Modified high-nickel positive electrode material, preparation method, positive electrode sheet and solid-state lithium ion battery

Abstract

The application provides a modified high-nickel positive electrode material, a preparation method, a positive electrode sheet and a solid-state lithium ion battery. The preparation method comprises the following steps: continuously feeding mixed salt solution, complexing agent solution and precipitant solution into a bottom liquid to perform a first co-precipitation reaction to obtain an inner core; continuously feeding sodium metaaluminate solution, calcium chloride solution, complexing agent solution and precipitant solution to perform a second co-precipitation reaction to obtain a precursor with a calcium chloroaluminate coating layer on the surface; mixing a lithium source with the precursor, and calcining to obtain the modified high-nickel positive electrode material. In the application, the calcium chloroaluminate coating layer is generated in situ on the surface of the inner core, and is converted into a Li-Ca-O-Cl composite coating layer with good ion conductivity after lithium mixing and sintering, and uniform Al element doping is realized. The Al-containing composite coating layer has excellent chemical stability and structural stability, can effectively block the interface side reaction, and can improve the cycle stability and rate performance of the solid-state battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a modified high-nickel cathode material, its preparation method, cathode sheet, and solid-state lithium-ion battery. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, traditional liquid lithium-ion batteries face bottlenecks in energy density and safety. Solid-state batteries, which use non-flammable solid electrolytes instead of flammable organic liquid electrolytes, fundamentally solve the safety hazards of batteries and are expected to achieve higher energy densities, making them the development direction of next-generation lithium-ion batteries. However, the solid-solid contact between the cathode material and the solid electrolyte in solid-state batteries restricts their performance improvement. High-nickel ternary cathode materials (Ni content ≥90 at%) have advantages such as high specific capacity and low cost. However, in solid-state battery systems, the interface contact area between them and the solid electrolyte is small, the interface impedance is high, and they are prone to interfacial side reactions and structural degradation during charge and discharge, leading to a decrease in the cycle stability and rate performance of the battery, making it difficult to directly apply them to high-performance solid-state batteries.

[0003] To improve the interfacial contact performance between high-nickel ternary cathode materials and solid-state electrolytes, surface coating modification is currently the most commonly used technique. Existing technologies typically employ methods such as physical mixing, sol-gel, and atomic layer deposition to coat the surface of prepared high-nickel ternary cathode materials with a layer of inert or fast-ion conductor materials such as oxides, phosphates, or sulfides. For example, existing technologies disclose a technique of coating the surface of high-nickel cathode materials with aluminum-containing lithium metal compounds as a coating layer, which can suppress interfacial side reactions to some extent. However, these post-coating methods suffer from problems such as uneven coating layers, easy agglomeration, and weak adhesion to the substrate, leading to easy coating layer detachment during charge and discharge, and difficulty in forming a stable interface. Furthermore, most existing coating layers only provide physical barriers and cannot achieve elemental doping modification, making it difficult to solve the interfacial problems of high-nickel ternary materials in solid-state batteries.

[0004] Although some studies have attempted to use co-precipitation to prepare coatings in situ on the surface of high-nickel precursors to improve the uniformity and adhesion of the coatings, existing co-precipitation coatings cannot simultaneously achieve multi-element composite coatings and doping.

[0005] Therefore, providing a surface modification method that can significantly improve the interfacial contact performance between high-nickel ternary cathode materials and solid electrolytes is of great significance for promoting the practical application of high-nickel ternary materials in solid-state batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a modified high-nickel cathode material, its preparation method, a cathode sheet, and a solid-state lithium-ion battery. The present invention generates a calcium aluminochloride coating layer in situ on the core surface, which, after lithium mixing and sintering, is transformed into a Li-Ca-O-Cl composite coating layer with good ionic conductivity, while simultaneously achieving uniform Al doping. The aluminum-containing composite coating layer exhibits excellent chemical and structural stability, effectively blocking interfacial side reactions and improving the cycle stability and rate performance of the solid-state battery.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a modified high-nickel cathode material, the method comprising the following steps:

[0009] (1) A mixed salt solution, a complexing agent solution and a precipitant solution are introduced into the bottom liquid in parallel to carry out the first coprecipitation reaction and obtain the core;

[0010] (2) Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution and precipitant solution in parallel to carry out the second coprecipitation reaction to obtain a precursor with a calcium chloroaluminate coating layer on the surface;

[0011] (3) Mix the lithium source with the precursor and calcine to obtain the modified high-nickel cathode material.

