Carbonate precursor, preparation method and positive electrode material

Abstract

The application relates to a carbonate precursor, a preparation method and a positive electrode material. The carbonate precursor provided by the application is doped with Mg and Zr in a specific molar ratio 2+ , the radius of which is close to that of Li + , so that the Mg and Zr can occupy the lithium layer and stabilize the structure; Zr 4+ preferentially occupies the transition metal layer and inhibits lattice distortion. By doping Mg and Zr into the carbonate precursor in a specific molar ratio, the lithium-nickel mixing degree can be reduced, the phase transition in the cycle process can be inhibited, the decline of the rate performance caused by single-element doping can be avoided, and the electrochemical performance of the corresponding positive electrode material can be improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a carbonate precursor, its preparation method, and a cathode material. Background Technology

[0002] Lithium-ion batteries, as core energy storage devices in the new energy field, face critical bottlenecks in energy density and cycle stability that hinder the development of high-end applications such as electric vehicles and energy storage power stations. Lithium-rich layered oxides (LMRs), with their theoretical specific capacity exceeding 250 mAh / g, have become a core candidate system for next-generation high-energy-density battery cathode materials. The precursor, as the structural prototype of the cathode material, directly determines the electrochemical performance of the final product through its microstructure, packing density, and elemental uniformity.

[0003] Currently, there are two main precursor synthesis processes: carbonate precursors (CO3-LMR) and hydroxide precursors (OH-LRLO). Carbonate precursors, with their advantages of low raw material cost, simple synthesis process, and no need for stringent storage conditions, were widely used in the early industrialization of ternary cathode materials (NCM) and remain the primary precursor for LMR research. However, with the transition of NCM from carbonate to hydroxide precursors, research progress on carbonate precursors has fallen far behind, and existing carbonate precursors suffer from structural defects that limit their commercial application.

[0004] Li will form during the sintering process of the carbonate precursor. x The NiMn2O4 mesophase releases CO2, resulting in a final product composed of near-spherical primary particles with low packing density and high porosity. This microstructure intensifies interfacial reactions at the electrode, severely impacting cycle stability. Simultaneously, the low packing density leads to insufficient volumetric energy density, failing to meet the application requirements of high-end power batteries. In contrast, while hydroxide precursors can form high-density fibrous primary particles, their high raw material costs, stringent control of moisture and oxygen during synthesis, and demanding storage conditions significantly increase industrialization costs compared to carbonate routes.

[0005] Therefore, developing a precursor that combines the low-cost advantage of carbonate precursors with the high stability and high packing density of hydroxide precursors has become a breakthrough in solving the bottleneck of industrial application of lithium-rich manganese-based cathode materials. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a carbonate precursor, a preparation method and a cathode material. The carbonate precursor can reduce the lithium-nickel mixing degree by controlling the type and ratio of doping elements, suppress phase transition during cycling, avoid the rate performance degradation caused by single element doping, and improve the electrochemical performance of the corresponding cathode material.

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

[0008] In a first aspect, the present invention provides a carbonate precursor, wherein the chemical formula of the carbonate precursor is Ni. x Co y Mn (1-x-y-α-β) Mg α Zr β CO3, wherein x is 0.15~0.25, y is 0.15~0.25, α is 0.005~0.02, x+y+α+β<1, and the molar ratio of Mg to Zr is 3:1~5:1.

[0009] Mg 2+ (ionic radius 0.072 nm) and Li + With a radius close to (0.076nm), Zr can occupy a stable lithium layer structure; 4+ (0.072nm) preferentially occupies the transition metal layer, suppressing lattice distortion; when the two are doped in a molar ratio of 3:1 to 5:1, it can reduce the lithium-nickel mixing degree and suppress the phase transition during cycling, avoiding the rate performance degradation caused by single doping. Therefore, by doping with Mg and Zr in a specific molar ratio, this invention can reduce the lithium-nickel mixing degree, suppress the phase transition during cycling, avoid the rate performance degradation caused by single element doping, and also improve the electrochemical performance of the corresponding cathode material.

[0010] Secondly, the present invention provides a method for preparing a carbonate precursor, the method comprising the following steps:

[0011] A metal salt solution and a composite precipitant solution are mixed in parallel in the base liquid and co-precipitated. The resulting slurry is then subjected to a first aging and a second aging. After solid-liquid separation, the slurry is washed and dried to obtain the carbonate precursor described in the first aspect.

[0012] The temperature for the first aging process is 45℃~55℃;

[0013] The second aging temperature is 65℃~75℃.

[0014] The preparation method provided by the present invention, through sequential first aging and second aging, can promote secondary aggregation between particles, reduce internal porosity, avoid hard agglomeration of particles caused by high-temperature aging, and ensure the fluidity of the precursor and the uniformity of subsequent sintering.

[0015] In some embodiments, the first aging time is 3 to 5 hours.

