heat treatment is 150 to 350 °C, such as 150 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C or 350 °C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] In the present invention, by controlling the temperature of the heat treatment to be 150 to 350 °C, a coating layer structure of a mixed material of LiV 3 O 8 and V 2 O 5 can be simultaneously decomposed. However, if the temperature is too low or too high, the decomposition effect will be affected, resulting in a serious reduction in the coating effect.

[0044] Preferably, the time of the heat treatment is 5 to 8 h, such as 5 h, 6 h, 7 h or 8 h, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0045] As a preferred technical solution, the preparation method includes the following steps:

[0046] The nickel-magnesium mixed salt solution, the precipitant solution and the complexing agent solution are added in parallel flow, maintaining the pH value at 10.5 to 11.5, and a coprecipitation reaction is carried out at 50 to 60 °C at a rotation speed of 400 to 550 rpm, followed by washing and drying to obtain a magnesium-doped precursor material;

[0047] The magnesium-doped precursor material is mixed with a lithium source. Under an oxygen-containing atmosphere, it is first heated to 450 to 550 °C at a rate of 3 to 5 °C / min for the first sintering for 5 to 7 h, and then heated to 700 to 800 °C at a rate of 2 to 3 °C / min for the second sintering for 10 to 15 h to obtain a sintered product;

[0048] The sintered product is mixed and coated with ammonium vanadate, and heat-treated at 150 to 350 °C for 5 to 8 h to obtain the positive electrode material for the solid-state battery.

[0049] It should also be noted that when performing the lithium-doping sintering of the magnesium-doped precursor material in the present invention, the selected lithium source and the specific addition amount are both conventional technical solutions.

[0050] For example, the lithium source includes but is not limited to at least one of lithium hydroxide, lithium nitrate, lithium carbonate or lithium acetate; the molar ratio of lithium in the lithium source to the total molar amount of all metal elements in the magnesium-doped precursor material is (1 to 1.05):1 (such as 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1, etc.), that is, lithium can be added in excess to a certain extent.

[0051] In addition, the method of mixed coating in the present invention is not particularly limited, and any method that can achieve the coating of vanadate on the surface of the sintered product is applicable to the present invention. For example, solid-phase mixing coating can be directly carried out, or liquid-phase coating can be carried out. When liquid-phase coating is carried out, ethanol is used as the solvent.

[0052] In a third aspect, the present invention also provides a solid-state battery, which includes the positive electrode material as described in the first aspect or the positive electrode material prepared by the preparation method as described in the second aspect.

[0053] The solid-state battery in the present invention includes a positive electrode sheet containing the positive electrode material provided by the present invention, a solid electrolyte layer, and a negative electrode sheet. Except for the positive electrode material of the present invention, the types of the remaining raw materials and the preparation process are all conventional technical solutions, and the materials and preparation processes that can be used in solid-state batteries in the prior art are all applicable to the present invention.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) In the present invention, Mg element is incorporated into the nickel-based layered positive electrode material. Mg 2+ will replace Li + and Ni 2+ with similar ionic radii, and can occupy the transition metal sites and / or lithium sites, which is beneficial to the rapid migration of lithium ions, reduces the mixing of Li + / Ni 2+ , and improves the rate performance of the material. In addition, the bulk doping of Mg element also forms strong Mg-O bonds, improves the stability of the internal crystal structure of the material, can effectively stabilize the layered structure of the material, and promotes the rapid insertion of lithium ions. Further, the LiV 3 O 8 and V 2 O 5 of the synergistic coating layer are coordinated to improve the transport ability of Li ions at the interface, slow down the release of surface oxygen and the anisotropic shrinkage of the layered structure, and at the same time inhibit the interfacial reactive oxygen species and the solid-solid contact between the positive electrode and the electrolyte layer interface of the solid-state battery, effectively inhibiting the interfacial side reactions, thereby enhancing the interfacial stability of the positive electrode material and improving the cycle performance.