[0012] This invention involves simultaneously adding sodium aluminate and calcium chloride solutions during the later stages of the co-precipitation reaction of a high-nickel ternary precursor to generate a calcium chloroaluminate coating layer in situ. After lithium mixing and sintering, this is transformed into a Li-Ca-O-Cl composite coating layer with excellent lithium-ion conductivity, and aluminum is uniformly distributed within this composite coating layer. The composite coating layer prepared by this method exhibits extremely strong adhesion to the high-nickel ternary matrix, effectively preventing coating detachment during charge and discharge processes. This significantly improves the solid-solid interface between the high-nickel ternary cathode material and the solid electrolyte, substantially reducing interfacial impedance. Simultaneously, the aluminum-containing Li-Ca-O-Cl composite coating layer itself possesses excellent chemical and structural stability, effectively blocking interfacial side reactions between the high-nickel ternary material and the solid electrolyte, and suppressing surface structural degradation of the high-nickel material during charge and discharge processes. This, in turn, significantly improves the cycle stability and rate performance of the solid-state battery.

[0013] In some embodiments, the temperature of the base liquid is 40°C to 80°C.

[0014] In some embodiments, the pH of the base solution is 11-12.

[0015] In some embodiments, the concentration of the complexing agent in the substrate is 0.2 mol / L to 0.5 mol / L.

[0016] In some embodiments, the metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts;

[0017] The nickel salt includes any one or a combination of at least two of nickel nitrate, nickel sulfate, or nickel chloride;

[0018] The cobalt salt includes any one or a combination of at least two of cobalt nitrate, cobalt sulfate, or cobalt chloride.

[0019] The manganese salt includes any one or a combination of at least two of manganese nitrate, manganese sulfate, or manganese chloride.

[0020] In some embodiments, the mixed salt solution has a molar ratio of nickel, cobalt and manganese of x:y:(1-xy), where x≥0.9, 0≤y≤0.1, and x+y=1.

[0021] In some embodiments, the total concentration of metal ions in the mixed salt solution is 2 mol / L to 4 mol / L.

[0022] In some embodiments, the concentration of the sodium aluminate solution is 0.2 mol / L to 0.4 mol / L.

[0023] In some embodiments, the concentration of the calcium chloride solution is 0.2 mol / L to 0.4 mol / L.

[0024] In some embodiments, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, citric acid, or sodium citrate.

[0025] In some embodiments, the precipitant solution is a sodium hydroxide solution with a concentration of 1 mol / L to 3 mol / L.

[0026] In some embodiments, the temperature of the first coprecipitation reaction is 40°C to 80°C.

[0027] In some embodiments, the pH value of the first coprecipitation reaction is 10.5 to 11.5.

[0028] In some embodiments, during the first coprecipitation, the concentration of the complexing agent in the system is 0.1 mol / L to 0.5 mol / L.

[0029] In some embodiments, the first coprecipitation is carried out under stirring conditions at a stirring speed of 200 r / min to 400 r / min.

[0030] In some embodiments, the median particle size D50 of the kernel is 6.5 μm to 10 μm.

[0031] In some embodiments, the pH value of the second coprecipitation reaction is 10.5 to 11.5.

[0032] In some embodiments, during the second coprecipitation, the concentration of the complexing agent in the system is 0.1 mol / L to 0.5 mol / L.

[0033] In some embodiments, the second coprecipitation is carried out under stirring conditions at a stirring speed of 200 r / min to 400 r / min.

[0034] In some embodiments, the mass of the calcium chloroaluminate coating is 0.5 wt% to 2 wt% of the precursor.

[0035] In some embodiments, the lithium source includes LiOH and / or Li2CO3.

[0036] In some embodiments, the molar ratio of the precursor to lithium in the lithium source is 1:1.02 to 1:1.05.

[0037] In some embodiments, the calcination includes: first heating to 450°C~550°C in an oxygen-containing atmosphere and holding at that temperature for 4h~6h; then heating to 700°C~900°C and holding at that temperature for 10h~16h.

[0038] In a second aspect, the present invention provides a modified high-nickel cathode material, which is prepared by the preparation method described in the first aspect.

[0039] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising a modified high-nickel positive electrode material prepared by the preparation method described in the first aspect, or comprising the modified high-nickel positive electrode material described in the second aspect.

[0040] Fourthly, the present invention provides a solid-state lithium-ion battery, the solid-state lithium-ion battery comprising the positive electrode sheet described in the third aspect.