[0016] In some embodiments, the second aging time is 1.5h to 2.5h.

[0017] In some embodiments, the composite precipitant solution comprises a first precipitant solution and a second precipitant solution;

[0018] The first precipitant in the first precipitant solution is sodium carbonate;

[0019] The second precipitant in the second precipitant solution is ammonium bicarbonate.

[0020] In the composite precipitant solution used in this invention, sodium carbonate can provide the CO3 required for rapid nucleation. 2- Ammonium bicarbonate can slowly release CO3. 2- It also regulates the particle growth rate, causing the primary particles to transform from a near-spherical shape into a fibrous aggregate structure, thereby increasing the packing density.

[0021] In some embodiments, the volume ratio of the first precipitant solution to the second precipitant solution is 3:1 to 5:1.

[0022] When the amount of the first precipitant solution is relatively small, the nucleation efficiency will decrease; when the amount of the first precipitant solution is relatively large, the primary particles will remain spherical, which is not conducive to increasing the packing density.

[0023] In some embodiments, the concentration of the first precipitant solution is 1.2 mol / L to 1.8 mol / L.

[0024] In some embodiments, the concentration of the second precipitant solution is 0.5 mol / L to 0.8 mol / L.

[0025] In some embodiments, the total concentration of metal ions in the metal salt solution is 1 mol / L to 1.5 mol / L.

[0026] In some embodiments, the metal salts in the metal salt solution include nickel salts, cobalt salts, manganese salts, magnesium salts, and zirconium salts.

[0027] In some embodiments, the temperature of the coprecipitation reaction is 45°C to 55°C.

[0028] In some embodiments, the pH value of the coprecipitation reaction is 8.5 to 9.5.

[0029] In some embodiments, the stirring speed of the coprecipitation reaction is 600 rpm to 800 rpm;

[0030] In some embodiments, the flow rate of the metal salt solution during the coprecipitation reaction is 5 mL / min to 10 mL / min.

[0031] In some embodiments, the median particle size at the endpoint of the coprecipitation reaction is 8 μm to 10 μm.

[0032] In some embodiments, the base liquid consists of water, sodium carbonate, and ammonia.

[0033] In some embodiments, the temperature of the base liquid is 45°C to 55°C;

[0034] In some embodiments, the pH of the substrate solution is 8.5 to 9.5;

[0035] In some embodiments, the ammonia concentration of the substrate is 4 g / L to 10 g / L.

[0036] In some embodiments, the drying includes vacuum drying at a temperature of 100°C to 110°C.

[0037] Thirdly, the present invention provides a positive electrode material, which is prepared from a carbonate precursor; the carbonate precursor is the carbonate precursor described in the first aspect, or the carbonate precursor prepared by the preparation method described in the second aspect.

[0038] 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.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) Mg 2+ (ionic radius 0.072 nm) and Li + With a radius close to (0.076nm), Zr can occupy a stable lithium layer structure; 4+ (0.072nm) preferentially occupies the transition metal layer, suppressing lattice distortion; when the two are doped in a molar ratio of 3:1 to 5:1, it can reduce the lithium-nickel mixing degree and suppress the phase transition during cycling, avoiding the rate performance decrease caused by single doping. Therefore, this invention can reduce the lithium-nickel mixing degree and suppress the phase transition during cycling by doping with Mg and Zr in a specific molar ratio, avoiding the rate performance decrease caused by single element doping, and also improving the electrochemical performance of the corresponding cathode material.

[0041] (2) The preparation method provided by the present invention can promote secondary aggregation between particles, reduce internal pores, avoid hard agglomeration of particles caused by high temperature aging, and ensure the fluidity of the precursor and the uniformity of subsequent sintering by performing the first aging and the second aging in sequence. Detailed Implementation

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0046] 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.

[0047] 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.

[0048] 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."

[0049] 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.

[0050] 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.

[0051] The primary particles of the carbonate precursor prepared by existing technology are nearly spherical with a bulk density of only 1.2 g / cm³. 3 ~1.5g / cm 3 The high porosity (25%–30%) of carbonate precursors leads to insufficient electrode compaction density and a volumetric energy density 15%–20% lower than that of hydroxide precursors, failing to meet the space utilization requirements of power batteries. The high porosity also results in an excessively large contact area between the electrode and electrolyte, exacerbating interfacial side reactions. In existing carbonate precursor preparation techniques, large nucleation particle sizes, rapid growth rates, and difficulty in control lead to uneven particle size distribution and poor flowability, affecting the uniformity of subsequent lithium mixing and sintering, and consequently causing fluctuations in battery performance consistency. Using a single carbonate precipitant easily introduces impurities, which form inert phases during cycling, reducing ionic conductivity and further deteriorating electrochemical performance. While calcium doping and single precipitant optimization can improve some properties of carbonate precursors, they cannot fundamentally resolve the core contradiction between packing density and cycle stability. For example, calcium-doped carbonate precursors can improve tap density, but the improvement in cycle stability is limited, and the difficulty in controlling the doping amount leads to a decrease in rate performance.

