Doped high-nickel precursor with core-shell structure as well as preparation method and application of doped high-nickel precursor

Abstract

The invention provides a high-nickel precursor with a doped core-shell structure as well as a preparation method and application of the high-nickel precursor. The preparation method comprises the following steps: (1) adding a nickel-based main metal salt solution, a first precipitator solution and a first complexing agent solution in a parallel flow manner, carrying out a first-stage nucleation reaction, and then continuing to carry out a first-stage growth reaction; (2) the nickel-based main metal salt solution, the M salt solution with the valence larger than or equal to + 5, the second precipitator solution and the second complexing agent solution are added in a parallel flow mode, a second-stage coprecipitation growth reaction is conducted, and a high-nickel precursor is obtained; the nickel-based main metal salt in the step (1) is consistent with the nickel-based main metal salt in the step (2); in the process that the pH value of the first-stage nucleation reaction is transited to the pH value of the first-stage growth reaction, the decreasing rate of the pH value is smaller than or equal to 0.3 / h and larger than 0 / h; the pH value of the second-stage growth reaction is higher than that of the first-stage growth reaction. According to the invention, the structural stability and the cycling stability of the positive electrode material prepared from the precursor are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a doped core-shell structured high-nickel precursor, a preparation method thereof, and a use thereof. Background Art

[0002] With the continuous growth of the global demand for clean energy and electric vehicles, the market has put forward higher requirements for the energy density and cycle stability of lithium-ion batteries. High-nickel cathode materials such as lithium nickel cobalt manganate (NCM, the molar ratio of nickel in the main metal elements ≥ 80%) have attracted much attention due to their high specific capacity and high working voltage. However, these materials are susceptible to problems such as structural degradation, microcracks, cation mixing, and poor thermal stability during actual charge and discharge processes, resulting in battery performance degradation and safety hazards. Therefore, developing new high-nickel cathode materials and their preparation technologies to improve the comprehensive performance of batteries has become the focus of current research.

[0003] The formation and expansion of microcracks in high-nickel cathode materials are generally considered to be one of the key factors leading to battery performance degradation. These cracks are usually generated due to changes in lattice parameters during charge and discharge processes, especially in materials with high nickel content. Due to the high activity of Ni 4+ reacting with the electrolyte, a NiO-like rock salt phase will be formed, seriously damaging the structure of the layered material. The formation of microcracks will expose new surfaces inside the particles, accelerating structural degradation and affecting the thermal stability, structural stability, and cycle stability of the battery.

[0004] However, recent literature studies have also shown that the surface reaction activity of high-nickel cathode materials has a more critical impact on the cycle life than microcracks. Excessive surface reaction activity will lead to an intensification of side reactions between the cathode material and the electrolyte, such as transition metal dissolution, electrolyte decomposition, etc., resulting in the loss of active substances, rapid capacity decay, and shortening of the battery's cycle life. Appropriate surface reaction activity is conducive to achieving a balance between capacity and cycle performance, while ensuring the rapid insertion and extraction of lithium ions, and improving the reversible capacity and cycle stability of the battery.

[0005] Therefore, how to optimize the microstructure of high-nickel cathode materials to reduce microcracks while also controlling the surface reaction activity of the materials is a technical problem that urgently needs to be solved in the direction of developing high-performance lithium-ion battery cathode materials. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a doped core-shell structured high-nickel precursor, its preparation method and use. The preparation method provided by the present invention enables the obtained high-nickel precursor material to eliminate microcracks in the material while avoiding the structural collapse caused by the obvious difference in lattice parameters at the core-shell junction, and also adjusts the electronic structure of the outer shell layer, appropriately reducing the surface reaction activity, thereby significantly improving the structural stability and cycling stability of the cathode material prepared from this precursor.

[0007] To achieve the object of this invention, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of a doped core-shell structured high-nickel precursor, and the preparation method includes the following steps:

[0009] (1) A nickel-based main metal salt solution, a first precipitating agent solution and a first complexing agent solution are added in parallel flow, first a first-stage co-precipitation nucleation reaction is carried out, and then a first-stage co-precipitation growth reaction is continued to obtain a core precursor;

[0010] (2) A nickel-based main metal salt solution, a dopant M salt solution, a second precipitating agent solution and a second complexing agent solution are added in parallel flow, and a second-stage co-precipitation growth reaction is carried out on the surface of the core precursor to obtain the doped core-shell structured high-nickel precursor;

[0011] Wherein, the nickel-based main metal salt in step (1) is exactly the same as the nickel-based main metal salt in step (2), and the valence of element M in the M salt is ≥ +5; during the process of the pH value of the first-stage co-precipitation nucleation reaction transitioning to the pH value of the first-stage co-precipitation growth reaction, the rate of decrease of the pH value ≤ 0.3 / h and > 0 / h; the pH value of the second-stage co-precipitation growth reaction in step (2) is higher than the pH value of the first-stage co-precipitation growth reaction in step (1).

[0012] For example, the valence of M can be +5 or +6; the rate of decrease can be 0.01 / h, 0.05 / h, 0.1 / h, 0.15 / h, 0.2 / h, 0.25 / h or 0.3 / h, etc.

