Composite modified lithium-rich manganese-based positive electrode material, preparation method and positive electrode

Abstract

This invention relates to a composite modified lithium-rich manganese-based cathode material, its preparation method, and the cathode itself. The preparation method includes the following steps: a nickel-cobalt-manganese mixed salt solution, a precipitant solution, and a first complexing agent solution are simultaneously introduced into a bottom solution to perform a first co-precipitation reaction, obtaining a lithium-rich nickel-cobalt-manganese precursor core; the introduction of the nickel-cobalt-manganese mixed salt solution and the first complexing agent solution is stopped, while a doped mixed salt solution and a second complexing agent solution are simultaneously introduced to perform a second co-precipitation reaction, obtaining a doped core-shell precursor; a lithium source is mixed with the obtained doped core-shell precursor, and a first calcination is performed to obtain a doped core-shell cathode material; a coating material is mixed with the doped core-shell cathode material, and a second calcination is performed to form a coating layer, obtaining the composite modified lithium-rich manganese-based cathode material. The composite modified lithium-rich manganese-based cathode material provided by this invention employs a synergistic dual strategy of doping and coating, solving material structure, interface, and kinetic defects, thereby suppressing voltage decay and improving cycle and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to an electrode material, particularly to a composite modified lithium-rich manganese-based cathode material, its preparation method, and the cathode itself. Background Technology

[0002] With the continuous increase in demand for high-energy-density lithium batteries from fields such as new energy vehicles and large-scale energy storage, lithium-rich manganese-based cathode materials have become one of the core candidates for next-generation high-energy-density lithium battery cathode materials. However, the performance degradation problem faced by this material during actual cycling severely restricts its commercialization process. Even under normal charge-discharge conditions, the capacity retention rate is often less than 70% after 500 cycles, accompanied by significant voltage decay, which directly affects the energy output stability and lifespan of the battery.

[0003] In-depth research shows that the performance degradation of lithium-rich manganese-based materials stems from the coupling effect of multiple failure mechanisms: At the bulk level, during long-term charge and discharge, Li⁺ and transition metal ions are prone to cation mixing, which disrupts the orderliness of the layered crystal structure. At the same time, high voltage can induce irreversible phase transitions of the layered structure to the spinel or rock salt phase, leading to an imbalance in lattice volume shrinkage / expansion, which further exacerbates the cracking of the bulk structure. At the interface level, active oxygen atoms on the material surface are prone to redox reactions with carbonate electrolytes, generating an unstable solid electrolyte interphase (SEI) film. This is accompanied by the continuous loss of oxygen, which not only destroys the integrity of the bulk structure but also causes the dissolution of transition metal ions. The dissolved ions migrate with the electrolyte to the negative electrode and deposit, forming "dead lithium" or exacerbating the corrosion of the negative electrode, creating a vicious cycle of interface failure.

[0004] To address the aforementioned issues, existing technologies have developed single modification methods, such as bulk doping, surface coating, or structural reconstruction. However, single modification methods have significant limitations: while simple bulk doping can improve bulk structural stability, it cannot suppress interfacial oxygen loss and electrolyte corrosion; simple surface coating can protect the interface, but it is difficult to solve the bulk phase transition problem, and excessively thick coating layers can increase ion transport resistance, leading to a decrease in rate performance; some structural reconstruction methods are difficult to scale up due to complex preparation processes and poor doping / coating uniformity. In addition, some single modification methods can also cause new side effects, such as the introduction of high-valence metal ion doping, which may reduce the specific capacity of the material, further highlighting the limitations of single modification strategies in solving the multiple failure problems of lithium-rich manganese-based materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a composite modified lithium-rich manganese-based cathode material, its preparation method, and the cathode itself. The composite modified lithium-rich manganese-based cathode material provided by the present invention employs a synergistic dual strategy of doping and coating to solve defects in material structure, interface, and kinetics, thereby suppressing voltage decay and improving cycle and rate performance.

[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 a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0008] (1) A nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution are introduced into the bottom liquid in parallel to carry out the first coprecipitation reaction to obtain the lithium-rich nickel-cobalt-manganese precursor core;

[0009] (2) Stop the flow of nickel-cobalt-manganese mixed salt solution and first complexing agent solution, and simultaneously start the parallel flow of doped mixed salt solution and second complexing agent solution to carry out the second coprecipitation reaction and obtain doped core-shell precursor;

[0010] (3) Mix the lithium source with the doped core-shell precursor obtained in step (2), and calcine the mixture to obtain the doped core-shell cathode material.

[0011] (4) The coating material is mixed with the doped core-shell cathode material described in step (3), and a second calcination is performed to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material.