[0052] One embodiment of the present invention provides a carbonate precursor, wherein the chemical formula of the carbonate precursor is Ni. x Co y Mn (1-x-y-α-β) Mg α Zr β CO3, wherein x is 0.15~0.25, y is 0.15~0.25, α is 0.005~0.02, x+y+α+β<1, and the molar ratio of Mg to Zr is 3:1~5:1.

[0053] Mg 2+ (ionic radius 0.072 nm) and Li + With a radius close to (0.076nm), Zr can occupy a stable lithium layer structure; 4+ (0.072nm) preferentially occupies the transition metal layer, suppressing lattice distortion; when the two are doped in a molar ratio of 3:1 to 5:1, it can reduce the lithium-nickel mixing degree and suppress the phase transition during cycling, avoiding the rate performance degradation caused by single doping. Therefore, by doping with Mg and Zr in a specific molar ratio, this invention can reduce the lithium-nickel mixing degree, suppress the phase transition during cycling, avoid the rate performance degradation caused by single element doping, and also improve the electrochemical performance of the corresponding cathode material.

[0054] In this invention, the molar ratio of Mg to Zr is 3:1 to 5:1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. When the molar ratio of Mg to Zr is too low, Mg can enter the stable lithium layer structure. 2+ Limited capacity makes it impossible to effectively reduce lithium-nickel mixing and maintain the orderliness of the layered structure, while excessive Zr... 4+ This can easily lead to local lattice distortion and even the formation of electrochemically inert impurities, reducing the active sites and reversible specific capacity of the material, hindering lithium-ion diffusion and transport, and exacerbating side reactions at the electrode interface, ultimately resulting in a simultaneous deterioration of the material's rate performance and cycle stability. When the molar ratio of Mg to Zr is too high, Zr cannot be fully utilized. 4+ The lattice pinning and support of the transition metal layer makes it difficult to effectively suppress lattice distortion and irreversible phase transformation during charge-discharge cycling, easily leading to structural collapse and rapid capacity decay during cycling. Simultaneously, excessive Mg... 2+ It will partially crowd out the active sites of the transition metal layer, which will not only reduce the discharge specific capacity of the material, but also increase the lithium ion diffusion and migration barrier, causing a decrease in rate performance, and cannot avoid the performance shortcomings caused by excessive doping of a single element.

[0055] An embodiment of the present invention provides a method for preparing a carbonate precursor, the method comprising the following steps:

[0056] A metal salt solution and a composite precipitant solution are mixed in parallel in the base liquid and co-precipitated. The resulting slurry is then subjected to a first aging and a second aging. After solid-liquid separation, the slurry is washed and dried to obtain the carbonate precursor of the present invention.

[0057] The temperature of the first aging process is 45℃~55℃, for example, it can be 45℃, 48℃, 50℃, 52℃, 54℃ or 55℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] The second aging temperature is 65℃~75℃, for example, it can be 65℃, 68℃, 70℃, 72℃ or 75℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] The preparation method provided by the present invention, through sequential first aging and second aging, can promote secondary aggregation between particles, reduce internal porosity, avoid hard agglomeration of particles caused by high-temperature aging, and ensure the fluidity of the precursor and the uniformity of subsequent sintering.

[0060] When the first aging temperature is too low, the crystallization kinetics of the primary particles generated by co-precipitation are hindered, resulting in disordered lattice arrangement, low crystallinity, and a significant slowdown in the secondary orderly aggregation process of particles. It is difficult to form secondary spherical particles with regular morphology and uniform particle size, and problems such as fine powder enrichment and large particle size range are prone to occur. This directly leads to a wide particle size distribution of the precursor (high CV value) and poor elemental uniformity. At the same time, the particles are loosely packed and the tap density is low. When the first aging temperature is too high, the nucleation and growth rate of particles are out of control, and non-uniform agglomeration is prone to occur. On the one hand, a large amount of free fine powder is generated, which destroys the uniformity of particle size. On the other hand, some particles are prematurely over-densified, which squeezes out the gradient control space of the second stage of high-temperature aging and makes it impossible to achieve subsequent densification optimization. Instead, it exacerbates the problems of uneven particle size and high porosity.

[0061] When the second aging temperature is too low, the driving force for recrystallization inside the particles is insufficient, the gaps between primary particles cannot be effectively filled, the internal pores are difficult to eliminate, the densification process is insufficient, the precursor tap density is low and the porosity is high, and the subsequent high-temperature sintering is prone to retaining a large number of micropores, which deteriorates the compaction density and interface stability of the cathode material. When the second aging temperature is too high, the particle interface energy decreases sharply, which easily leads to grain boundary fusion and abnormal growth, forming hard agglomerates. This not only significantly degrades the flowability of the precursor powder (larger angle of repose), but also hinders the uniform diffusion of lithium salts in the subsequent lithium mixing process, causing uneven lithium distribution and element segregation, ultimately resulting in a low initial coulombic efficiency of the cathode material and a significant decrease in cycle stability and rate performance.

