An ultrahigh-nickel single-crystal positive electrode material, a preparation method and a positive electrode

Abstract

This invention relates to an ultra-high nickel single-crystal cathode material, its preparation method, and the cathode itself. The preparation method includes the following steps: preparing a nickel-cobalt precursor and carbon-doped nano-manganese oxide; mixing a lithium source, the nickel-cobalt precursor, and the carbon-doped nano-manganese oxide, and performing a first heat treatment in an oxygen-containing atmosphere to obtain a sintered material; mixing the sintered material with the carbon-doped nano-manganese oxide, and performing a second heat treatment in a protective atmosphere to obtain the ultra-high nickel single-crystal cathode material. This invention first prepares a nickel-cobalt precursor, and then adds carbon-doped nano-manganese oxide in stages during the first and second heat treatments. This optimizes the process difficulty in preparing the single-crystal precursor, thereby reducing the sintering temperature and preventing excessive lithium-nickel mixing due to high temperatures. Simultaneously, during the second heat treatment, carbon is directly coated while manganese is being coated, improving the rate performance of the ultra-high nickel single-crystal cathode material.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a cathode material, particularly to an ultra-high nickel single crystal cathode material, its preparation method, and the cathode itself. Background Technology

[0002] Solid-state batteries have powerful advantages such as high safety, high energy density, long cycle life and wide operating temperature. They are not only the future of electric vehicles, but can also bring revolutionary changes to many fields such as aviation and energy storage.

[0003] However, solid-state batteries face serious solid-solid interface problems. Traditional polycrystalline NCM materials are prone to particle breakage and interface degradation during cycling. Single-crystal NCM, due to its intact structure, high mechanical strength, and excellent cycle stability, is the most promising material for solving the interface problem of solid-state batteries. To ensure that single-crystal cathode materials have good electrochemical performance in solid-state batteries, the material needs to have a small particle size and be a plate-like material dominated by the (001) plane. This requires the precursor to have a small particle size and better crystallinity, with primary particles exhibiting a coarse plate-like shape. Since the manganese element in the ternary precursor is very sensitive to oxygen, the reaction of the precursor needs to be controlled in an inert gas atmosphere, and the reaction equipment needs to have good airtightness. As long as the precursor is oxidized, the primary particles of the precursor will become finer. Fluctuations in the gas atmosphere during the reaction will also lead to uneven precursor structure, ultimately resulting in uneven cathode material structure. However, in the process of mass production of precursors, it is difficult to ensure that there is no slight oxidation during the preparation process, so the reproducibility of such precursors in large-scale production is not high.

[0004] Therefore, it is necessary to provide an ultra-high nickel single crystal cathode material, its preparation method, and the cathode itself. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an ultra-high nickel single-crystal cathode material, its preparation method, and the cathode itself. The preparation method first prepares a nickel-cobalt precursor, and then adds carbon-doped nano-manganese oxide in steps during the first and second heat treatment stages, thereby optimizing the process difficulty in the preparation of the single-crystal precursor. At the same time, carbon is directly coated while manganese is coated during the second heat treatment, which improves the rate performance of the ultra-high nickel single-crystal cathode material.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing an ultra-high nickel single-crystal cathode material, the method comprising the following steps:

[0008] (1) Preparation of nickel-cobalt precursor and carbon-doped nano-manganese oxide;

[0009] (2) A mixture of lithium source, nickel-cobalt precursor and carbon-doped nano-manganese oxide is subjected to a first heat treatment in an oxygen-containing atmosphere to obtain a sintered material;

[0010] (3) Mix the calcined material with carbon-doped nano-manganese oxide and perform a second heat treatment in a protective atmosphere to obtain the ultra-high nickel single crystal cathode material.

[0011] Nickel and cobalt have similar properties. The preparation method provided by this invention first prepares a nickel-cobalt precursor, providing industrial feasibility of the process. Then, carbon-doped nano-manganese oxide is added stepwise in the first and second heat treatment stages, which optimizes the process difficulty in the preparation of the single crystal precursor, thereby reducing the sintering temperature and preventing excessive temperature from causing severe lithium-nickel mixing in the material. At the same time, carbon is directly coated while coating manganese in the second heat treatment, replacing some of the carbon black added in the electrode preparation process, thus improving the rate performance of the ultra-high nickel single crystal cathode material.