[0012] The preparation method provided by this invention ensures the uniformity of doping by using a mixed salt, and the doped metal ions can preferentially occupy the metal sites in the precursor lattice, hindering the transition metal ions (Mn) from being present. 2+ And / or Ni 2+ The migration channels of ) play a role in structural anchoring; the low-valence element Mg in the doped mixed salt solution 2+ With high-priced element Ti 4+ It can optimize the charge distribution within the crystal lattice, reduce the generation of oxygen vacancies, and maintain the long-term stability of the layered structure; the use of coating materials can alleviate interfacial stress, form a dual protection of doping and coating, and comprehensively improve the electrochemical performance and cycle stability of the material.

[0013] In one embodiment of the present invention, the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide.

[0014] In one embodiment of the present invention, the concentration of the precipitant in the precipitant solution is 28wt% to 35wt%, for example, it can be 28wt%, 30wt%, 32wt%, 34wt% or 35wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] In one embodiment of the present invention, the first complexing agent in the first complexing agent solution is any one of ammonia, oxalic acid, citric acid, sodium tartrate, or EDTA.

[0016] In one embodiment of the present invention, the second complexing agent in the second complexing agent solution includes any two of ammonia, citric acid, oxalic acid, tartaric acid, or EDTA, and includes EDTA.

[0017] In one embodiment of the present invention, the second complexing agent in the second complexing agent solution comprises ammonia and EDTA in a mass ratio of 1:1 to 10:1, or comprises oxalic acid and EDTA in a mass ratio of 1:1 to 10:1.

[0018] The mass ratio of ammonia to EDTA is 1:1 to 10:1, for example, it can be 1:1, 3:1, 5:1, 6:1, 8:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] The mass ratio of oxalic acid to EDTA is 1:1 to 10:1, for example, it can be 1:1, 3:1, 5:1, 6:1, 8:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] In one embodiment of the present invention, the molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is x. a :y a :z a , where x a +y a +z a =1, z a ≥0.6.

[0021] In one embodiment of the present invention, the nickel salt in the nickel-cobalt-manganese mixed salt solution includes any one or a combination of at least two of nickel chloride, nickel sulfate, or nickel nitrate. Typical but non-limiting combinations include a combination of nickel chloride and nickel sulfate, a combination of nickel chloride and nickel nitrate, a combination of nickel sulfate and nickel nitrate, or a combination of nickel chloride, nickel sulfate, and nickel nitrate.

[0022] The cobalt salt in the nickel-cobalt-manganese mixed salt solution includes any one or a combination of at least two of cobalt chloride, cobalt sulfate, or cobalt nitrate. Typical but non-limiting combinations include combinations of cobalt chloride and cobalt sulfate, cobalt chloride and cobalt nitrate, cobalt sulfate and cobalt nitrate, or cobalt chloride, cobalt sulfate, and cobalt nitrate.

[0023] The manganese salt in the nickel-cobalt-manganese mixed salt solution includes any one or a combination of at least two of manganese chloride, manganese sulfate, or manganese nitrate. Typical but non-limiting combinations include manganese chloride and manganese sulfate, manganese chloride and manganese nitrate, manganese sulfate and manganese nitrate, or manganese chloride, manganese sulfate, and manganese nitrate.

[0024] In one embodiment of the present invention, the concentration of the nickel-cobalt-manganese mixed salt solution is 85 g / L to 115 g / L, for example, it can be 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L or 115 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] In one embodiment of the present invention, the cations in the doped mixed salt solution include nickel, cobalt, manganese, magnesium, titanium, and a doped metal element M, wherein the doped metal M includes Y and / or Zr.

[0026] In one embodiment of the present invention, the molar ratio of nickel, cobalt, manganese, dopant metal M, magnesium, and titanium in the doped mixed salt solution is x. b :y b :z b :m:n:w, where x b +y b +z b =1, z b ≥0.6, 0.002≤m<0.02, 0.002≤n<0.02, 0.002≤w<0.02, m+n+w=0.02.

[0027] In one embodiment of the present invention, the nickel salt in the doped mixed salt solution includes any one or a combination of at least two of nickel chloride, nickel sulfate, or nickel nitrate. Typical but non-limiting combinations include a combination of nickel chloride and nickel sulfate, a combination of nickel chloride and nickel nitrate, a combination of nickel sulfate and nickel nitrate, or a combination of nickel chloride, nickel sulfate, and nickel nitrate.

[0028] The cobalt salt in the doped mixed salt solution includes any one or a combination of at least two of cobalt chloride, cobalt sulfate, or cobalt nitrate. Typical but non-limiting combinations include combinations of cobalt chloride and cobalt sulfate, cobalt chloride and cobalt nitrate, cobalt sulfate and cobalt nitrate, or cobalt chloride, cobalt sulfate, and cobalt nitrate.