[0062] In some embodiments, the first aging time is 3h to 5h, for example, it can be 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In some embodiments, the second aging time is 1.5h to 2.5h, for example, it can be 1.5h, 1.8h, 2h, 2.1h, 2.4h or 2.5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the composite precipitant solution comprises a first precipitant solution and a second precipitant solution;

[0065] The first precipitant in the first precipitant solution is sodium carbonate;

[0066] The second precipitant in the second precipitant solution is ammonium bicarbonate.

[0067] In the composite precipitant solution used in this invention, sodium carbonate can provide the CO3 required for rapid nucleation. 2- Ammonium bicarbonate can slowly release CO3. 2-It also regulates the particle growth rate, causing the primary particles to transform from a near-spherical shape into a fibrous aggregate structure, thereby increasing the packing density.

[0068] In some embodiments, the volume ratio of the first precipitant solution to the second precipitant solution is 3:1 to 5:1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] When the amount of the first precipitant solution is relatively small, the nucleation efficiency will decrease; when the amount of the first precipitant solution is relatively large, the primary particles will remain spherical, which is not conducive to increasing the packing density.

[0070] In some embodiments, the concentration of the first precipitant solution is 1.2 mol / L to 1.8 mol / L, for example, it can be 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L or 1.8 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the concentration of the second precipitant solution is 0.5 mol / L to 0.8 mol / L, for example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L or 0.8 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the total concentration of metal ions in the metal salt solution is 1 mol / L to 1.5 mol / L, for example, it can be 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the metal salts in the metal salt solution include nickel salts, cobalt salts, manganese salts, magnesium salts, and zirconium salts.

[0074] For example, the nickel salt can be any one or a combination of at least two of nickel chloride, nickel sulfate, or nickel nitrate. Typical but non-limiting combinations include combinations of nickel chloride and nickel sulfate, nickel chloride and nickel nitrate, nickel nitrate and nickel sulfate, or combinations of nickel chloride, nickel sulfate, and nickel nitrate.

[0075] For example, the cobalt salt can be 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 nitrate and cobalt sulfate, or cobalt chloride, cobalt sulfate, and cobalt nitrate.

[0076] For example, the manganese salt can be 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 nitrate and manganese sulfate, or manganese chloride, manganese sulfate, and manganese nitrate.

[0077] For example, the magnesium salt can be any one or a combination of at least two of magnesium chloride, magnesium sulfate, or magnesium nitrate. Typical but non-limiting combinations include combinations of magnesium chloride and magnesium sulfate, magnesium chloride and magnesium nitrate, magnesium nitrate and magnesium sulfate, or magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0078] For example, the zirconium salt can be any one or a combination of at least two of zirconium oxychloride, zirconium sulfate, or zirconium nitrate. Typical but non-limiting combinations include combinations of zirconium oxychloride and zirconium sulfate, combinations of zirconium oxychloride and zirconium nitrate, combinations of zirconium nitrate and zirconium sulfate, or combinations of zirconium oxychloride, zirconium sulfate, and zirconium nitrate.

[0079] In some embodiments, the temperature of the coprecipitation reaction is 45°C to 55°C, for example, 45°C, 46°C, 48°C, 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, the pH value of the coprecipitation reaction is 8.5 to 9.5, for example, it can be 8.5, 9 or 9.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0081] In some embodiments, the stirring speed of the coprecipitation reaction is 600 rpm to 800 rpm, for example, 600 rpm, 650 rpm, 700 rpm, 750 rpm or 800 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, during the coprecipitation reaction, the flow rate of the metal salt solution is 5 mL / min to 10 mL / min, for example, it can be 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min or 10 mL / min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the median particle size at the endpoint of the coprecipitation reaction is 8 μm to 10 μm, for example, it can be 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0084] In some embodiments, the base liquid consists of water, sodium carbonate, and ammonia.

[0085] In some embodiments, the temperature of the base liquid is 45°C to 55°C, for example, it can be 45°C, 46°C, 48°C, 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0086] In some embodiments, the pH value of the substrate is 8.5 to 9.5, for example, it can be 8.5, 9 or 9.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0087] In some embodiments, the ammonia concentration of the base liquid is 4 g / L to 10 g / L, for example, it can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0088] In some embodiments, the drying includes vacuum drying at a temperature of 100°C to 110°C.

[0089] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes the following steps:

[0090] S1, mix water, sodium carbonate and ammonia to obtain the base solution;

[0091] The temperature of the base solution is 45℃~55℃, the pH value is 8.5~9.5, and the ammonia concentration is 4g / L~10g / L;

[0092] S2. The metal salt solution and the composite precipitant solution are mixed in parallel in the bottom liquid and co-precipitated to obtain a slurry.