[0012] In the preparation method provided by this invention, the carbon-doped nano-manganese oxide in step (2) and the carbon-doped nano-manganese oxide in step (3) can be all of the carbon-doped nano-manganese oxide prepared in step (1); or they can be some of the carbon-doped nano-manganese oxide prepared in step (1). As long as the carbon-doped nano-manganese oxide that meets the process requirements can be provided for steps (2) and (3).

[0013] In some embodiments, the method for preparing the nickel-cobalt precursor includes a co-precipitation method.

[0014] In some embodiments, the coprecipitation method includes the following steps: co-flow mixing of a nickel-cobalt salt solution, a precipitant solution, and a complexing agent solution, followed by a coprecipitation reaction to obtain the nickel-cobalt precursor.

[0015] In some embodiments, the pH value of the coprecipitation reaction is 9 to 12, for example, it can be 9, 10, 11 or 12, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] In some embodiments, the temperature of the coprecipitation reaction is 20°C to 80°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] In some embodiments, during the coprecipitation reaction, the concentration of the complexing agent in the system is 1 g / L to 10 g / L, for example, it can be 1 g / L, 3 g / L, 5 g / L, 6 g / L, 8 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In some embodiments, the precipitant solution used in the co-precipitation process may be a sodium hydroxide solution.

[0019] In some embodiments, the complexing agent solution used in the co-precipitation process may be ammonia.

[0020] In some embodiments, the molar ratio of nickel to cobalt in the nickel-cobalt salt solution is 96:2 or higher, for example, 96:2, 96.5:1.5, 97:1 or 97.5:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In some embodiments, the particle size D50 of the nickel-cobalt precursor is 1.7 μm to 2.5 μm, for example, it can be 1.7 μm, 1.8 μm, 2 μm, 2.1 μm, 2.4 μm or 2.5 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In some embodiments, the preparation method of the carbon-doped nano-manganese oxide includes: mixing manganese sulfate solution, tea polyphenol solution and precipitant, aging, filtering and drying to obtain the carbon-doped nano-manganese oxide with a median particle size D50 of 12nm~28nm.

[0023] In some embodiments, the concentration of the manganese sulfate solution is 10 g / L to 70 g / L, for example, it can be 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L or 70 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In some embodiments, the concentration of the tea polyphenol solution is 5 g / L to 10 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] In some embodiments, the volume ratio of the manganese sulfate solution to the tea polyphenol solution is 8:1 to 30:1, for example, it can be 8:1, 15:1, 21:1, 25:1 or 30:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] In some embodiments, the amount of precipitant used is such that the pH of the system is 8 to 11, for example, 8, 9, 10 or 11, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0027] In some embodiments, the aging time is 10 min to 70 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min or 70 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] In some embodiments, in step (2), the ratio of the total molar amount of nickel and cobalt to the molar amount of manganese in the nickel-cobalt precursor and the carbon-doped nano-manganese oxide is 98:1.7 to 98:1.95, for example, it can be 98:1.7, 98:1.75, 98:1.8, 98:1.85, 98:1.9 or 98:1.95, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In some embodiments, if the total molar amount of nickel-cobalt precursor and carbon-doped nano-manganese oxide in step (2) is M, then the molar ratio of lithium to M in the lithium source is 1:1 to 1.08:1, for example, it can be 1:1, 1.02:1, 1.04:1, 1.05:1, 1.06:1 or 1.08:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] In some embodiments, the temperature of the first heat treatment is 720°C to 820°C, and the time is 6 hours to 12 hours.

[0031] The temperature of the first heat treatment is 750℃~870℃, for example, it can be 750℃, 770℃, 800℃, 850℃ or 870℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] The first heat treatment time is 6h to 12h, for example, it can be 6h, 8h, 9h, 10h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] In some embodiments, the total molar amount of nickel and cobalt in the sintering material is 98:1.8 to 98:2 in molar ratio with the manganese in the carbon-doped nano-manganese oxide in step (3). For example, it can be 98:1.8, 98:1.9 or 98:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] In some embodiments, the temperature of the second heat treatment is 730°C to 870°C, and the time is 2 hours to 8 hours.