[0029] The manganese salt in the doped mixed salt solution includes any one or a combination of at least two of manganese chloride, manganese sulfate, or manganese nitrate. Typical but non-limiting combinations include combinations of manganese chloride and manganese sulfate, manganese chloride and manganese nitrate, manganese sulfate and manganese nitrate, or manganese chloride, manganese sulfate, and manganese nitrate.

[0030] The magnesium salt in a mixed salt solution can be magnesium nitrate.

[0031] The titanium salt in the doped mixed salt solution can be any one or a combination of at least two of titanium sulfate, titanium tetrachloride, or tetrabutyl titanate. Typical but non-limiting combinations include combinations of titanium sulfate and titanium tetrachloride, combinations of titanium sulfate and tetrabutyl titanate, combinations of titanium tetrachloride and tetrabutyl titanate, or combinations of titanium sulfate, titanium tetrachloride, and tetrabutyl titanate.

[0032] The Y salt in the doped mixed salt solution can be yttrium nitrate and / or yttrium chloride.

[0033] The Zr salt in the doped mixed salt solution can be zirconium nitrate and / or zirconium sulfate.

[0034] In one embodiment of the present invention, the concentration of the doped mixed salt solution is 85 g / L to 115 g / L, for example, it can be 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L or 115 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0035] In one embodiment of the present invention, the temperature of the first coprecipitation reaction is 45°C to 65°C, for example, it can be 45°C, 50°C, 55°C, 60°C or 65°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] In one embodiment of the present invention, the pH value of the first coprecipitation reaction is 9 to 10, for example, it can be 9, 9.5 or 10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] In one embodiment of the present invention, during the first coprecipitation reaction, the concentration of the first complexing agent in the system is 5 g / L to 40 g / L, for example, it can be 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L or 40 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0038] In one embodiment of the present invention, the temperature of the second coprecipitation reaction is 45°C to 65°C, for example, it can be 45°C, 50°C, 55°C, 60°C or 65°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] In one embodiment of the present invention, the pH value of the second coprecipitation reaction is 9.5 to 10.5, for example, it can be 9.5, 10 or 10.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] In one embodiment of the present invention, during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 5 g / L to 40 g / L, for example, it can be 5 g / L, 10 g / L, 20 g / L, 30 g / L or 40 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] In one embodiment of the present invention, the median particle size of the lithium-rich nickel-cobalt-manganese precursor core is D501, and the median particle size of the doped core-shell precursor is D502.

[0042] D501 is 8μm~10μm, for example, it can be 8μm, 9μm or 10μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Furthermore, D502-D501 ranges from 0.5μm to 2μm, for example, it can be 0.5μm, 1μm, 1.5μm or 2μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] In one embodiment of the present invention, the lithium source includes lithium carbonate.

[0045] In one embodiment of the present invention, the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.35:1 to 1.5:1, for example, it can be 1.35:1, 1.4:1, 1.45:1 or 1.5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] In one embodiment of the present invention, the temperature of the first calcination is 850°C to 950°C, and the time is 10h to 14h.

[0047] The temperature for the first calcination is 850℃~950℃, for example, it can be 850℃, 880℃, 900℃, 920℃ or 950℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] The first calcination time is 10h to 14h, for example, it can be 10h, 11h, 12h, 13h or 14h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] In one embodiment of the present invention, the coating material includes any one or a combination of at least two of Al2O3, MoO3 or Nb2O5;

[0050] In one embodiment of the present invention, the coating material is 0.1wt% to 0.3wt% of the doped core-shell cathode material, for example, it can be 0.1wt%, 0.2wt% or 0.3wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] In one embodiment of the present invention, the second calcination temperature is 300℃~500℃ and the time is 3h~7h.

[0052] The second calcination temperature is 300℃~500℃, for example, it can be 300℃, 350℃, 400℃, 450℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] The second calcination time is 3h to 7h, for example, it can be 3h, 4h, 5h, 6h or 7h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes the following steps:

[0055] (1) A mixed salt solution of nickel, cobalt and manganese, a precipitant solution and a first complexing agent solution are introduced into the bottom liquid with a pH of 11 to 12 in parallel. The first coprecipitation reaction is carried out at a temperature of 45℃ to 65℃, a pH of 9 to 10 and a stirring speed of 300 rpm to 700 rpm to obtain a lithium-rich nickel, cobalt and manganese precursor core with a median particle size D501 of 8 μm to 10 μm.

[0056] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is x. a :y a :z a , where x a +y a +z a =1, z a ≥0.6; the concentration of the nickel-cobalt-manganese mixed salt solution is 85 g / L~115 g / L;

[0057] The precipitant solution is a sodium hydroxide solution and / or potassium hydroxide solution with a concentration of 28wt%~35wt%.

[0058] The first complexing agent is any one of ammonia, oxalic acid, citric acid, sodium tartrate, or EDTA; during the first coprecipitation reaction, the concentration of the first complexing agent in the system is 5 g / L to 40 g / L.