[0093] The metal salts in the metal salt solution include nickel salts, cobalt salts, manganese salts, magnesium salts, and zirconium salts, and the total concentration of metal ions is 1 mol / L to 1.5 mol / L;

[0094] The composite precipitant solution comprises a first precipitant solution and a second precipitant solution in a volume ratio of 3:1 to 5:1; the first precipitant solution is a sodium carbonate solution with a concentration of 1.2 mol / L to 1.8 mol / L; and the second precipitant solution is an ammonium bicarbonate solution with a concentration of 0.5 mol / L to 0.8 mol / L.

[0095] During the coprecipitation reaction, the flow rate of the metal salt solution is 5 mL / min to 10 mL / min;

[0096] The coprecipitation reaction was carried out at a temperature of 45℃~55℃, a pH value of 8.5~9.5, a stirring speed of 600rpm~800rpm, and a median particle size at the endpoint of 8μm~10μm.

[0097] S3. The obtained slurry is subjected to first aging and second aging in sequence. After solid-liquid separation, it is washed (washed with deionized water until the conductivity of the filtrate is <50μS / cm), vacuum dried at 100℃~110℃, and demagnetized to obtain the carbonate precursor.

[0098] The first aging process is carried out at a temperature of 45℃~55℃ for 3h~5h.

[0099] The second aging process takes place at a temperature of 65℃~75℃ for 1.5h~2.5h.

[0100] This invention provides a cathode material, which is prepared from a carbonate precursor;

[0101] The carbonate precursor is the carbonate precursor described in the first aspect, or the carbonate precursor prepared by the preparation method described in the second aspect.

[0102] For example, the preparation method of the cathode material includes mixing a lithium source and a carbonate precursor, sintering at 700℃~800℃ for 8h~12h to obtain the cathode material.

[0103] In the following specific implementation, the tap density of the carbonate precursor was measured according to the standard GB / T 5162-2006 "Determination of Tap Density of Metal Powders";

[0104] The porosity of the carbonate precursor was measured by mercury intrusion porosimetry (refer to GB / T 21650.1-2008 "Mercury intrusion porosimetry and gas adsorption method for determination of pore size distribution and porosity of solid materials - Part 1: Mercury intrusion porosimetry").

[0105] The CV of the carbonate precursor was measured using a laser particle size analyzer, where CV = [(D 90 -D 10 ) / D 50 ×100%;

[0106] The angle of repose was measured using the fixed funnel method (refer to GB / T 11986-2022 "Determination of Angle of Repose of Surfactant Powders and Particles").

[0107] Electrochemical performance: Assemble CR2032 button half-cells with a voltage range of 2.0V~4.8V, test the coulombic efficiency of the first charge-discharge at 0.1C, the discharge capacity at 5C rate, and perform 350 cycles of 1C constant current charge-discharge at 55℃, and calculate the cycle capacity retention rate.

[0108] Example 1

[0109] This embodiment provides a method for preparing a carbonate precursor, including the following steps:

[0110] S1, mix water, sodium carbonate and ammonia to obtain the base solution;

[0111] The temperature of the base solution is 50℃, the pH value is 9, and the ammonia concentration is 6g / L;

[0112] S2. The metal salt solution and the composite precipitant solution are mixed in parallel in the bottom liquid and co-precipitated to obtain a slurry.

[0113] The metal salts in the metal salt solution include nickel sulfate, cobalt sulfate, manganese sulfate, magnesium sulfate, and zirconium sulfate, and the total concentration of metal ions is 1.2 mol / L.

[0114] The composite precipitant solution comprises a first precipitant solution and a second precipitant solution in a volume ratio of 4:1; the first precipitant solution is a sodium carbonate solution with a concentration of 1.5 mol / L; and the second precipitant solution is an ammonium bicarbonate solution with a concentration of 0.6 mol / L.

[0115] During the coprecipitation reaction, the flow rate of the metal salt solution is 8 mL / min;

[0116] The coprecipitation reaction was carried out at a temperature of 50°C, a pH of 9, a stirring speed of 700 rpm, and a median particle size of 9 μm at the endpoint.

[0117] S3. The obtained slurry is subjected to first aging and second aging in sequence. After solid-liquid separation, it is washed (washed with deionized water until the conductivity of the filtrate is <50μS / cm), vacuum dried at 105℃ for 12h, and demagnetized to obtain the carbonate precursor.

[0118] The first aging process was carried out at a temperature of 50°C for 4 hours.

[0119] The second aging process was carried out at a temperature of 70°C for 2 hours.

[0120] The chemical formula of the carbonate precursor obtained in this embodiment is Ni. 0.2 Co 0.2 Mn 0.58 Mg 0.016 Zr 0.004 CO3, wherein the molar ratio of Mg to Zr is 4:1.