[0041] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention involves simultaneously adding sodium aluminate and calcium chloride solutions during the later stages of the co-precipitation reaction of a high-nickel ternary precursor to generate a calcium chloroaluminate coating layer in situ. After lithium mixing and sintering, this is transformed into a Li-Ca-O-Cl composite coating layer with excellent lithium-ion conductivity, and aluminum is uniformly distributed within this composite coating layer. The composite coating layer prepared by this method exhibits extremely strong adhesion to the high-nickel ternary matrix, effectively preventing coating detachment during charge and discharge processes. This significantly improves the solid-solid interface between the high-nickel ternary cathode material and the solid electrolyte, substantially reducing interfacial impedance. Simultaneously, the aluminum-containing Li-Ca-O-Cl composite coating layer itself possesses excellent chemical and structural stability, effectively blocking interfacial side reactions between the high-nickel ternary material and the solid electrolyte, and suppressing surface structural degradation of the high-nickel material during charge and discharge processes. This, in turn, significantly improves the cycle stability and rate performance of the solid-state battery. Detailed Implementation

[0044] 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.

[0045] 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.

[0046] 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.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0048] 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.

[0049] 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.

[0050] 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."

[0051] 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.

[0052] 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.

[0053] An embodiment of the present invention provides a method for preparing a modified high-nickel cathode material, the method comprising the following steps:

[0054] (1) A mixed salt solution, a complexing agent solution and a precipitant solution are introduced into the bottom liquid in parallel to carry out the first coprecipitation reaction and obtain the core;

[0055] (2) Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution and precipitant solution in parallel to carry out the second coprecipitation reaction to obtain a precursor with a calcium chloroaluminate coating layer on the surface;

[0056] (3) Mix the lithium source with the precursor and calcine to obtain the modified high-nickel cathode material.

[0057] This invention involves simultaneously adding sodium aluminate and calcium chloride solutions during the later stages of the co-precipitation reaction of a high-nickel ternary precursor to generate a calcium chloroaluminate coating layer in situ. After lithium mixing and sintering, this is transformed into a Li-Ca-O-Cl composite coating layer with excellent lithium-ion conductivity, and aluminum is uniformly distributed within this composite coating layer. The composite coating layer prepared by this method exhibits extremely strong adhesion to the high-nickel ternary matrix, effectively preventing coating detachment during charge and discharge processes. This significantly improves the solid-solid interface between the high-nickel ternary cathode material and the solid electrolyte, substantially reducing interfacial impedance. Simultaneously, the aluminum-containing Li-Ca-O-Cl composite coating layer itself possesses excellent chemical and structural stability, effectively blocking interfacial side reactions between the high-nickel ternary material and the solid electrolyte, and suppressing surface structural degradation of the high-nickel material during charge and discharge processes. This, in turn, significantly improves the cycle stability and rate performance of the solid-state battery.

[0058] The base liquid in this invention is composed of a mixture of water, a precipitant solution, and a complexing agent solution.

[0059] In some embodiments, the temperature of the base liquid is 40°C to 80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] In some embodiments, the pH value of the substrate is 11 to 12, for example, it can be 11, 11.2, 11.5, 11.6, 11.8 or 12, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the concentration of the complexing agent in the substrate is 0.2 mol / L to 0.5 mol / L, for example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] In some embodiments, the metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts;

[0063] The nickel salt includes any one or a combination of at least two of nickel nitrate, nickel sulfate, or nickel chloride;

[0064] The cobalt salt includes any one or a combination of at least two of cobalt nitrate, cobalt sulfate, or cobalt chloride.

[0065] The manganese salt includes any one or a combination of at least two of manganese nitrate, manganese sulfate, or manganese chloride.

[0066] In some embodiments, the mixed salt solution has a molar ratio of nickel, cobalt and manganese of x:y:(1-xy), where x≥0.9, 0≤y≤0.1, and x+y=1.

[0067] In some embodiments, the total concentration of metal ions in the mixed salt solution is 2 mol / L to 4 mol / L, for example, it can be 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L or 4 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the concentration of the sodium aluminate solution is 0.2 mol / L to 0.4 mol / L, for example, it can be 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L or 0.4 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the concentration of the calcium chloride solution is 0.2 mol / L to 0.4 mol / L, for example, it can be 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L or 0.4 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In this invention, when sodium aluminate solution and calcium chloride solution are introduced in parallel, the molar ratio of sodium aluminate to calcium chloride can be 1.8:1 to 2.2:1, for example, 1.8:1, 1.9:1, 2:1, 2.1:1 or 2.2:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 2:1 being the preferred ratio.

[0071] In some embodiments, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, citric acid, or sodium citrate.