[0035] The temperature of the second heat treatment is 730℃~870℃, for example, it can be 730℃, 760℃, 780℃, 800℃, 830℃ or 870℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] The second heat treatment time is 2h to 8h, for example, it can be 2h, 4h, 5h, 7h or 8h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] As a preferred embodiment of the preparation method provided in the first aspect of the present invention, the preparation method includes the following steps:

[0038] S1. Preparation of nickel-cobalt precursor by co-precipitation method: Co-precipitation reaction is carried out under the conditions of co-current mixing of nickel-cobalt salt solution, precipitant solution and complexing agent solution, pH value of 9~12, temperature of 20℃~80℃ and complexing agent concentration of 1g / L~10g / L to obtain nickel-cobalt precursor with particle size D50 of 1.7μm~2.5μm;

[0039] In the nickel-cobalt salt solution, the molar ratio of nickel to cobalt is 96:2 or higher; the precipitant solution is sodium hydroxide solution, and the complexing agent solution is ammonia water;

[0040] S2. Mix manganese sulfate solution with a concentration of 10 g / L to 70 g / L, tea polyphenol solution with a concentration of 5 g / L to 10 g / L, and sodium hydroxide solution. Aging for 10 min to 70 min, filtering and drying to obtain carbon-doped nano-manganese oxide with a median particle size D50 of 12 nm to 28 nm.

[0041] The amount of sodium hydroxide solution used is such that the pH value of the system is 8-11;

[0042] The volume ratio of the manganese sulfate solution to the tea polyphenol solution is 8:1 to 30:1;

[0043] S3, a mixed lithium source, the nickel-cobalt precursor and carbon-doped nano-manganese oxide, are subjected to a first heat treatment at 720℃~820℃ for 6h~12h in an air atmosphere to obtain a sintered material;

[0044] In the nickel-cobalt precursor and the carbon-doped nano-manganese oxide, the ratio of the total molar amount of nickel and cobalt to the molar amount of manganese is 98:1.7 to 98:1.95.

[0045] If the total molar amount of nickel-cobalt precursor and carbon-doped nano-manganese oxide is M, then the molar ratio of lithium to M in the lithium source is 1:1 to 1.08:1.

[0046] S4. Mix the calcined material with carbon-doped nano-manganese oxide and perform a second heat treatment at 730℃~870℃ for 2h~8h in a nitrogen atmosphere to obtain the ultra-high nickel single crystal cathode material.

[0047] The total molar amount of nickel and cobalt in the first sintering material is 98:1.8~98:2 compared with the molar ratio of manganese in the carbon-doped nano-manganese oxide in step (3).

[0048] Steps S1 and S2 are not in any particular order.

[0049] In a second aspect, the present invention provides an ultra-high nickel single crystal cathode material, which is prepared by the preparation method described in the first aspect.

[0050] Thirdly, the present invention provides a battery comprising the ultra-high nickel single crystal cathode material described in the second aspect;

[0051] The battery includes a solid-state battery.

[0052] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The preparation method provided by this invention first prepares a nickel-cobalt precursor, providing industrial feasibility of the process. Then, carbon-doped nano-manganese oxide is added stepwise during the first and second heat treatment stages, optimizing the process difficulty in the preparation of the single-crystal precursor, thereby reducing the sintering temperature and preventing severe lithium-nickel mixing due to excessive temperature. At the same time, carbon is directly coated during the second heat treatment while coating manganese, replacing some of the carbon black added during electrode preparation, thus improving the rate performance of the ultra-high nickel single-crystal cathode material. In addition, this invention uses tea polyphenols as a dispersant and stabilizer, resulting in low process cost and stability, better manganese oxide dispersion, and further improving the rate performance of the ultra-high nickel single-crystal cathode material by replacing some of the carbon black added during electrode preparation through carbon coating. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0057] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0059] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0060] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0061] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0062] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0063] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0064] Example 1

[0065] This embodiment provides a method for preparing an ultra-high nickel single-crystal cathode material, including the following steps:

[0066] S1. Preparation of nickel-cobalt precursor by co-precipitation method: Co-precipitation reaction was carried out under the conditions of co-current mixing of nickel-cobalt salt solution, precipitant solution and complexing agent solution, pH value of 10, temperature of 50℃ and complexing agent concentration of 5g / L to obtain nickel-cobalt precursor with particle size D50 of 2μm.