[0121] Example 2

[0122] This embodiment provides a method for preparing a carbonate precursor, including the following steps:

[0123] S1, mix water, sodium carbonate and ammonia to obtain the base solution;

[0124] The temperature of the base solution was 45°C, the pH value was 8.5, and the ammonia concentration was 4 g / L.

[0125] S2. The metal salt solution and the composite precipitant solution are mixed in parallel in the bottom liquid and co-precipitated to obtain a slurry.

[0126] The metal salts in the metal salt solution include nickel sulfate, cobalt sulfate, manganese sulfate, magnesium sulfate, and zirconium sulfate, and the total concentration of metal ions is 1 mol / L.

[0127] The composite precipitant solution comprises a first precipitant solution and a second precipitant solution in a volume ratio of 3:1; the first precipitant solution is a sodium carbonate solution with a concentration of 1.2 mol / L; and the second precipitant solution is an ammonium bicarbonate solution with a concentration of 0.5 mol / L.

[0128] During the coprecipitation reaction, the flow rate of the metal salt solution is 5 mL / min;

[0129] The coprecipitation reaction was carried out at a temperature of 45°C, a pH of 8.5, a stirring speed of 600 rpm, and a median particle size of 8 μm at the endpoint.

[0130] S3. The obtained slurry is subjected to first aging and second aging in sequence. After solid-liquid separation, it is washed (washed with deionized water until the conductivity of the filtrate is <50μS / cm), vacuum dried at 100℃ for 12h, and demagnetized to obtain the carbonate precursor.

[0131] The first aging process was carried out at a temperature of 45°C for 5 hours.

[0132] The second aging process was carried out at a temperature of 65°C for 2.5 hours.

[0133] The chemical formula of the carbonate precursor obtained in this embodiment is Ni. 0.2 Co 0.2 Mn 0.592 Mg 0.006 Zr 0.002 CO3, wherein the molar ratio of Mg to Zr is 3:1.

[0134] Example 3

[0135] This embodiment provides a method for preparing a carbonate precursor, including the following steps:

[0136] S1, mix water, sodium carbonate and ammonia to obtain the base solution;

[0137] The temperature of the base solution is 55℃, the pH value is 9.5, and the ammonia concentration is 10g / L;

[0138] S2. The metal salt solution and the composite precipitant solution are mixed in parallel in the bottom liquid and co-precipitated to obtain a slurry.

[0139] The metal salts in the metal salt solution include nickel sulfate, cobalt sulfate, manganese sulfate, magnesium sulfate, and zirconium sulfate, and the total concentration of metal ions is 1.5 mol / L.

[0140] The composite precipitant solution comprises a first precipitant solution and a second precipitant solution in a volume ratio of 5:1; the first precipitant solution is a sodium carbonate solution with a concentration of 1.8 mol / L; and the second precipitant solution is an ammonium bicarbonate solution with a concentration of 0.8 mol / L.

[0141] During the coprecipitation reaction, the flow rate of the metal salt solution is 10 mL / min;

[0142] The coprecipitation reaction was carried out at a temperature of 55°C, a pH of 9.5, a stirring speed of 800 rpm, and a median particle size of 10 μm at the endpoint.

[0143] S3. The obtained slurry is subjected to first aging and second aging in sequence. After solid-liquid separation, it is washed (washed with deionized water until the conductivity of the filtrate is <50μS / cm), vacuum dried at 110℃ for 12h, and demagnetized to obtain the carbonate precursor.

[0144] The first aging process was carried out at a temperature of 55°C for 3 hours.

[0145] The second aging process was carried out at a temperature of 75°C for 1.5 hours.

[0146] The chemical formula of the carbonate precursor obtained in this embodiment is Ni. 0.2 Co 0.2 Mn 0.576 Mg 0.02 Zr 0.004 CO3, wherein the molar ratio of Mg to Zr is 5:1.

[0147] Comparative Examples 1 to 2

[0148] In Comparative Examples 1 and 2, except for changing the amount of Mg salt and Zr salt in the metal salt solution, keeping the total molar amount of Mg and Zr constant, but changing the molar ratio of Mg and Zr as shown in Table 1, everything else was the same as in Example 1.

[0149] Table 1

[0150]

[0151] Comparative Examples 3 to 8

[0152] In Comparative Examples 3 to 8, except for the changes in the conditions for the first and second aging processes as shown in Table 2, the rest were the same as in Example 1.

[0153] Table 2

[0154]

[0155] Examples 4-5 and Comparative Examples 9-10

[0156] In Examples 4-5 and Comparative Examples 9-10, except for the change in the volume ratio of the first precipitant solution to the second precipitant solution as shown in Table 3, everything else was the same as in Example 1.