[0056] (2) The preparation method provided by the present invention realizes the bulk doping of magnesium in the precursor preparation stage, better exerts the doping effect of magnesium. After subsequent lithium matching sintering, there is no need to wash with water after sintering, and it is directly coated with vanadate. Under the action of heat treatment, LiV 3 O 8 and V 2 O 5The composite coating layer was used to prepare a cathode material with excellent performance and more suitable for solid-state batteries. In addition, the preparation method of the present invention also has the advantages of easy control of preparation conditions, high reproducibility, and can obtain materials with uniform chemical composition and particle size distribution. The synthesis process is simple, the operation is convenient, the requirements for equipment are low, and there is no generation of solid-liquid waste, which is suitable for large-scale production. Detailed Embodiments

[0057] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0059] In the description of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality" means two or more unless otherwise specifically defined.

[0060] Example 1

[0061] This example provides a cathode material for a solid-state battery, and the cathode material includes a nickel-based layered cathode material core and a coating layer coated on the surface of the nickel-based layered cathode material core.

[0062] The chemical formula of the nickel-based layered cathode material is LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 ; the coating layer includes LiV 3 O 8 and V 2 O 5 .

[0063] The preparation method of the cathode material is as follows:

[0064] S1: Prepare NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO according to the molar ratio of Mn:Mg:Co:Mn = 0.75:0.05:0.1:0.14 ·H 2 O and Mg(NO 3 ) 2 mixed aqueous solution, select a NaOH solution with a mass fraction of 40% as the precipitant solution and an ammonia water with a mass fraction of 22% as the complexing agent solution;

[0065] Add a bottom liquid with a pH value of 10.3 - 10.5 to the reaction kettle. The bottom liquid consists of pure water, sodium hydroxide, and ammonia water. Add the mixed aqueous solution, precipitant solution, and complexing agent solution into the reaction kettle in parallel. The feed flow rate of the mixed aqueous solution is 50 L / h, and carry out a coprecipitation reaction. Throughout the reaction, introduce N 2 to prevent oxidation. The reaction conditions are: pH value is 10.5 - 10.8, temperature is 60 °C, rotation speed is 500 rpm. After the coprecipitation reaction is completed, successively use a NaOH solution with a mass fraction of 4% and an aqueous solution to centrifuge and wash the obtained solution, and then dry it to obtain a magnesium-doped precursor material Ni 0.75 Mg 0.05 Co 0.1 Mn 0.1 (OH) 2 ;

[0066] S2: Mix the magnesium-doped precursor material Ni 0.75 Mg 0.05 Co 0.1 Mn 0.1 (OH) 2 and LiOH·H 2 O powder in a molar ratio of 1:1.05. Raise the temperature to 500 °C at a heating rate of 5 °C / min in an oxygen atmosphere for the first sintering, keep it warm for 5 h, then raise the temperature to 780 °C at a heating rate of 3 °C / min for the second sintering, keep it warm for 15 h, and cool it to room temperature to obtain a sintered product LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 powder;

[0067] S3: Dissolve ammonium vanadate (NH 4 VO 3 ) in absolute ethanol heated to 85 °C, and at the same time add the sintered product LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 powder, where NH 4 VO 3 and LiNi 0.75 Mg 0.05 Co 0.1 Mn0.1 O 2 The mass ratio of is 2.5:100, and after stirring and dispersing evenly, the obtained suspension is slowly evaporated with ethanol while continuously stirring for 4 h, and then heat-treated at 250 °C for 5 h to obtain the positive electrode material.

[0068] Example 2

[0069] This example provides a positive electrode material for a solid-state battery, and the positive electrode material includes a nickel-based layered positive electrode material core and a coating layer coated on the surface of the nickel-based layered positive electrode material core

[0070] The chemical formula of the nickel-based layered positive electrode material is LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 ; the coating layer includes LiV 3 O 8 and V 2 O 5 .