[0067] In the nickel-cobalt salt solution, the nickel salt is nickel sulfate and the cobalt salt is cobalt sulfate; and the molar ratio of nickel to cobalt is 96:2; the precipitant solution is sodium hydroxide solution and the complexing agent solution is ammonia water;

[0068] S2. Mix a 40 g / L manganese sulfate solution, an 8 g / L tea polyphenol (CAS: 84650-60-2) solution, and a sodium hydroxide solution, age for 40 min, filter, and dry to obtain carbon-doped nano-manganese oxide with a median particle size D50 of 20 nm.

[0069] The amount of sodium hydroxide solution used is such that the pH value of the system is 10;

[0070] The volume ratio of the manganese sulfate solution to the tea polyphenol solution is 20:1;

[0071] S3, a mixture of lithium carbonate, the nickel-cobalt precursor and carbon-doped nano-manganese oxide, is subjected to a first heat treatment at 760°C for 9 hours in an air atmosphere to obtain a sintered material;

[0072] In the nickel-cobalt precursor and the carbon-doped nano-manganese oxide, the ratio of the total molar amount of nickel and cobalt to the molar amount of manganese is 98:1.8.

[0073] If the total metal content of the nickel-cobalt precursor and carbon-doped nano-manganese oxide is M, then the molar ratio of lithium to M in the lithium source is 1.04:1.

[0074] S4. Mix the calcined material with carbon-doped nano-manganese oxide and perform a second heat treatment at 800°C for 5 hours in a nitrogen atmosphere to obtain the ultra-high nickel single crystal cathode material.

[0075] The total molar ratio of nickel and cobalt in the first sintering material to the molar ratio of manganese in the carbon-doped nano-manganese oxide in step (3) is 98:1.9.

[0076] Example 2

[0077] This embodiment provides a method for preparing an ultra-high nickel single-crystal cathode material, including the following steps:

[0078] S1. Preparation of nickel-cobalt precursor by co-precipitation method: Co-precipitation reaction was carried out under the conditions of co-current mixing of nickel-cobalt salt solution, precipitant solution and complexing agent solution, pH value of 9, temperature of 20℃ and complexing agent concentration of 1g / L to obtain nickel-cobalt precursor with particle size D50 of 1.7μm;

[0079] In the nickel-cobalt salt solution, the nickel salt is nickel sulfate and the cobalt salt is cobalt sulfate; and the molar ratio of nickel to cobalt is 96:2; the precipitant solution is sodium hydroxide solution and the complexing agent solution is ammonia water;

[0080] S2. Mix manganese sulfate solution with a concentration of 10 g / L, tea polyphenol solution with a concentration of 5 g / L and sodium hydroxide solution, age for 10 min, filter and dry to obtain carbon-doped nano-manganese oxide with a median particle size D50 of 12 nm.

[0081] The amount of sodium hydroxide solution used is such that the pH value of the system is 8;

[0082] The volume ratio of the manganese sulfate solution to the tea polyphenol solution is 8:1;

[0083] S3, a mixture of lithium carbonate, the nickel-cobalt precursor and carbon-doped nano-manganese oxide, is subjected to a first heat treatment at 720°C for 12 hours in an air atmosphere to obtain a sintered material;

[0084] In the nickel-cobalt precursor and the carbon-doped nano-manganese oxide, the ratio of the total molar amount of nickel and cobalt to the molar amount of manganese is 98:1.7.

[0085] If the total metal content of the nickel-cobalt precursor and carbon-doped nano-manganese oxide is M, then the molar ratio of lithium to M in the lithium source is 1:1.

[0086] S4. Mix the calcined material with carbon-doped nano-manganese oxide and perform a second heat treatment at 730°C for 8 hours in a nitrogen atmosphere to obtain the ultra-high nickel single crystal cathode material.

[0087] The total molar ratio of nickel and cobalt in the first sintering material to the molar ratio of manganese in the carbon-doped nano-manganese oxide in step (3) is 98:1.8.