[0157] Table 3

[0158]

[0159] The carbonate precursors prepared in the above examples and comparative examples were mixed with lithium hydroxide and sintered at 750°C for 10 hours to obtain the cathode material. The obtained positive electrode material, conductive carbon black SP, and polyvinylidene fluoride PVDF were mixed in a mass ratio of 90:5:5, with N-methylpyrrolidone as the solvent. The mixture was stirred into a slurry, which was then uniformly coated onto aluminum foil using a doctor blade with a 100 μm coating gap. After coating, the foil was first dried by blowing air, then rolled and cut into circular electrode sheets. After vacuum drying at 120°C, the electrode sheets were weighed to obtain the positive electrode sheet of the button half-cell. The negative electrode was a lithium metal sheet, the separator was a PP microporous membrane, and the electrolyte was a basic lithium battery electrolyte. The positive electrode sheet, lithium metal sheet, separator, and electrolyte were assembled to obtain a CR2032 button cell. The coulombic efficiency of the first charge-discharge at 0.1C and the discharge performance at 5C rate were tested within a voltage range of 2V~4.8V at room temperature. The cycle capacity retention rate was tested by constant current charge-discharge at 1C rate for 350 cycles at a constant temperature of 55°C. The results are shown in Table 4.

[0160] Table 4

[0161]

[0162] As can be seen from Examples 1 to 3 in Tables 1 and 4, by controlling the molar ratio of Mg to Zr in the range of 3:1 to 5:1, the present invention can prepare carbonate precursors with high tap density, low porosity, uniform particle size distribution and good flowability. The corresponding cathode materials prepared have higher initial coulombic efficiency, excellent rate performance and cycle stability, and achieve a comprehensive improvement in electrochemical performance.

[0163] A comparison of Comparative Examples 1 and 2 with Example 1 shows that when the molar ratio of Mg to Zr deviates from the defined range of 3:1 to 5:1, it is impossible to simultaneously achieve the desired physicochemical properties of the precursor and the electrochemical performance of the cathode material. In Comparative Example 1, the Mg content is too low and the Zr content is too high, which fails to adequately occupy the lithium layer to stabilize the crystal structure, resulting in increased lithium-nickel mixing and obstruction of lithium-ion transport channels, leading to a significant decrease in rate performance and initial coulombic efficiency. In Comparative Example 2, the Mg content is too high and the Zr content is too low, which fails to adequately occupy the transition metal layer to suppress lattice distortion and phase transitions during cycling, increasing the risk of structural collapse during long-term cycling and significantly reducing the cycle capacity retention rate. Furthermore, excessive Mg doping also reduces active sites, resulting in a decrease in discharge capacity.

[0164] A comparison of Comparative Examples 3 and 4 with Example 1 shows that the temperature of the first aging process must be strictly controlled within a limited range to achieve controllable growth of the precursor particles. In Comparative Example 3, the first aging temperature was too low, resulting in insufficient nucleation and growth momentum of the particles, which failed to form dense secondary particles. This led to high precursor porosity, low tap density, and large particle size distribution dispersion (high CV value), ultimately causing insufficient lithium-ion transport efficiency of the cathode material and a significant decrease in rate and cycle performance. In Comparative Example 4, the first aging temperature was too high, resulting in uncontrolled particle growth rate and premature hard agglomeration. This led to poor precursor fluidity (increased angle of repose), insufficient uniformity in subsequent sintering, increased interfacial impedance, and a significant degradation in electrochemical performance.

[0165] A comparison of Comparative Examples 5 and 6 with Example 1 shows that the temperature of the second aging process must be strictly controlled within a limited range to achieve secondary aggregation and densification of the particles. In Comparative Example 5, the second aging temperature was too low, which could not effectively promote secondary aggregation between particles. The pores inside the precursor could not be effectively filled, resulting in low tap density, high porosity, and an inability to form a stable secondary particle structure. In Comparative Example 6, the second aging temperature was too high, leading to excessive particle growth and severe hard agglomeration. The uniformity of particle size distribution deteriorated, the fluidity of the precursor decreased significantly, and local overburning was likely to occur during subsequent sintering, resulting in deterioration of the electrochemical performance of the cathode material.

[0166] A comparison of Comparative Examples 7 and 8 with Example 1 shows that only a two-step aging process, involving sequential first and second aging, can balance the density and dispersibility of the precursor. Comparative Example 7, lacking a first aging, suffers from uneven nucleation and initial growth of particles, making it prone to uneven nucleation and significant particle size variations during high-temperature aging, resulting in a significantly increased CV value. Comparative Example 8, without a second aging, fails to achieve secondary particle aggregation and densification, resulting in high precursor porosity, low tap density, and a loose secondary particle structure. This leads to structural breakage during subsequent sintering and cycling, causing a substantial decrease in cycle stability.

[0167] As can be seen from Examples 1, 4 and 5 in Tables 3 and 4, by controlling the volume ratio of the first precipitant sodium carbonate solution to the second precipitant ammonium bicarbonate solution, the present invention can prepare a carbonate precursor with high tap density, low porosity, uniform particle size distribution and good flowability. The corresponding cathode material prepared has better first charge-discharge efficiency, rate performance and cycle stability.