[0072] In some embodiments, the precipitant solution is a sodium hydroxide solution with a concentration of 1 mol / L to 3 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the temperature of the first coprecipitation reaction is 40°C to 80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] In some embodiments, the pH value of the first coprecipitation reaction is 10.5 to 11.5, for example, it can be 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4 or 11.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0075] In some embodiments, during the first coprecipitation, the concentration of the complexing agent in the system is 0.1 mol / L to 0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] In some embodiments, the first coprecipitation is carried out under stirring conditions of 200 r / min to 400 r / min, for example, 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0077] In some embodiments, the median particle size D50 of the kernel is 6.5 μm to 10 μm, for example, it can be 6.5, 7, 7.5, 8 μm, 9 μm or 10 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, the temperature of the second coprecipitation reaction is 40°C to 80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, the pH value of the second coprecipitation reaction is 10.5 to 11.5, for example, it can be 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4 or 11.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, during the second coprecipitation, the concentration of the complexing agent in the system is 0.1 mol / L to 0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] In some embodiments, the second coprecipitation is carried out under stirring conditions of 200 r / min to 400 r / min, for example, 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, the mass of the calcium chloroaluminate coating layer is 0.5wt% to 2wt% of the precursor, for example, it can be 0.5wt%, 0.6wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.6wt%, 1.8wt% or 2wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the lithium source includes LiOH and / or Li2CO3.

[0084] In some embodiments, the molar ratio of the precursor to lithium in the lithium source is 1:1.02 to 1:1.05, for example, it can be 1:1.02, 1:1.03, 1:1.04 or 1:1.05, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0085] In some embodiments, the calcination includes: first heating to 450°C~550°C in an oxygen-containing atmosphere and holding at that temperature for 4h~6h; then heating to 700°C~900°C and holding at that temperature for 10h~16h.

[0086] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes:

[0087] S1. Water, precipitant solution and complexing agent solution are added to the reaction vessel to prepare a bottom solution with a temperature of 40℃~80℃, a pH value of 11~12 and a complexing agent concentration of 0.2mol / L~0.5mol / L.

[0088] S2. A mixed salt solution, complexing agent solution and precipitant solution are introduced into the bottom liquid in parallel to carry out the first coprecipitation reaction, and a kernel with a median particle size D50 of 6.5 μm to 10 μm is obtained.

[0089] The metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts, and the molar ratio of nickel, cobalt, and manganese is x:y:(1-xy), where x≥0.9, 0≤y≤0.1, and x+y=1; the total concentration of metal ions in the mixed salt solution is 2mol / L~4mol / L.

[0090] The temperature of the first coprecipitation reaction is 40℃~80℃, the pH value is 10.5~11.5, and the concentration of the complexing agent is 0.1mol / L~0.5mol / L; the first coprecipitation is carried out under stirring conditions of 200r / min~400r / min.

[0091] S3. Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution and precipitant solution in parallel to carry out the second coprecipitation reaction to obtain a precursor with a calcium chloroaluminate coating layer on the surface.

[0092] The concentration of the sodium aluminate solution is 0.2 mol / L to 0.4 mol / L; the concentration of the calcium chloride solution is 0.2 mol / L to 0.4 mol / L; the molar ratio of sodium aluminate to calcium chloride is 2:1.

[0093] The second coprecipitation reaction was carried out at a temperature of 40℃~80℃, a pH value of 10.5~11.5, and a complexing agent concentration of 0.1mol / L~0.5mol / L; the second coprecipitation was carried out under stirring conditions of 200r / min~400r / min.

[0094] The mass of the calcium chloroaluminate coating layer is 0.5wt%~2wt% of the precursor;

[0095] S4. The mixed lithium source and the precursor are calcined to obtain the modified high-nickel cathode material;

[0096] The lithium source includes LiOH and / or Li2CO3;

[0097] The molar ratio of the precursor to lithium in the lithium source is 1:1.02 to 1:1.05;

[0098] The calcination process includes: first, heating to 450℃~550℃ in an oxygen-containing atmosphere and holding at that temperature for 4h~6h; then heating to 700℃~900℃ and holding at that temperature for 10h~16h.

[0099] One embodiment of the present invention provides a modified high-nickel cathode material, which is prepared by the preparation method described in any embodiment.

[0100] The present invention provides a positive electrode sheet, which includes a modified high-nickel positive electrode material prepared by the preparation method described in any embodiment, or includes a modified high-nickel positive electrode material described in any embodiment.

[0101] The present invention provides a solid-state lithium-ion battery, wherein the solid-state lithium-ion battery includes the positive electrode.

[0102] Example 1

[0103] This embodiment provides a method for preparing a modified high-nickel cathode material, including the following steps:

[0104] S1. Add water, precipitant solution (2 mol / L sodium hydroxide solution) and complexing agent solution (ammonia) to the reactor to prepare a bottom solution with a temperature of 60℃, a pH value of 11.5 and a complexing agent concentration of 0.3 mol / L.