[0088] Example 3

[0089] This embodiment provides a method for preparing an ultra-high nickel single-crystal cathode material, including the following steps:

[0090] S1. Preparation of nickel-cobalt precursor by co-precipitation method: Co-precipitation reaction was carried out under the conditions of co-current mixing of nickel-cobalt salt solution, precipitant solution and complexing agent solution, pH value of 12, temperature of 80℃ and complexing agent concentration of 10g / L to obtain nickel-cobalt precursor with particle size D50 of 2.5μm;

[0091] In the nickel-cobalt salt solution, the nickel salt is nickel sulfate and the cobalt salt is cobalt sulfate; and the molar ratio of nickel to cobalt is 96:2; the precipitant solution is sodium hydroxide solution and the complexing agent solution is ammonia water;

[0092] S2. Mix manganese sulfate solution with a concentration of 70 g / L, tea polyphenol solution with a concentration of 10 g / L and sodium hydroxide solution, age for 70 min, filter and dry to obtain carbon-doped nano-manganese oxide with a median particle size D50 of 28 nm.

[0093] The amount of sodium hydroxide solution used is such that the pH value of the system is 11;

[0094] The volume ratio of the manganese sulfate solution to the tea polyphenol solution is 30:1;

[0095] S3. Mix lithium carbonate, the nickel-cobalt precursor and carbon-doped nano-manganese oxide, and perform a first heat treatment at 820°C for 6 hours in an air atmosphere to obtain a sintered material.

[0096] In the nickel-cobalt precursor and the carbon-doped nano-manganese oxide, the ratio of the total molar amount of nickel and cobalt to the molar amount of manganese is 98:1.95.

[0097] If the total metal content of the nickel-cobalt precursor and carbon-doped nano-manganese oxide is M, then the molar ratio of lithium to M in the lithium source is 1.08:1.

[0098] S4. Mix the calcined material with carbon-doped nano-manganese oxide and perform a second heat treatment at 870°C for 2 hours in a nitrogen atmosphere to obtain the ultra-high nickel single crystal cathode material.

[0099] The total molar ratio of nickel and cobalt in the first sintering material to the molar ratio of manganese in the carbon-doped nano-manganese oxide in step (3) is 98:2.

[0100] Example 4

[0101] This embodiment provides a method for preparing an ultra-high nickel single crystal cathode material, which is the same as in Example 1 except that the temperature of the first heat treatment is 700°C.

[0102] Example 5

[0103] This embodiment provides a method for preparing an ultra-high nickel single crystal cathode material, which is the same as in Example 1 except that the temperature of the first heat treatment is 850°C.

[0104] Example 6

[0105] This embodiment provides a method for preparing an ultra-high nickel single crystal cathode material, which is the same as in Example 1 except that the temperature of the second heat treatment is 700°C.

[0106] Example 7

[0107] This embodiment provides a method for preparing an ultra-high nickel single crystal cathode material, which is the same as in Example 1 except that the temperature of the second heat treatment is 900°C.

[0108] Comparative Example 1

[0109] This comparative example provides a method for preparing a cathode material, including the following steps:

[0110] S1. Preparation of nickel-cobalt-manganese precursor by co-precipitation method: Co-precipitation reaction was carried out under the conditions of co-current mixing of nickel-cobalt-manganese salt solution, precipitant solution and complexing agent solution, pH value of 10, temperature of 50℃ and complexing agent concentration of 5g / L to obtain nickel-cobalt-manganese precursor with particle size D50 of 2μm.

[0111] In the nickel-cobalt-manganese salt solution, the nickel salt is nickel sulfate, the cobalt salt is cobalt sulfate, and the manganese salt is manganese sulfate; and the molar ratio of nickel, cobalt, and manganese is 96:2:1.8; the precipitant solution is sodium hydroxide solution, and the complexing agent solution is ammonia water;

[0112] S2, mixed lithium carbonate, and the nickel-cobalt-manganese precursor are subjected to a first heat treatment at 720°C for 12 hours in an air atmosphere to obtain the cathode material;

[0113] If the total metal content of the nickel-cobalt-manganese precursor is M, then the molar ratio of lithium to M in the lithium source is 1.04:1.