[0013] It should be noted that the high nickel in the high-nickel precursor in the present invention refers to that in the nickel-based main metal salt solution, the proportion of nickel in the total molar amount of all main metals ≥ 80%.

[0014] In the preparation method provided by the present invention, through the staged coprecipitation reaction, in the first stage of preparing the core, no doping is carried out, and the decrease rate of the pH value during the nucleation to growth process is controlled not to exceed 0.3 / h, realizing the natural transition from the nucleation stage to the growth stage and avoiding the appearance of microcracks in the core; in the second stage of preparing the shell, on the basis that the main metal element of the core is completely consistent, doping of high-valence elements (≥ +5 valence) is carried out, and at the same time, the pH value during the growth process of the second stage is controlled to be slightly higher than that during the growth process of the first stage. On the one hand, since the main metal elements of the core and the shell are the same, there will be no significant difference in lattice parameters, and in coordination with the control of the pH value during the preparation process, the precursor material retains a consistent radial alignment structure from the inside to the outside; this structural design eliminates microcracks in the material while avoiding the structural collapse caused by the obvious difference in lattice parameters at the core-shell junction, and also adjusts the electronic structure of the shell by doping high-valence elements in the second stage, appropriately reducing the surface reaction activity; the synergistic effect of the above-mentioned multiple factors optimizes the microstructure of the high-nickel cathode material to reduce microcracks, controls the surface reaction activity of the material, and at the same time makes the sphericity of the obtained precursor relatively high; thereby significantly improving the structural stability and cycle stability of the high-nickel cathode material obtained from the precursor material; moreover, the preparation method provided by the present invention has simple and controllable process operations and is easy for large-scale production.

[0015] In the present invention, except for the doping of the M salt in the second stage, the decrease rate of the pH value in the first stage and the condition that the pH value in the second stage is slightly higher than that during the growth process of the first stage must be satisfied simultaneously to achieve the preparation of a precursor with grains arranged in a consistent radial direction, without microcracks, and with good control of surface activity.

[0016] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved.

[0017] Preferably, based on the total molar amount of all metal elements in the nickel-based main metal salt described in step (1) being 100%, the molar ratio of the nickel element is 80% - 98%, such as 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98%, etc.

[0018] Preferably, in the nickel-based main metal salt described in step (1), in addition to the nickel element, it also includes manganese element and / or cobalt element.

[0019] It should be noted that the present invention does not specifically limit the type of the nickel-based main metal salt. The types of metal salts in conventional coprecipitation reactions are all applicable to the present invention. For example, the metal salt includes but is not limited to at least one of nickel-based main metal sulfate, nickel-based main metal nitrate, nickel-based main metal chloride, or nickel-based main metal acetate, etc.

[0020] Preferably, in step (1), the concentration of the nickel-based main metal salt solution is 1 to 3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc.

[0021] Preferably, in step (2), the M element in the M salt includes any one or a combination of at least two of vanadium, niobium, or tungsten.

[0022] In the present invention, doping with at least one of vanadium salt, tungsten salt, or niobium salt can better exert the control of the surface activity by the high-valence element, and at the same time can more effectively inhibit the appearance of microcracks. Moreover, the specific salt types of the M salt in the present invention are also conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments according to actual needs, such as at least one of tungstate, niobate, or vanadate, etc.

[0023] Exemplarily, the present invention provides the following specific types of the doping agent M salt:

[0024] At least one of sodium vanadate (NaVO3), ammonium vanadate (NH4VO3), sodium niobate (NaNbO3), potassium niobate (KNbO3), sodium tungstate (Na2WO4), or ammonium tungstate ((NH4)2WO4), etc.

[0025] Preferably, in step (2), the concentration of the doping agent M salt solution is 0.01 to 1 mol / L, such as 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L, etc., and preferably 0.05 to 0.2 mol / L.

[0026] Preferably, in step (2), taking the total molar amount of the metal element and the M element in the nickel-based main metal salt solution as 100%, the molar amount ratio of the M element is 0 to 10% and does not include 0%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10%, etc.

[0027] In the present invention, the molar doping amount (i.e., the molar ratio) of element M in the second stage is 0 to 10% and does not include 0%, that is, trace doping is carried out, which will not cause too large a difference in lattice parameters, so that a consistent radial alignment structure is retained inside and outside. This structural design eliminates microcracks in the material while avoiding structural collapse at the core-shell connection due to obvious differences in lattice parameters, and better improves the structural stability and cycling stability of the cathode material.

[0028] Preferably, the mass fractions of the first precipitating agent solution in step (1) and the second precipitating agent solution in step (2) are each independently 10% to 40%, such as 10%, 15%, 20%, 25%, 30%, 35% or 40%, etc.

[0029] Preferably, the mass fractions of the first complexing agent solution in step (1) and the second complexing agent solution in step (2) are each independently 10% to 20%, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc.