[0059] (2) Stop the flow of nickel-cobalt-manganese mixed salt solution and first complexing agent solution, and simultaneously start the flow of doped mixed salt solution and second complexing agent solution in parallel to carry out the second coprecipitation reaction at a temperature of 45℃~65℃, a pH value of 9.5~10.5 and a stirring speed of 300rpm~700rpm to obtain a doped core-shell precursor with a median particle size of D502;

[0060] Among them, D502-D501 are 0.5μm~2μm;

[0061] In the doped mixed salt solution, the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium is x. b :y b :z b :m:n:w, where x b +y b +z b =1, z b ≥0.6, 0.002≤m<0.02, 0.002≤n<0.02, 0.002≤w<0.02, m+n+w=0.02; the doped metal M includes Y and / or Zr; the concentration of the doped mixed salt solution is 85g / L~115g / L;

[0062] The second complexing agent in the second complexing agent solution includes ammonia water and EDTA in a mass ratio of 1:1 to 10:1, or includes oxalic acid and EDTA in a mass ratio of 1:1 to 10:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 5 g / L to 40 g / L;

[0063] (3) Mix the lithium source with the doped core-shell precursor obtained in step (2), and calcine the mixture to obtain the doped core-shell cathode material.

[0064] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.35:1 to 1.5:1;

[0065] The first calcination temperature is 850℃~950℃, and the time is 10h~14h;

[0066] (4) The coating material and the doped core-shell cathode material described in step (3) are mixed and calcined a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material;

[0067] The coating material includes any one or a combination of at least two of Al2O3, MoO3, or Nb2O5; the coating material is 0.1wt% to 0.3wt% of the doped core-shell cathode material.

[0068] The second calcination temperature is 300℃~500℃, and the time is 3h~7h.

[0069] In a second aspect, the present invention provides a composite modified lithium-rich manganese-based cathode material, wherein the composite modified lithium-rich manganese-based cathode material is prepared by the preparation method described in the first aspect.

[0070] Thirdly, the present invention provides a positive electrode, the positive electrode comprising a composite modified lithium-rich manganese-based positive electrode material prepared by the preparation method described in the first aspect, or comprising the composite modified lithium-rich manganese-based positive electrode material described in the second aspect.

[0071] 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.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] The preparation method provided by this invention ensures the uniformity of doping by using a mixed salt, and the doped metal ions can preferentially occupy the metal sites in the precursor lattice, hindering the transition metal ions (Mn) from being present. 2+ And / or Ni 2+ The migration channels of ) play a role in structural anchoring; the low-valence element Mg in the doped mixed salt solution 2+ With high-priced element Ti 4+ It can optimize the charge distribution within the crystal lattice, reduce the generation of oxygen vacancies, and maintain the long-term stability of the layered structure; the use of coating materials can alleviate interfacial stress, form a dual protection of doping and coating, and comprehensively improve the electrochemical performance and cycle stability of the material. Detailed Implementation

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0078] 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.

[0079] 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.

[0080] 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."

[0081] 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.

[0082] 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.

[0083] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0084] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0085] Example 1

[0086] This embodiment provides a method for preparing a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0087] (1) In a nitrogen atmosphere, a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution were introduced in parallel into a bottom liquid with a pH of 11. The first coprecipitation reaction was carried out at a temperature of 58℃, a pH of 9.5 and a stirring speed of 500rpm to obtain a lithium-rich nickel-cobalt-manganese precursor core with a median particle size D501 of 8.5μm.

[0088] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is 0.3:0.05:0.65; the concentration of the nickel-cobalt-manganese mixed salt solution is 100 g / L, and the metal salts therein are nickel sulfate, cobalt sulfate, and manganese sulfate.

[0089] The precipitant solution is a 32wt% sodium hydroxide solution;

[0090] During the first coprecipitation reaction, the concentration of the first complexing agent in the system is 10 g / L, and the first complexing agent is ammonia.

[0091] (2) In a nitrogen atmosphere, stop the flow of nickel-cobalt-manganese mixed salt solution and the first complexing agent solution, and simultaneously start the parallel flow of doped mixed salt solution and the second complexing agent solution to carry out the second coprecipitation reaction at a temperature of 58°C, a pH value of 10 and a stirring speed of 500 rpm to obtain a doped core-shell precursor with a median particle size D502 of 10 μm; wash three times with saturated sodium hydroxide solution and pure water respectively, filter and dry at 100°C;

[0092] In the doped mixed salt solution, the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium is 0.3:0.05:0.65:0.005:0.005:0.01; the doped metal M is Y; the concentration of the doped mixed salt solution is 100 g / L, and the metal salts therein include nickel sulfate, cobalt sulfate, manganese sulfate, yttrium nitrate, magnesium nitrate, and titanium sulfate.