[0105] S2. A mixed salt solution, a complexing agent solution (ammonia water), and a precipitant solution (2 mol / L sodium hydroxide solution) are introduced concurrently into the bottom liquid to carry out the first coprecipitation reaction, resulting in a core with a median particle size D50 of 8 μm.

[0106] The metal salts in the mixed salt solution are nickel sulfate, cobalt sulfate, and manganese sulfate, and the molar ratio of nickel, cobalt, and manganese is 0.9:0.05:0.05; the total concentration of metal ions in the mixed salt solution is 3 mol / L.

[0107] The first coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, and a complexing agent concentration of 0.3 mol / L; the first coprecipitation was carried out under stirring conditions at a stirring speed of 300 r / min.

[0108] S3. Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution (ammonia water) and precipitant solution (2 mol / L sodium hydroxide solution) in parallel to carry out the second coprecipitation reaction and obtain the precursor with a calcium chloroaluminate coating layer on the surface.

[0109] The concentration of the sodium aluminate solution is 0.3 mol / L; the concentration of the calcium chloride solution is 0.3 mol / L; the molar ratio of sodium aluminate to calcium chloride is 2:1;

[0110] The second coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, and a complexing agent concentration of 0.3 mol / L; the second coprecipitation was carried out under stirring conditions at a stirring speed of 300 r / min.

[0111] The mass of the calcium chloroaluminate coating layer is 1 wt% of the precursor.

[0112] S4. The mixed lithium source and the precursor are calcined to obtain the modified high-nickel cathode material;

[0113] The lithium source is LiOH;

[0114] The molar ratio of the precursor to lithium in the lithium source is 1:1.03;

[0115] The calcination process includes: first heating to 500°C in an air atmosphere and holding at that temperature for 5 hours; then heating to 800°C and holding at that temperature for 12 hours.

[0116] Example 2

[0117] This embodiment provides a method for preparing a modified high-nickel cathode material, including the following steps:

[0118] S1. Add water, precipitant solution (1 mol / L sodium hydroxide solution) and complexing agent solution (ammonia) to the reaction vessel to prepare a bottom solution with a temperature of 40℃, a pH value of 11 and a complexing agent concentration of 0.2 mol / L.

[0119] S2. A mixed salt solution, a complexing agent solution (ammonia water), and a precipitant solution (1 mol / L sodium hydroxide solution) are introduced concurrently into the bottom liquid to carry out the first coprecipitation reaction, resulting in a core with a median particle size D50 of 6.5 μm.

[0120] The metal salts in the mixed salt solution are nickel sulfate, cobalt sulfate, and manganese sulfate, and the molar ratio of nickel, cobalt, and manganese is 0.9:0.05:0.05; the total concentration of metal ions in the mixed salt solution is 2 mol / L.

[0121] The first coprecipitation reaction was carried out at a temperature of 40°C, a pH of 10.5, and a complexing agent concentration of 0.1 mol / L; the first coprecipitation was carried out under stirring conditions at a stirring speed of 200 r / min.

[0122] S3. Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution (ammonia water) and precipitant solution (1 mol / L sodium hydroxide solution) in parallel to carry out the second coprecipitation reaction and obtain the precursor with a calcium chloroaluminate coating layer on the surface.

[0123] The concentration of the sodium aluminate solution is 0.2 mol / L; the concentration of the calcium chloride solution is 0.2 mol / L; the molar ratio of sodium aluminate to calcium chloride is 2:1;

[0124] The second coprecipitation reaction was carried out at a temperature of 40°C, a pH of 10.5, and a complexing agent concentration of 0.1 mol / L; the second coprecipitation was carried out under stirring conditions at a stirring speed of 200 r / min.

[0125] The mass of the calcium chloroaluminate coating is 0.5 wt% of the precursor.

[0126] S4. The mixed lithium source and the precursor are calcined to obtain the modified high-nickel cathode material;

[0127] The lithium source is LiOH;

[0128] The molar ratio of the precursor to lithium in the lithium source is 1:1.02;

[0129] The calcination process includes: first heating to 450°C in an air atmosphere and holding for 6 hours; then heating to 700°C and holding for 16 hours.

[0130] Example 3

[0131] This embodiment provides a method for preparing a modified high-nickel cathode material, including the following steps:

[0132] S1. Add water, precipitant solution (3 mol / L sodium hydroxide solution) and complexing agent solution (ammonia) to the reactor to prepare a bottom solution with a temperature of 80℃, a pH value of 12 and a complexing agent concentration of 0.5 mol / L.

[0133] S2. A mixed salt solution, a complexing agent solution (ammonia water), and a precipitant solution (3 mol / L sodium hydroxide solution) are introduced concurrently into the bottom liquid to carry out the first coprecipitation reaction, resulting in a core with a median particle size D50 of 10 μm.