[0071] The preparation method of the positive electrode material is as follows:

[0072] S1: Prepare a mixed aqueous solution of NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO 4 ·H 2 O and Mg(NO 3 ) 2 according to the molar ratio of Mn:Mg:Co:Mn = 0.75:0.05:0.1:0.1, and select a NaOH solution with a mass fraction of 40% as the precipitating agent solution and an ammonia water with a mass fraction of 22% as the complexing agent solution;

[0073] Add a bottom liquid with a pH value of 10.5 - 10.8 to the reaction kettle. The bottom liquid is composed of pure water, sodium hydroxide and ammonia water. Add the mixed aqueous solution, the precipitating agent solution and the complexing agent solution into the reaction kettle in parallel. The feeding flow rate of the mixed aqueous solution is 50 L / h, and carry out a coprecipitation reaction. N 2 is introduced throughout the reaction to prevent oxidation. The reaction conditions are: pH value is 10.8 - 11, temperature is 60 °C, rotation speed is 550 rpm. After the coprecipitation reaction is completed, the obtained solution is centrifugally washed and dried successively with a NaOH solution with a mass fraction of 4% and an aqueous solution to obtain a magnesium-doped precursor material Ni 0.75 Mg 0.05 Co 0.1 Mn 0.1 (OH) 2;

[0074] S2: Mix the magnesium-doped precursor material Ni 0.75 Mg 0.05 Co 0.1 Mn 0.1 (OH) 2 and LiOH·H 2 O powders in a molar ratio of 1:1.05, heat them to 480 °C at a heating rate of 3 °C / min in an oxygen atmosphere for the first sintering, keep the temperature for 7 h, then heat them to 700 °C at a heating rate of 2 °C / min for the second sintering, keep the temperature for 15 h, and cool to room temperature to obtain the sintered product LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 powder;

[0075] S3: Dissolve ammonium vanadate (NH 4 VO 3 ) in anhydrous ethanol heated to 85 °C, and at the same time add the sintered product LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 powder, where the mass ratio of NH 4 VO 3 to LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 is 1.5:100, stir and disperse evenly, slowly evaporate the obtained suspension with ethanol while continuously stirring for 4 h, and then heat-treat at 350 °C for 8 h to obtain the positive electrode material.

[0076] Example 3

[0077] This example provides a positive electrode material for a solid-state battery, and the positive electrode material includes a nickel-based layered positive electrode material core and a coating layer coated on the surface of the nickel-based layered positive electrode material core

[0078] The chemical formula of the nickel-based layered positive electrode material is LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 ; The coating layer includes LiV 3 O 8 and V 2 O 5 .

[0079] The preparation method of the positive electrode material is as follows:

[0080] S1: Prepare an aqueous mixed solution of NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO 4 ·H 2 O and Mg(NO 3 ) 2 at a molar ratio of Mn:Mg:Co:Mn = 0.75:0.05:0.1:0.1. Select a NaOH solution with a mass fraction of 40% as the precipitant solution and an ammonia water solution with a mass fraction of 22% as the complexing agent solution;

[0081] Add a bottom liquid with a pH value of 10.3 - 10.5 to the reaction kettle. The bottom liquid is composed of pure water, sodium hydroxide, and ammonia water. Add the aqueous mixed solution, the precipitant solution, and the complexing agent solution into the reaction kettle in a co-current manner. The feeding flow rate of the aqueous mixed solution is 50 L / h, and carry out a co-precipitation reaction. Pass N 2 throughout the reaction to prevent oxidation. The reaction conditions are: pH value is 10.5 - 10.8, temperature is 50 °C, rotation speed is 400 rpm. After the co-precipitation reaction is completed, successively use a NaOH solution with a mass fraction of 4% and an aqueous solution to centrifugally wash the obtained solution, and then dry it to obtain a magnesium-doped precursor material Ni 0.75 Mg 0.05 Co 0.1 Mn 0.1 (OH) 2 with a D50 of 3 μm;