[0114] Performance Characterization

[0115] [Preparation of all-solid-state batteries]

[0116] Lithium-indium alloy was used as the negative electrode in the solid-state battery. After pressing the alloy sheet, it was attached to the surface of the stainless steel negative electrode block, and then a pressure of 150 MPa was applied using a hydraulic press. A 10 mm diameter polyoxymethylene sleeve was then fitted over it. 70 mg of LSPSC sulfide solid electrolyte was weighed and poured into the sleeve, and then a pressure of 100 MPa was applied to compact the electrolyte. The positive electrode material and LSPSC sulfide solid electrolyte were ground and mixed evenly in a mortar at a mass ratio of 7:3. A certain mass of composite positive electrode material was weighed and poured into the sleeve as the positive electrode material for the solid-state battery, and a 10 mm diameter stainless steel sheet was used as the current collector for the positive electrode. The mold battery was assembled and a pressure of 600 MPa was applied to form a sandwich structure. Finally, the battery was secured externally with stainless steel screws, maintaining a certain pressure during testing.

[0117] The results are shown in Table 1.

[0118] Table 1

[0119]

[0120] As can be seen from Examples 1 to 3 in Table 1, the ultra-high nickel single crystal cathode material provided by the present invention has excellent electrochemical performance. The initial discharge specific capacity at 0.1C all exceed 220mAh / g, the rate retention rate at 5C / 1C reaches more than 89%, the capacity retention rate at 1C 100 cycles is close to 88%, and the initial coulombic efficiency exceeds 82%, which can well meet the performance requirements of solid-state batteries.

[0121] A comparison of Examples 4 and 5 with Example 1 shows that both excessively high and low initial heat treatment temperatures degrade material performance. The initial discharge specific capacities at 0.1C in Examples 4 and 5 were 200.9 mAh / g and 186.7 mAh / g, respectively, lower than the 225.3 mAh / g in Example 1. The capacity retention rates after 100 cycles at 1C also decreased to 79.6% and 82.1%, respectively. This is because excessively low initial heat treatment temperatures lead to insufficient crystal development and poor uniformity of subsequent manganese oxide doping; excessively high temperatures cause single crystal particles to agglomerate, forming larger single crystals. Furthermore, excessively high temperatures also result in severe lithium-nickel mixing, thus affecting electrochemical performance.

[0122] A comparison of Examples 6 and 7 with Example 1 shows that the second heat treatment temperature affects the material properties. The rate retention rates of Examples 6 and 7 (5C / 1C) are only 81.2% and 82.3%, respectively, lower than the 89.6% of Example 1, and the initial coulombic efficiency is also slightly lower. This is because if the second heat treatment temperature is too low, the coated carbon cannot grow into the ideal crystal form, thus failing to effectively improve the rate performance; if the temperature is too high, the carbon coating layer will be over-carbonized or even fall off, and may also cause abnormal growth of single crystal particles beyond the 0.5μm~2μm adaptation range, exacerbating interface problems, and also causing lithium-nickel mixing in the material, seriously affecting the electrochemical performance.

[0123] A comparison of Comparative Example 1 and Example 1 shows that the material prepared using the traditional process without carbon-doped nano-manganese oxide exhibits significantly poorer performance. The initial discharge specific capacity at 0.1C of Comparative Example 1 (216.5 mAh / g) is lower than that of Example 1 (225.3 mAh / g), and its rate retention (88.3%) and cycle capacity retention (83.0%) are also lower. This is because the traditional process directly prepares the nickel-cobalt-manganese precursor, which suffers from manganese interference and poor precursor crystallinity. Furthermore, the lack of tea polyphenol-dispersed nano-manganese oxide leads to agglomeration problems, and the absence of a carbon coating layer to replace carbon black prevents optimization of ion transport channels, resulting in decreased capacity, rate capability, and cycle performance.