[0168] A comparison of Comparative Examples 9 and 10 with Example 1 shows that only the synergistic effect of the composite precipitant composed of sodium carbonate and ammonium bicarbonate can achieve controllable growth and performance optimization of precursor particles. Comparative Example 9 used only the first precipitant, sodium carbonate solution, resulting in an excessively fast precipitation reaction rate, uncontrolled particle nucleation, and the formation of numerous fine particles and agglomerates. This led to extremely low tap density, significantly increased porosity and angle of repose in the precursor, and extremely poor particle size uniformity. Comparative Example 10 used only the second precipitant, ammonium bicarbonate solution, resulting in insufficient precipitation reaction kinetics, slow particle growth, and the inability to form dense secondary particles. Consequently, the physicochemical properties of the precursor and the electrochemical performance of the corresponding cathode material both deteriorated significantly.

[0169] In summary, in the carbonate precursor provided by this invention, Mg 2+ (ionic radius 0.072 nm) and Li + With a radius close to (0.076nm), Zr can occupy a stable lithium layer structure; 4+ (0.072nm) preferentially occupies the transition metal layer, suppressing lattice distortion; when the two are doped in a molar ratio of 3:1 to 5:1, it can reduce the lithium-nickel mixing degree and suppress the phase transition during cycling, avoiding the rate performance degradation caused by single doping. Therefore, the present invention can reduce the lithium-nickel mixing degree and suppress the phase transition during cycling by doping with Mg and Zr in a specific molar ratio, avoiding the rate performance degradation caused by single element doping, and also improving the electrochemical performance of the corresponding cathode material; the preparation method provided by the present invention can promote secondary aggregation between particles by performing a first aging and a second aging in sequence, reduce internal porosity, avoid hard agglomeration of particles caused by high temperature aging, and ensure the fluidity of the precursor and the uniformity of subsequent sintering.

[0170] 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 carbonate precursor, characterized in that, The chemical formula of the carbonate precursor is Ni x Co y Mn (1-x-y-α-β) Mg α Zr β CO3, wherein x is 0.15~0.25, y is 0.15~0.25, α is 0.005~0.02, x+y+α+β<1, and the molar ratio of Mg to Zr is 3:1~5:

1.

2. A method for preparing a carbonate precursor, characterized in that, The preparation method includes the following steps: A metal salt solution and a composite precipitant solution are mixed in parallel in the base liquid and co-precipitated. The resulting slurry is then subjected to a first aging and a second aging. After solid-liquid separation, the slurry is washed and dried to obtain the carbonate precursor of claim 1. The temperature for the first aging process is 45℃~55℃; The second aging temperature is 65℃~75℃.

3. The preparation method according to claim 2, characterized in that, The first aging time is 3 to 5 hours; And / or, the second aging time is 1.5h to 2.5h.

4. The preparation method according to claim 2 or 3, characterized in that, The composite precipitant solution includes a first precipitant solution and a second precipitant solution; The first precipitant in the first precipitant solution is sodium carbonate; The second precipitant in the second precipitant solution is ammonium bicarbonate.

5. The preparation method according to claim 4, characterized in that, The volume ratio of the first precipitant solution to the second precipitant solution is 3:1 to 5:1; And / or, the concentration of the first precipitant solution is 1.2 mol / L to 1.8 mol / L; And / or, the concentration of the second precipitant solution is 0.5 mol / L to 0.8 mol / L.

6. The preparation method according to claim 2, characterized in that, The total concentration of metal ions in the metal salt solution is 1 mol / L to 1.5 mol / L; And / or, the metal salts in the metal salt solution include nickel salts, cobalt salts, manganese salts, magnesium salts, and zirconium salts.

7. The preparation method according to claim 2, characterized in that, The temperature for the coprecipitation reaction is 45℃~55℃; And / or, the pH value of the coprecipitation reaction is 8.5~9.5; And / or, the stirring speed of the coprecipitation reaction is 600 rpm to 800 rpm; And / or, during the coprecipitation reaction, the flow rate of the metal salt solution is 5 mL / min to 10 mL / min; And / or, the median particle size at the endpoint of the coprecipitation reaction is 8 μm to 10 μm.

8. The preparation method according to claim 2, characterized in that, The base liquid is composed of water, sodium carbonate and ammonia. And / or, the temperature of the bottom liquid is 45℃~55℃; And / or, the pH value of the substrate solution is 8.5~9.5; And / or, the ammonia concentration of the bottom liquid is 4 g / L to 10 g / L.

9. The preparation method according to claim 2, characterized in that, The drying process includes vacuum drying at a temperature of 100℃~110℃.

10. A positive electrode material, characterized in that, The cathode material is prepared from a carbonate precursor; The carbonate precursor is the carbonate precursor according to claim 1, or the carbonate precursor prepared by the preparation method according to any one of claims 2 to 9.

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