[0093] The second complexing agent in the second complexing agent solution comprises ammonia and EDTA in a mass ratio of 5:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 12 g / L;

[0094] (3) Mix the lithium source and the doped core-shell precursor obtained in step (2), and calcine them in air to obtain the doped core-shell cathode material.

[0095] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.45:1;

[0096] The first calcination temperature is 900℃ and the time is 12h;

[0097] (4) The coating material and the doped core-shell cathode material described in step (3) are mixed and calcined a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material;

[0098] The coating material is Al2O3; the coating material is 0.2 wt% of the doped core-shell cathode material.

[0099] The second calcination temperature is 400℃ and the time is 5 hours.

[0100] Example 2

[0101] This embodiment provides a method for preparing a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0102] (1) In a nitrogen atmosphere, a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution were introduced concurrently into a bottom liquid with a pH of 12. The first coprecipitation reaction was carried out at a temperature of 58℃, a pH of 9.5 and a stirring speed of 500rpm to obtain a lithium-rich nickel-cobalt-manganese precursor core with a median particle size D501 of 9μm.

[0103] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is 0.35:0.05:0.60; the concentration of the nickel-cobalt-manganese mixed salt solution is 105 g / L, and the metal salts therein are nickel sulfate, cobalt sulfate, and manganese sulfate.

[0104] The precipitant solution is a 32wt% sodium hydroxide solution;

[0105] In the first coprecipitation reaction, the concentration of the first complexing agent in the system is 10 g / L, and the first complexing agent is oxalic acid;

[0106] (2) In a nitrogen atmosphere, stop the flow of nickel-cobalt-manganese mixed salt solution and the first complexing agent solution, and simultaneously start the parallel flow of doped mixed salt solution and the second complexing agent solution to carry out the second coprecipitation reaction at a temperature of 58°C, a pH value of 10 and a stirring speed of 500 rpm to obtain a doped core-shell precursor with a median particle size D502 of 10 μm; wash three times with saturated sodium hydroxide solution and pure water respectively, filter and dry at 100°C;

[0107] In the doped mixed salt solution, the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium is 0.35:0.05:0.60:0.01:0.005:0.005; the doped metal M is Zr; the concentration of the doped mixed salt solution is 100 g / L, and the metal salts therein include nickel sulfate, cobalt sulfate, manganese sulfate, zirconium sulfate, magnesium nitrate, and titanium sulfate.

[0108] The second complexing agent in the second complexing agent solution comprises oxalic acid and EDTA in a mass ratio of 10:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 11 g / L;

[0109] (3) Mix the lithium source and the doped core-shell precursor obtained in step (2), and calcine them in air to obtain the doped core-shell cathode material.

[0110] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.45:1;

[0111] The first calcination temperature was 920℃, and the time was 12 hours;

[0112] (4) The coating material and the doped core-shell cathode material described in step (3) are mixed and calcined a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material;

[0113] The coating material is MoO3; the coating material is 0.2 wt% of the doped core-shell cathode material.

[0114] The second calcination temperature is 400℃ and the time is 5 hours.

[0115] Example 3

[0116] This embodiment provides a method for preparing a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0117] (1) In a nitrogen atmosphere, a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution were introduced into the bottom liquid with a pH of 11 in parallel to carry out a first coprecipitation reaction at a temperature of 45℃, a pH of 9 and a stirring speed of 300rpm to obtain a lithium-rich nickel-cobalt-manganese precursor core with a median particle size D501 of 8μm.

[0118] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is 0.3:0.05:0.65; the concentration of the nickel-cobalt-manganese mixed salt solution is 85 g / L, and the metal salts therein are nickel sulfate, cobalt sulfate, and manganese sulfate.

[0119] The precipitant solution is a 28wt% sodium hydroxide solution;

[0120] During the first coprecipitation reaction, the concentration of the first complexing agent in the system is 5 g / L, and the first complexing agent is ammonia water;

[0121] (2) In a nitrogen atmosphere, the flow of nickel-cobalt-manganese mixed salt solution and the first complexing agent solution was stopped, and the flow of doped mixed salt solution and the second complexing agent solution was started simultaneously to carry out the second coprecipitation reaction at a temperature of 45°C, a pH of 9.5 and a stirring speed of 300 rpm, to obtain a doped core-shell precursor with a median particle size D502 of 8.5 μm; it was washed three times with saturated sodium hydroxide solution and pure water respectively, filtered and dried at 100°C;

[0122] In the doped mixed salt solution, the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium is 0.3:0.05:0.65:0.005:0.005:0.01; the doped metal M is Y; the concentration of the doped mixed salt solution is 100 g / L, and the metal salts therein include nickel sulfate, cobalt sulfate, manganese sulfate, yttrium nitrate, magnesium nitrate, and titanium sulfate.