[0124] In summary, nickel accounts for more than 95% of the transition metal in current ultra-high nickel single crystal cathode materials. Since nickel and cobalt have very similar properties, only nickel and cobalt elements are precipitated during the co-precipitation process. Manganese oxide is added during the heat treatment process to obtain ultra-high nickel single crystal cathode materials. This can optimize the chemical precipitation process, eliminate the influence of manganese elements, and facilitate the large-scale production of precursors. Furthermore, due to the interface issues of solid-state batteries, it is usually necessary to control the single crystal particle size to be 0.5μm~2μm, so the added manganese oxide needs to reach the nanoscale. However, nano-manganese oxide is prone to agglomeration during the preparation process. The preparation method provided by this invention first prepares a nickel-cobalt precursor, providing industrial feasibility of the process. Then, carbon-doped nano-manganese oxide is added stepwise in the first and second heat treatment stages, optimizing the process difficulty in the preparation of the single crystal precursor, thereby reducing the sintering temperature and preventing severe lithium-nickel mixing in the material due to excessive temperature. At the same time, carbon is directly coated while coating manganese in the second heat treatment, replacing some of the carbon black added during the electrode preparation process, thus improving the rate performance of the ultra-high nickel single crystal cathode material. In addition, this invention uses tea polyphenols as a dispersant and stabilizer, which has low process cost and stability, better manganese oxide dispersion, and further improves the rate performance of the ultra-high nickel single crystal cathode material by directly replacing the carbon black added during the electrode preparation process through carbon coating.

[0125] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an ultra-high nickel single-crystal cathode material, characterized in that, The preparation method includes the following steps: (1) Preparation of nickel-cobalt precursor and carbon-doped nano-manganese oxide; (2) A mixture of lithium source, nickel-cobalt precursor and carbon-doped nano-manganese oxide is subjected to a first heat treatment in an oxygen-containing atmosphere to obtain a sintered material; The temperature of the first heat treatment is 720℃~820℃, and the time is 6h~12h; (3) Mix a calcined material with carbon-doped nano-manganese oxide and perform a second heat treatment in a protective atmosphere to obtain the ultra-high nickel single crystal cathode material; The second heat treatment is performed at a temperature of 730℃ to 870℃ for a duration of 2 hours to 8 hours.

2. The preparation method according to claim 1, characterized in that, The method for preparing the nickel-cobalt precursor includes a co-precipitation method; The coprecipitation method includes the following steps: A nickel-cobalt salt solution, a precipitant solution, and a complexing agent solution are mixed in parallel flow and co-precipitated to obtain the nickel-cobalt precursor.

3. The preparation method according to claim 2, characterized in that, The pH value of the coprecipitation reaction is 9~12; And / or, the temperature of the coprecipitation reaction is 20℃~80℃; And / or, during the coprecipitation reaction, the concentration of the complexing agent in the system is 1 g / L to 10 g / L.

4. The preparation method according to claim 2 or 3, characterized in that, In the nickel-cobalt salt solution, the molar ratio of nickel to cobalt is 96:2 or higher; And / or, the particle size D50 of the nickel-cobalt precursor is 1.7 μm to 2.5 μm.

5. The preparation method according to claim 1, characterized in that, The preparation method of the carbon-doped nano-manganese oxide includes: mixing manganese sulfate solution, tea polyphenol solution and precipitant, aging, filtering and drying to obtain the carbon-doped nano-manganese oxide with a median particle size D50 of 12nm~28nm.

6. The preparation method according to claim 5, characterized in that, The concentration of the manganese sulfate solution is 10 g / L to 70 g / L; And / or, the concentration of the tea polyphenol solution is 5 g / L to 10 g / L; And / or, the volume ratio of the manganese sulfate solution to the tea polyphenol solution is 8:1 to 30:

1.

7. The preparation method according to claim 5 or 6, characterized in that, The amount of precipitant used is such that the pH of the system is 8-11; And / or, the aging time is 10 min to 70 min.

8. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the total molar amount of nickel and cobalt to the molar amount of manganese in the nickel-cobalt precursor and the carbon-doped nano-manganese oxide is 98:1.7 to 98:1.

95. And / or, if the total molar amount of nickel-cobalt precursor and carbon-doped nano-manganese oxide in step (2) is M, then the molar ratio of lithium to M in the lithium source is 1:1~1.08:1; And / or, the total molar amount of nickel and cobalt in the sintering material is 98:1.8~98:2 compared with the molar ratio of manganese in the carbon-doped nano-manganese oxide in step (3).

9. A high-nickel single-crystal cathode material, characterized in that, The ultra-high nickel single crystal cathode material is prepared by the preparation method described in any one of claims 1 to 8.

10. A battery, characterized in that, The battery comprises the ultra-high nickel single crystal cathode material as described in claim 9; The battery includes a solid-state battery.

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