[0134] The metal salts in the mixed salt solution are nickel sulfate, cobalt sulfate, and manganese sulfate, and the molar ratio of nickel, cobalt, and manganese is 0.9:0.05:0.05; the total concentration of metal ions in the mixed salt solution is 4 mol / L.

[0135] The first coprecipitation reaction was carried out at a temperature of 80°C, a pH of 11.5, and a complexing agent concentration of 0.5 mol / L; the first coprecipitation was carried out under stirring conditions at a stirring speed of 400 r / min.

[0136] S3. Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution (ammonia water) and precipitant solution (3mol / L sodium hydroxide solution) in parallel to carry out the second coprecipitation reaction and obtain the precursor with a calcium chloroaluminate coating layer on the surface.

[0137] The concentration of the sodium aluminate solution is 0.4 mol / L; the concentration of the calcium chloride solution is 0.4 mol / L; the molar ratio of sodium aluminate to calcium chloride is 2:1;

[0138] The second coprecipitation reaction was carried out at a temperature of 80°C, a pH of 10.5, and a complexing agent concentration of 0.1 mol / L; the second coprecipitation was carried out under stirring conditions at a stirring speed of 400 r / min.

[0139] The mass of the calcium chloroaluminate coating layer is 2 wt% of the precursor.

[0140] S4. The mixed lithium source and the precursor are calcined to obtain the modified high-nickel cathode material;

[0141] The lithium source is LiOH;

[0142] The molar ratio of the precursor to lithium in the lithium source is 1:1.05;

[0143] The calcination process includes: first heating to 550°C in an air atmosphere and holding for 4 hours; then heating to 900°C and holding for 10 hours.

[0144] Example 4

[0145] This embodiment provides a method for preparing a modified high-nickel cathode material. Except that the mass of the calcium chloroaluminate coating layer is 0.1 wt% of the precursor, the rest is the same as in Example 1.

[0146] Example 5

[0147] This embodiment provides a method for preparing a modified high-nickel cathode material. Except that the mass of the calcium chloroaluminate coating layer is 2.5 wt% of the precursor, the rest is the same as in Example 1.

[0148] Comparative Example 1

[0149] This comparative example provides a method for preparing a modified high-nickel cathode material. Compared with Example 1, this comparative example does not use sodium aluminate solution and includes the following steps:

[0150] S1. Add water, precipitant solution (2 mol / L sodium hydroxide solution) and complexing agent solution (ammonia) to the reactor to prepare a bottom solution with a temperature of 60℃, a pH value of 11.5 and a complexing agent concentration of 0.3 mol / L.

[0151] S2. A mixed salt solution, a complexing agent solution (ammonia water), and a precipitant solution (2 mol / L sodium hydroxide solution) are introduced concurrently into the bottom liquid to carry out the first coprecipitation reaction, resulting in a core with a median particle size D50 of 10 μm.

[0152] The metal salts in the mixed salt solution are nickel sulfate, cobalt sulfate, and manganese sulfate, and the molar ratio of nickel, cobalt, and manganese is 0.9:0.05:0.05; the total concentration of metal ions in the mixed salt solution is 3 mol / L.

[0153] The first coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, and a complexing agent concentration of 0.3 mol / L; the first coprecipitation was carried out under stirring conditions at a stirring speed of 300 r / min.

[0154] S3. Continue to introduce calcium chloride solution, complexing agent solution (ammonia water) and precipitant solution (2 mol / L sodium hydroxide solution) in parallel to carry out the second coprecipitation reaction and obtain a precursor with a coating layer on the surface;

[0155] The concentration of the calcium chloride solution is 0.3 mol / L;

[0156] The second coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, and a complexing agent concentration of 0.3 mol / L; the second coprecipitation was carried out under stirring conditions at a stirring speed of 300 r / min.

[0157] The mass of the coating layer is 1 wt% of the precursor.

[0158] S4. The mixed lithium source and the precursor are calcined to obtain the modified high-nickel cathode material;

[0159] The lithium source is LiOH;

[0160] The molar ratio of the precursor to lithium in the lithium source is 1:1.03;

[0161] The calcination process includes: first heating to 500°C in an air atmosphere and holding at that temperature for 5 hours; then heating to 800°C and holding at that temperature for 12 hours.

[0162] Comparative Example 2

[0163] This comparative example provides a method for preparing a modified high-nickel cathode material. Compared with Example 1, this comparative example does not use calcium chloride solution and includes the following steps:

[0164] S1. Add water, precipitant solution (2 mol / L sodium hydroxide solution) and complexing agent solution (ammonia) to the reactor to prepare a bottom solution with a temperature of 60℃, a pH value of 11.5 and a complexing agent concentration of 0.3 mol / L.