[0123] The second complexing agent in the second complexing agent solution comprises ammonia and EDTA in a mass ratio of 1:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 5 g / L;

[0124] (3) Mix the lithium source and the doped core-shell precursor obtained in step (2), and calcine them in air to obtain the doped core-shell cathode material.

[0125] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.35:1;

[0126] The first calcination temperature was 850℃, and the time was 14 hours;

[0127] (4) The coating material and the doped core-shell cathode material described in step (3) are mixed and calcined a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material;

[0128] The coating material is Al2O3; the coating material is 0.1 wt% of the doped core-shell cathode material.

[0129] The second calcination temperature is 300℃ and the time is 7 hours.

[0130] Example 4

[0131] This embodiment provides a method for preparing a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0132] (1) In a nitrogen atmosphere, a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution are introduced in parallel into a bottom liquid with a pH of 11. A first coprecipitation reaction is carried out at a temperature of 65℃, a pH of 10 and a stirring speed of 700rpm to obtain a lithium-rich nickel-cobalt-manganese precursor core with a median particle size D501 of 10μm.

[0133] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is 0.3:0.05:0.65; the concentration of the nickel-cobalt-manganese mixed salt solution is 115 g / L, and the metal salts therein are nickel sulfate, cobalt sulfate, and manganese sulfate.

[0134] The precipitant solution is a 35wt% sodium hydroxide solution;

[0135] During the first coprecipitation reaction, the concentration of the first complexing agent in the system was 40 g / L, and the first complexing agent was ammonia.

[0136] (2) In a nitrogen atmosphere, stop the flow of nickel-cobalt-manganese mixed salt solution and the first complexing agent solution, and simultaneously start the parallel flow of doped mixed salt solution and the second complexing agent solution to carry out the second coprecipitation reaction at a temperature of 65℃, a pH value of 10.5 and a stirring speed of 700rpm, to obtain a doped core-shell precursor with a median particle size D502 of 12μm; wash three times with saturated sodium hydroxide solution and pure water respectively, filter and dry at 100℃;

[0137] In the doped mixed salt solution, the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium is 0.3:0.05:0.65:0.005:0.005:0.01; the doped metal M is Y; the concentration of the doped mixed salt solution is 115 g / L, and the metal salts therein include nickel sulfate, cobalt sulfate, manganese sulfate, yttrium nitrate, magnesium nitrate, and titanium sulfate.

[0138] The second complexing agent in the second complexing agent solution comprises ammonia and EDTA in a mass ratio of 10:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 40 g / L;

[0139] (3) Mix the lithium source and the doped core-shell precursor obtained in step (2), and calcine them in air to obtain the doped core-shell cathode material.

[0140] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.5:1;

[0141] The first calcination temperature was 950℃ and the time was 10 hours;

[0142] (4) The coating material and the doped core-shell cathode material described in step (3) are mixed and calcined a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material;

[0143] The coating material is Al2O3; the coating material is 0.3 wt% of the doped core-shell cathode material.

[0144] The second calcination temperature is 500℃ and the time is 3 hours.

[0145] Comparative Example 1

[0146] This comparative example provides a method for preparing a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0147] (1) In a nitrogen atmosphere, a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution were introduced in parallel into a bottom liquid with a pH of 11. The first coprecipitation reaction was carried out at a temperature of 58℃, a pH of 9.5 and a stirring speed of 500rpm to obtain a lithium-rich nickel-cobalt-manganese precursor core with a median particle size D501 of 8.5μm.

[0148] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is 0.3:0.05:0.65; the concentration of the nickel-cobalt-manganese mixed salt solution is 100 g / L, and the metal salts therein are nickel sulfate, cobalt sulfate, and manganese sulfate.

[0149] The precipitant solution is a 32wt% sodium hydroxide solution;

[0150] During the first coprecipitation reaction, the concentration of the first complexing agent in the system is 10 g / L, and the first complexing agent is ammonia.

[0151] (2) In a nitrogen atmosphere, stop the flow of the first complexing agent solution and start the flow of the second complexing agent solution at the same time to carry out the second coprecipitation reaction at a temperature of 58°C, a pH value of 10 and a stirring speed of 500 rpm to obtain a core-shell precursor with a median particle size D502 of 10 μm; wash three times with saturated sodium hydroxide solution and pure water respectively, filter and dry at 100°C;

[0152] The second complexing agent in the second complexing agent solution comprises ammonia and EDTA in a mass ratio of 5:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 12 g / L;

[0153] (3) Mix the lithium source and the core-shell precursor obtained in step (2), and calcine them in air to obtain the core-shell cathode material;

[0154] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the core-shell precursor is 1.45:1;

[0155] The first calcination temperature is 900℃ and the time is 12h;

[0156] (4) Mix the coating material with the core-shell cathode material described in step (3), and calcine the mixture a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material;

[0157] The coating material is Al2O3; the coating material is 0.2 wt% of the doped core-shell cathode material.