[0082] S2: Mix the magnesium-doped precursor material Ni 0.75 Mg 0.05 Co 0.1 Mn 0.1 (OH) 2 and LiOH·H 2 O powder at a molar ratio of 1:1.05. Under an oxygen atmosphere, raise the temperature to 550 °C at a heating rate of 4 °C / min for the first sintering, hold for 6 h, then raise the temperature to 800 °C at a heating rate of 3 °C / min for the second sintering, hold for 10 h, and cool to room temperature to obtain a sintered product LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 powder;

[0083] S3: Dissolve ammonium vanadate (NH 4 VO 3 ) in absolute ethanol heated to 85 °C, and at the same time add the sintered product LiNi 0.75 Mg0.05 Co 0.1 Mn 0.1 O 2 Powder, in which NH 4 VO 3 and LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 The mass ratio is 7.5:100. Stir and disperse evenly. The obtained suspension is slowly evaporated with ethanol while continuously stirring for 4 h, and then heat-treated at 150 °C for 5 h to obtain the positive electrode material.

[0084] Example 4

[0085] The difference between this example and Example 1 is that in this example, the chemical formula of the nickel-based layered positive electrode material is LiNi 0.7 Mg 0.1 Co 0.1 Mn 0.1 O 2 .

[0086] In step S1 of the preparation method, prepare a mixed aqueous solution of NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO 4 ·H 2 O and Mg(NO 3 ) 2 in a molar ratio of Mn:Mg:Co:Mn = 0.7:0.1:0.1:0.1; obtain Ni 0.7 Mg 0.1 Co 0.1 Mn 0.1 (OH) 2 .

[0087] The remaining preparation methods and parameters are the same as those in Example 1.

[0088] Example 5

[0089] The difference between this example and Example 1 is that in this example, the chemical formula of the nickel-based layered positive electrode material is LiNi 0.78 Mg 0.02 Co 0.1 Mn 0.1 O 2 .

[0090] In step S1 of the preparation method, prepare a mixed aqueous solution of NiSO 4 ·6H2 O, CoSO 4 ·7H 2 O, MnSO 4 ·H 2 O and Mg(NO 3 ) 2 mixed aqueous solution; obtaining Ni 0.78 Mg 0.02 Co 0.1 Mn 0.1 (OH) 2 .

[0091] The remaining preparation methods and parameters are the same as those in Example 1.

[0092] Example 6

[0093] The difference between this example and Example 1 is that in this example, the chemical formula of the nickel-based layered cathode material is LiNi 0.65 Mg 0.15 Co 0.1 Mn 0.1 O 2 .

[0094] In step S1 of the preparation method, NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O, MnSO 4 ·H 2 O and Mg(NO 3 ) 2 are prepared into a mixed aqueous solution according to the molar ratio of Mn:Mg:Co:Mn = 0.65:0.15:0.1:0.1; obtaining Ni 0.65 Mg 0.15 Co 0.1 Mn 0.1 (OH) 2 .

[0095] The remaining preparation methods and parameters are the same as those in Example 1.

[0096] Example 7

[0097] The difference between this example and Example 1 is that in step S3 of the preparation method of this example, the mass ratio of NH 4 VO 3 to LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 is 0.5:100.

[0098] The remaining preparation methods and parameters are the same as those in Example 1.

[0099] Example 8

[0100] The difference between this example and Example 1 is that in step S3 of the preparation method of this example, the mass ratio of NH 4 VO 3 to LiNi 0.75 Mg 0.05 Co 0.1 Mn 0.1 O 2 is 8:100.

[0101] The remaining preparation methods and parameters are the same as those in Example 1.

[0102] Example 9

[0103] The difference between this example and Example 1 is that in step S3 of the preparation method of this example, the heat treatment temperature is 100 °C.

[0104] The remaining preparation methods and parameters are the same as those in Example 1.

[0105] Example 10

[0106] The difference between this example and Example 1 is that in step S3 of the preparation method of this example, the heat treatment temperature is 400 °C.

[0107] The remaining preparation methods and parameters are the same as those in Example 1.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that in the positive electrode material of this comparative example, the chemical formula of the nickel-based layered positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , that is, the material in the core is not doped with magnesium.