[0165] S2. A mixed salt solution, a complexing agent solution (ammonia water), and a precipitant solution (2 mol / L sodium hydroxide solution) are introduced concurrently into the bottom liquid to carry out the first coprecipitation reaction, resulting in a core with a median particle size D50 of 10 μm.

[0166] The metal salts in the mixed salt solution are nickel sulfate, cobalt sulfate, and manganese sulfate, and the molar ratio of nickel, cobalt, and manganese is 0.9:0.05:0.05; the total concentration of metal ions in the mixed salt solution is 3 mol / L.

[0167] The first coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, and a complexing agent concentration of 0.3 mol / L; the first coprecipitation was carried out under stirring conditions at a stirring speed of 300 r / min.

[0168] S3. Continue to introduce sodium aluminate solution, complexing agent solution (ammonia water) and precipitant solution (2 mol / L sodium hydroxide solution) in parallel to carry out the second coprecipitation reaction and obtain a precursor with a coating layer on the surface.

[0169] The concentration of the sodium aluminate solution is 0.2 mol / L;

[0170] The second coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, and a complexing agent concentration of 0.3 mol / L; the second coprecipitation was carried out under stirring conditions at a stirring speed of 300 r / min.

[0171] The mass of the coating layer is 1 wt% of the precursor.

[0172] S4. The mixed lithium source and the precursor are calcined to obtain the modified high-nickel cathode material;

[0173] The lithium source is LiOH;

[0174] The molar ratio of the precursor to lithium in the lithium source is 1:1.03;

[0175] The calcination process includes: first heating to 500°C in an air atmosphere and holding at that temperature for 5 hours; then heating to 800°C and holding at that temperature for 12 hours.

[0176] Performance Characterization

[0177] The high-nickel ternary cathode material, Li6PS5Cl sulfide solid electrolyte, and conductive agent vapor-grown carbon fiber (VGCF) prepared in the above embodiments and comparative examples were mixed at a mass ratio of 70:28:2 and pressed at 300 MPa for 3 min to serve as the cathode. The Li6PS5Cl sulfide solid electrolyte was used as the electrolyte layer and pressed at 300 MPa for 3 min. The Li-In alloy was used as the anode. After the battery was assembled, the pressure was maintained at 20 MPa. All operations were performed in an argon atmosphere glove box.

[0178] At 25℃, 2.8V~4.3V, the cycle capacity retention rate was tested at a rate of 0.2C for 100 cycles. The rate performance test was conducted at current densities of 0.1C, 1C, 2C and 5C for 5 cycles each, and the discharge specific capacity at different rates was recorded. The results of the electrochemical performance test are shown in Table 1.

[0179] Table 1

[0180]

[0181] As can be seen from Examples 1 to 3 in Table 1, the Li-Ca-O-Cl coated modified high-nickel ternary cathode material provided by the present invention can significantly improve the cycle stability and rate performance of solid-state batteries at the same time, and is fully adapted to the high-performance application requirements of solid-state batteries.

[0182] Comparison of Comparative Examples 1 and 2 with Example 1 shows that when only calcium chloride (Comparative Example 1) is used, only a single calcium oxide coating layer can be formed after sintering, which has poor lithium-ion conductivity and cannot effectively reduce interfacial impedance. When only sodium aluminate (Comparative Example 2) is used, only a single aluminum oxide coating layer can be formed after sintering, which has poor chemical compatibility with Li6PS5Cl sulfide solid electrolyte and is prone to interfacial side reactions during charge and discharge. Neither of them can simultaneously improve cycle stability and rate performance.

[0183] As can be seen from the comparison between Example 4 and Example 1, when the coating amount is only 0.1wt%, a continuous and complete coating layer cannot be formed on the surface of the high-nickel ternary precursor, and a large number of exposed active sites exist. During the charge and discharge process, severe interfacial side reactions will occur between the high-nickel material and the solid electrolyte, resulting in a sharp increase in interfacial impedance. Therefore, the cycle capacity retention rate is only 90.12%, and the rate performance also drops significantly.

[0184] A comparison of Example 5 and Example 1 shows that when the coating amount reaches 2.5wt%, the excessively thick Li-Ca-O-Cl coating layer increases the resistance to lithium-ion transport, resulting in a significant reduction in the first discharge specific capacity of the cathode material to 215.4mAh / g. At the same time, the lithium-ion transport efficiency at high rates is also significantly affected, with a 5C discharge specific capacity of only 122.63mAh / g, which cannot meet the requirements of high-rate applications.