[0158] The second calcination temperature is 400℃ and the time is 5 hours.

[0159] Comparative Example 2

[0160] This comparative example provides a method for preparing a composite modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0161] (1) In a nitrogen atmosphere, a nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution were introduced in parallel into a bottom liquid with a pH of 11. The first coprecipitation reaction was carried out at a temperature of 58℃, a pH of 9.5 and a stirring speed of 500rpm to obtain a lithium-rich nickel-cobalt-manganese precursor core with a median particle size D501 of 8.5μm.

[0162] The molar ratio of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt solution is 0.3:0.05:0.65; the concentration of the nickel-cobalt-manganese mixed salt solution is 100 g / L, and the metal salts therein are nickel sulfate, cobalt sulfate, and manganese sulfate.

[0163] The precipitant solution is a 32wt% sodium hydroxide solution;

[0164] During the first coprecipitation reaction, the concentration of the first complexing agent in the system is 10 g / L, and the first complexing agent is ammonia.

[0165] (2) In a nitrogen atmosphere, stop the flow of nickel-cobalt-manganese mixed salt solution and the first complexing agent solution, and simultaneously start the parallel flow of doped mixed salt solution and the second complexing agent solution to carry out the second coprecipitation reaction at a temperature of 58°C, a pH value of 10 and a stirring speed of 500 rpm to obtain a doped core-shell precursor with a median particle size D502 of 10 μm; wash three times with saturated sodium hydroxide solution and pure water respectively, filter and dry at 100°C;

[0166] In the doped mixed salt solution, the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium is 0.3:0.05:0.65:0.005:0.005:0.01; the doped metal M is Y; the concentration of the doped mixed salt solution is 100 g / L, and the metal salts therein include nickel sulfate, cobalt sulfate, manganese sulfate, yttrium nitrate, magnesium nitrate, and titanium sulfate.

[0167] The second complexing agent in the second complexing agent solution comprises ammonia and EDTA in a mass ratio of 5:1; during the second coprecipitation reaction, the concentration of the second complexing agent in the system is 12 g / L;

[0168] (3) Mix the lithium source and the doped core-shell precursor obtained in step (2), and calcine them in air to obtain the doped core-shell cathode material, which is the composite modified lithium-rich manganese-based cathode material.

[0169] The lithium source is lithium carbonate; the molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.45:1;

[0170] The first calcination temperature was 900℃ and the time was 12h.

[0171] Performance Characterization

[0172] The above-obtained composite modified lithium-rich manganese-based cathode material was used to prepare lithium-ion coin cells. The specific capacity and cycle capacity retention of the obtained lithium-ion coin cells were tested using the Blue Electric CT2001A battery testing system in the voltage range of 2.0V to 4.8V. The test results are shown in Table 1.

[0173] The method for preparing a lithium-ion coin cell includes: weighing lithium-rich manganese-based cathode material with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) in a mass ratio of 8:1:1, dissolving them in N-methylpyrrolidone and mixing them thoroughly to obtain a slurry; then coating the slurry onto aluminum foil and drying it in a vacuum drying oven at 80°C for 8 hours; finally, pressing the aluminum foil into 1.13 cm diameter pieces. 2 The positive electrode is obtained by taking a circular piece of material; a lithium metal sheet is used as the counter electrode, and a polyethylene film (Celgard 2400) is used as the separator. The two are then assembled into a CR2032 button cell in an argon glove box.

[0174] Table 1

[0175] 0.1C discharge specific capacity (mAh / g) 0.2C discharge specific capacity (mAh / g) 0.5C discharge specific capacity (mAh / g) 1C discharge specific capacity (mAh / g) Capacity retention rate (%) after 100 cycles at 0.1C Example 1 276.8 267.2 254.9 236.6 97.6 Example 2 272.6 264.5 251.4 232.2 97.1 Example 3 268.9 258.3 240.5 222.8 96.2 Example 4 266.3 255.7 239.6 220.1 95.5 Comparative Example 1 230.8 217.5 201.8 188.5 77.6 Comparative Example 2 246.3 233.9 220.1 205.1 80.1

[0176] In summary, the preparation method provided by this invention ensures the uniformity of doping by using a mixed salt, and the doped metal ions can preferentially occupy the metal sites in the precursor lattice, hindering the transition metal ions (Mn) from being present. 2+ And / or Ni 2 +The migration channels of ) play a role in structural anchoring; the low-valence element Mg in the doped mixed salt solution 2+ With high-priced element Ti 4+ It can optimize the charge distribution within the crystal lattice, reduce the generation of oxygen vacancies, and maintain the long-term stability of the layered structure; the use of coating materials can alleviate interfacial stress, form a dual protection of doping and coating, and comprehensively improve the electrochemical performance and cycle stability of the material.