[0110] In step S1 of the preparation method, an aqueous solution of NiSO 4 ·6H 2 O, CoSO 4 ·7H 2 O and MnSO 4 ·H 2 O is prepared according to the molar ratio of Mn:Co:Mn = 0.8:0.1:0.1.

[0111] The remaining preparation methods and parameters are the same as those in Example 1.

[0112] Comparative Example 2

[0113] The difference between this comparative example and Example 1 is that the positive electrode material in this comparative example does not contain a coating layer.

[0114] In the preparation method, step S3 is not carried out.

[0115] The remaining preparation methods and parameters are the same as those in Example 1.

[0116] Comparative Example 3

[0117] The difference between this comparative example and Example 1 is that the coating layer of the positive electrode material in this comparative example only contains V 2 O 5 .

[0118] In the preparation method, V 2 O 5 is used to replace the original coating NH 4 VO 3 .

[0119] The remaining preparation methods and parameters are the same as those in Example 1.

[0120] [Preparation and Performance Testing of Solid-State Lithium-Ion Batteries]

[0121] I) Preparation of Solid-State Lithium-Ion Batteries:

[0122] Positive electrode sheet: The positive electrode materials, conductive carbon black, and solid electrolyte Li 6 PS 5 Cl provided in Examples 1-10 and Comparative Examples 1-3 were dissolved in N,N-dimethylformamide (DMF) at a mass ratio of 69:30:1 and stirred evenly to obtain a positive electrode active paste. The positive electrode active paste was coated on the surface of an aluminum foil current collector, dried and roll-pressed to obtain a positive electrode sheet.

[0123] Negative electrode sheet: Artificial graphite, styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a mass ratio of 92:3:5 and stirred evenly to obtain a negative electrode active paste. The negative electrode active paste was coated on a copper foil current collector and dried and roll-pressed to obtain a negative electrode sheet.

[0124] Solid electrolyte layer: Li 6 PS 5 Cl layer.

[0125] The positive electrode sheet, solid electrolyte layer, and negative electrode sheet were assembled by a lamination process under Ar atmosphere at a pressure of 6.8 MPa to fabricate a soft-pack solid-state lithium-ion battery.

[0126] II) Performance Testing of Solid-State Lithium-Ion Batteries:

[0127] (a) Specific capacity: Constant current charge-discharge test: The assembled button cell is clamped on a Blue Power charge-discharge instrument for constant current charge-discharge test. The charge-discharge voltage is 2.5 - 3.7 V, and the current density is 0.5 C. The specific capacities of the first charge and discharge of the solid-state battery assembled with the prepared ternary material are measured respectively.

[0128] (b) Rate performance: The battery is charged at a constant current and constant voltage of 0.2 - 1.2 C to 3.7 V, and then discharged to 2.5 V at the same current density. The maximum discharge or charge rate is obtained when the battery does not fail (the determination condition for failure is that the cycle performance decays by more than 20%).

[0129] (c) Cycle performance: At a current density of 0.5 C, the charge-discharge cut-off voltages are set to 3.7 V / 2.5 V, and the battery is cycled for charge and discharge. The capacity retention rate after 100 cycles is measured.

[0130] The test results of the above tests are shown in Table 1.

[0131] Table 1

[0132]

[0133] In summary, in the present invention, Mg element is incorporated into the nickel-based layered cathode material. Mg 2+ will replace Li + and Ni 2+ with similar ionic radii, and can occupy the transition metal sites and / or lithium sites, which is beneficial to the rapid migration of lithium ions, reduce the mixing of Li + / Ni 2+ , and improve the rate performance of the material; in addition, the bulk doping of Mg element also forms strong Mg-O bonds, improves the stability of the internal crystal structure of the material, can effectively stabilize the layered structure of the material, and promote the rapid insertion of lithium ions; further, the synergistic coating of LiV 3 O 8 and V 2 O 5 improves the transport ability of Li ions at the interface, slows down the release of surface oxygen and the anisotropic shrinkage of the layered structure, and at the same time inhibits the interfacial reactive oxygen species and the solid-solid contact between the solid-state battery cathode and the electrolyte layer interface, effectively inhibits the interfacial side reactions, thereby enhancing the interfacial stability of the cathode material and improving the cycle performance.