[0185] In summary, this invention, by simultaneously adding sodium aluminate solution and calcium chloride solution during the later stage of the co-precipitation reaction of the high-nickel ternary precursor, generates a calcium chloroaluminate coating layer in situ. After lithium mixing and sintering, this is transformed into a Li-Ca-O-Cl composite coating layer with good lithium-ion conductivity, and aluminum is uniformly distributed in this composite coating layer. The composite coating layer prepared by this method has extremely strong adhesion to the high-nickel ternary matrix, effectively preventing coating layer detachment during charge and discharge, significantly improving the solid-solid contact interface between the high-nickel ternary cathode material and the solid electrolyte, and greatly reducing interfacial impedance. At the same time, the aluminum-containing Li-Ca-O-Cl composite coating layer itself has excellent chemical and structural stability, effectively blocking interfacial side reactions between the high-nickel ternary material and the solid electrolyte, and inhibiting the surface structure degradation of the high-nickel material during charge and discharge, thereby significantly improving the cycle stability and rate performance of the solid-state battery.

[0186] 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 a modified high-nickel cathode material, characterized in that, The preparation method includes the following steps: (1) A mixed salt solution, a complexing agent solution and a precipitant solution are introduced into the bottom liquid in parallel to carry out the first coprecipitation reaction and obtain the core; (2) Continue to introduce sodium aluminate solution, calcium chloride solution, complexing agent solution and precipitant solution in parallel to carry out the second coprecipitation reaction to obtain a precursor with a calcium chloroaluminate coating layer on the surface; (3) Mix the lithium source with the precursor and calcine to obtain the modified high-nickel cathode material.

2. The preparation method according to claim 1, characterized in that, The temperature of the base liquid is 40℃~80℃; And / or, the pH of the base solution is 11-12; And / or, the concentration of the complexing agent in the substrate is 0.2 mol / L to 0.5 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that, The metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts; The nickel salt includes any one or a combination of at least two of nickel nitrate, nickel sulfate, or nickel chloride; The cobalt salt includes any one or a combination of at least two of cobalt nitrate, cobalt sulfate, or cobalt chloride. The manganese salt includes any one or a combination of at least two of manganese nitrate, manganese sulfate, or manganese chloride.

4. The preparation method according to claim 3, characterized in that, The mixed salt solution has a molar ratio of nickel, cobalt and manganese of x:y:(1-xy), where x≥0.9, 0≤y≤0.1, and x+y=1. And / or, the total concentration of metal ions in the mixed salt solution is 2 mol / L to 4 mol / L; And / or, the concentration of the sodium aluminate solution is 0.2 mol / L to 0.4 mol / L; And / or, the concentration of the calcium chloride solution is 0.2 mol / L to 0.4 mol / L; And / or, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, citric acid, or sodium citrate; And / or, the precipitant solution is a sodium hydroxide solution with a concentration of 1 mol / L to 3 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The temperature of the first coprecipitation reaction is 40℃~80℃; And / or, the pH value of the first coprecipitation reaction is 10.5~11.5; And / or, during the first coprecipitation, the concentration of the complexing agent in the system is 0.1 mol / L to 0.5 mol / L; And / or, the first coprecipitation is carried out under stirring conditions with a stirring speed of 200 r / min to 400 r / min; And / or, the median particle size D50 of the kernel is 6.5 μm to 10 μm.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The pH value of the second coprecipitation reaction is 10.5~11.5; And / or, during the second coprecipitation, the concentration of the complexing agent in the system is 0.1 mol / L to 0.5 mol / L; And / or, the second coprecipitation is carried out under stirring conditions at a stirring speed of 200 r / min to 400 r / min; And / or, the mass of the calcium chloroaluminate coating layer is 0.5wt% to 2wt% of the precursor.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The lithium source includes LiOH and / or Li2CO3; And / or, the molar ratio of the precursor to lithium in the lithium source is 1:1.02 to 1:1.05; And / or, the calcination includes: in an oxygen-containing atmosphere, first heating to 450℃~550℃ and holding for 4h~6h; then heating to 700℃~900℃ and holding for 10h~16h.

8. A modified high-nickel cathode material, characterized in that, The modified high-nickel cathode material is prepared by the preparation method described in any one of claims 1 to 7.

9. A positive electrode plate, characterized in that, The positive electrode sheet includes the modified high-nickel positive electrode material prepared by the preparation method according to any one of claims 1 to 7, or includes the modified high-nickel positive electrode material according to claim 8.

10. A solid-state lithium-ion battery, characterized in that, The solid-state lithium-ion battery includes the positive electrode sheet as described in claim 9.

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