[0177] 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 composite modified lithium-rich manganese-based cathode material, characterized in that, The preparation method includes the following steps: (1) A nickel-cobalt-manganese mixed salt solution, a precipitant solution and a first complexing agent solution are introduced into the bottom liquid in parallel to carry out the first coprecipitation reaction to obtain the lithium-rich nickel-cobalt-manganese precursor core; The molar ratio of nickel, cobalt and manganese in the nickel-cobalt-manganese mixed salt solution is x a :y a :z a , wherein x a +y a +z a =1, z a ≥0.6; the concentration of the nickel-cobalt-manganese mixed salt solution is 85g / L~115g / L; (2) Stop the flow of nickel-cobalt-manganese mixed salt solution and first complexing agent solution, and simultaneously start the parallel flow of doped mixed salt solution and second complexing agent solution to carry out the second coprecipitation reaction and obtain doped core-shell precursor; The cations in the doped mixed salt solution include nickel, cobalt, manganese, magnesium, titanium, and a doped metal element M, wherein the doped metal M includes Y and / or Zr; the molar ratio of nickel, cobalt, manganese, doped metal M, magnesium, and titanium in the doped mixed salt solution is x. b :y b :z b :m:n:w, where x b +y b +z b =1, z b ≥0.6, 0.002≤m<0.02, 0.002≤n<0.02, 0.002≤w<0.02, m+n+w=0.02; the concentration of the doped mixed salt solution is 85g / L~115g / L; (3) Mix the lithium source with the doped core-shell precursor obtained in step (2), and calcine for the first time to obtain the doped core-shell cathode material; (4) Mix the coating material with the doped core-shell cathode material described in step (3), and calcine the mixture a second time to form a coating layer, thereby obtaining the composite modified lithium-rich manganese-based cathode material; The median particle size of the lithium-rich nickel-cobalt-manganese precursor core is D501, and the median particle size of the doped core-shell precursor is D502; then D501 is 8μm~10μm; and D502-D501 is 0.5μm~2μm.

2. The preparation method according to claim 1, characterized in that, The precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide; The concentration of the precipitant in the precipitant solution is 28wt%~35wt%.

3. The preparation method according to claim 1, characterized in that, The first complexing agent in the first complexing agent solution is any one of ammonia, oxalic acid, citric acid, sodium tartrate, or EDTA.

4. The preparation method according to claim 1, characterized in that, The second complexing agent in the second complexing agent solution includes any two of ammonia, citric acid, oxalic acid, tartaric acid, or EDTA, and includes EDTA.

5. The preparation method according to claim 4, characterized in that, The second complexing agent in the second complexing agent solution includes ammonia and EDTA in a mass ratio of 1:1 to 10:1, or includes oxalic acid and EDTA in a mass ratio of 1:1 to 10:

1.

6. The preparation method according to claim 1, characterized in that, The temperature of the first coprecipitation reaction is 45℃~65℃; The pH value of the first coprecipitation reaction is 9~10; During the first coprecipitation reaction, the concentration of the first complexing agent in the system is 5 g / L to 40 g / L.

7. The preparation method according to claim 1, characterized in that, The temperature for the second coprecipitation reaction is 45℃~65℃; The pH value of the second coprecipitation reaction is 9.5~10.5; During the second coprecipitation reaction, the concentration of the second complexing agent in the system is 5 g / L to 40 g / L.

8. The preparation method according to claim 1, characterized in that, The lithium source includes lithium carbonate.

9. The preparation method according to claim 1, characterized in that, The molar ratio of lithium in the lithium source to the doped core-shell precursor is 1.35:1 to 1.5:

1.

10. The preparation method according to claim 1, characterized in that, The first calcination temperature is 850℃~950℃, and the time is 10h~14h.

11. The preparation method according to claim 1, characterized in that, The coating material includes any one or a combination of at least two of Al2O3, MoO3, or Nb2O5.

12. The preparation method according to claim 1, characterized in that, The coating material is 0.1wt% to 0.3wt% of the doped core-shell cathode material.

13. The preparation method according to claim 1, characterized in that, The second calcination temperature is 300℃~500℃, and the time is 3h~7h.

14. A composite modified lithium-rich manganese-based cathode material, characterized in that, The composite modified lithium-rich manganese-based cathode material is prepared by the preparation method described in any one of claims 1 to 13.

15. A positive electrode, characterized in that, The cathode includes the composite modified lithium-rich manganese-based cathode material prepared by the preparation method according to any one of claims 1 to 13, or the composite modified lithium-rich manganese-based cathode material according to claim 14.