[0134] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A positive electrode material for a solid-state battery, characterized in that: The positive electrode material comprises a nickel-based layered positive electrode material core and a coating layer coated on the surface of the nickel-based layered positive electrode material core; magnesium is doped in the nickel-based layered positive electrode material; and the coating layer comprises LiV3O8 and V2O5.

2. The positive electrode material for solid-state batteries according to claim 1, characterized in that: The general chemical formula of the nickel-based positive electrode material is LiNi x Mg y M z O2, wherein x≥0.6, 0.02≤y≤0.1, z>0, x+y+z=1, and M includes transition metal elements; Preferably, the M includes any one of Co, Mn or Al, or a combination of at least two of them.

3. A method for preparing a positive electrode material for a solid-state battery as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: Adding a nickel-magnesium mixed salt solution, a precipitant solution and a complexing agent solution in parallel to perform a coprecipitation reaction to obtain a magnesium-doped precursor material; Mixing a magnesium-doped precursor material with a lithium source and sintering to obtain a sintered product; The sintered product is mixed and coated with vanadate, and subjected to heat treatment to obtain the positive electrode material for the solid-state battery.

4. The preparation method according to claim 3, characterized in that: The nickel-magnesium mixed salt solution also includes M salt, and the M element in the M salt includes a transition metal element; Preferably, the pH value of the coprecipitation reaction is 10.5 to 11.5; Preferably, the rotation speed of the coprecipitation reaction is 400-550 rpm, and the temperature of the coprecipitation reaction is 50-60° C.; Preferably, the material after the coprecipitation reaction is washed and dried; Preferably, the median particle size D50 of the magnesium-doped precursor material is 2.5-3.5 μm.

5. The preparation method according to claim 3 or 4, characterized in that: The sintering atmosphere includes an oxygen-containing atmosphere; Preferably, the sintering includes performing a first sintering and a second sintering in sequence.

6. The preparation method according to claim 5, characterized in that: The heating rate of the first sintering is 3-5°C / min, the temperature of the first sintering is 450-550°C, and the time of the first sintering is 5-7h; Preferably, the heating rate of the second sintering is 2-3° C. / min, the temperature of the second sintering is 700-800° C., and the time of the second sintering is 10-15 h.

7. The preparation method according to claim 3, characterized in that: The vanadate includes ammonium vanadate; Preferably, the mass ratio of the vanadate to the sintered product is (1-7):

100.

8. The preparation method according to claim 3 or 7, characterized in that: The temperature of the heat treatment is 150-350° C., and the time of the heat treatment is 5-8 hours.

9. The preparation method according to claim 3, characterized in that: The preparation method comprises the following steps: Adding a nickel-magnesium mixed salt solution, a precipitant solution and a complexing agent solution in parallel, maintaining a pH value of 10.5 to 11.5, performing a coprecipitation reaction at 50 to 60° C. at a rotation speed of 400 to 550 rpm, washing, and drying to obtain a magnesium-doped precursor material; The magnesium-doped precursor material is mixed with a lithium source, and in an oxygen-containing atmosphere, the temperature is first raised to 450-550° C. at 3-5° C. / min for a first sintering for 5-7 hours, and then the temperature is raised to 700-800° C. at 2-3° C. / min for a second sintering for 10-15 hours to obtain a sintered product; The sintered product is mixed and coated with ammonium vanadate, and heat treated at 150 to 350° C. for 5 to 8 hours to obtain the positive electrode material for the solid-state battery.

10. A solid-state battery, characterized in that: The solid-state battery comprises the positive electrode material as described in claim 1 or 2 or the positive electrode material prepared by the preparation method as described in any one of claims 3-9.

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