[0030] It should be noted that the types of substances of the first precipitating agent and the second precipitating agent in the present invention are both conventional technical solutions, and in the preparation process, the two can be exactly the same or independent of each other without affecting each other; similarly, the first complexing agent and the second complexing agent are also the same; those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0031] Furthermore, the selection of the types of substances of the precipitating agent and the complexing agent in the present invention is a conventional technical solution:

[0032] For example, the precipitating agent can be a hydroxide or a carbonate, including but not limited to at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide or sodium carbonate, and more preferably a sodium hydroxide solution.

[0033] For example, the complexing agent can be at least one of ammonia water, ammonium carbonate, ammonium bicarbonate, oxalic acid or ethylenediaminetetraacetic acid (EDTA), and more preferably ammonia water.

[0034] Preferably, the pH value of the coprecipitation nucleation reaction in the first stage in step (1) is 11.6 to 12.6, such as 11.6, 11.7, 11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5 or 12.6, etc.

[0035] Preferably, the reaction time of the coprecipitation nucleation reaction in the first stage is 4 to 8 h, such as 4 h, 5 h, 6 h, 7 h or 8 h, etc.

[0036] Preferably, the pH value of the coprecipitation growth reaction in the first stage of step (1) is 9.3 to 10.8, such as 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7 or 10.8, etc., and preferably 9.6 to 10.4.

[0037] Preferably, the median particle size D501 of the core precursor in step (1) is 4 to 16 μm, such as 4 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 13 μm, 14 μm, 15 μm or 16 μm, etc., and preferably 6 to 12 μm.

[0038] Preferably, the difference between the pH value of the coprecipitation growth reaction in the second stage of step (2) and the pH value of the coprecipitation growth reaction in the first stage of step (1) is 0.3 to 0.6, such as 0.3, 0.4, 0.5 or 0.6, etc.

[0039] In the present invention, further adjusting the difference between the pH value of the coprecipitation growth reaction in the second stage of step (2) and the pH value of the coprecipitation growth reaction in the first stage of step (1) to be 0.3 to 0.6 can better achieve the uniform coprecipitation of the high-valence doped element and the main element in the outer shell layer, and appropriately reduce the porosity of the outer shell layer, so as to effectively reduce the surface reaction activity of the material during charge and discharge.

[0040] Preferably, the pH value of the coprecipitation growth reaction in the second stage of step (2) is 9.6 to 11.4, such as 9.6, 9.9, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3 or 11.4, etc., and preferably 9.9 to 11.

[0041] Preferably, during all processes of the coprecipitation in step (1) and all processes of the coprecipitation in step (2), the reaction temperature is independently 40 to 8%26deg;C, such as 40%26deg;C, 50%26deg;C, 60%26deg;C, 70%26deg;C or 80%26deg;C, etc.

[0042] Preferably, during all processes of the coprecipitation in step (1) and all processes of the coprecipitation in step (2), the stirring speed during the reaction process is independently 100 to 600 rpm, such as 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm, etc.

[0043] Preferably, after the coprecipitation growth reaction in the second stage described in step (2) is completed, the reaction product is washed and dried in sequence to obtain the doped core-shell structured high-nickel precursor.

[0044] Preferably, the difference between the median particle size D502 of the doped core-shell structured high-nickel precursor and the median particle size D501 of the inner core: D502 - D501 = 0.1 - 4 μm, such as 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, 3.3 μm, 3.5 μm, 3.8 μm or 4 μm, etc.

[0045] In the present invention, by further restricting D502 - D501 = 0.1 - 4 μm, the thickness and particle size of the shell layer are regulated. If the thickness of the doped outer shell layer is too thick, the charge-discharge capacity may decrease to a certain extent, while if the thickness of the doped outer shell layer is too thin, the reaction activity on the material surface may still be strong, and the side reaction with the electrolyte is not significantly inhibited, resulting in no obvious improvement in cycle stability.

[0046] The median particle size D502 of the doped core-shell structured high-nickel precursor is 5 - 20 μm, such as 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc., and preferably 6 - 14 μm.

[0047] As a preferred technical solution, the preparation method includes the following steps:

[0048] (1) The nickel-based main metal salt solution, the first precipitant solution and the first complexing agent solution are added in parallel flow, first a first-stage coprecipitation nucleation reaction with a pH value of 11.6 - 12.6 is carried out, and then a first-stage coprecipitation growth reaction with a pH value of 9.6 - 10.4 is continued to obtain an inner core precursor with a median particle size D501 of 6 - 12 μm;

[0049] (2) The nickel-based main metal salt solution, the dopant M salt solution, the second precipitant solution and the second complexing agent solution are added in parallel flow, and a second-stage coprecipitation growth reaction is carried out on the surface of the inner core precursor. The pH value of the second-stage coprecipitation growth reaction is higher than that of the first-stage coprecipitation growth reaction, and the difference is 0.3 - 0.6, to obtain a doped core-shell structured high-nickel precursor with a median particle size D502 of 6 - 14 μm, where D502 - D501 = 0.1 - 4 μm;

[0050] Among them, based on the total molar amount of all metal elements in the nickel-based main metal salt described in step (1) being 100%, the molar amount ratio of the nickel element is 80% - 98%; the nickel-based main metal salt described in step (1) is exactly the same as the nickel-based main metal salt described in step (2), and the valence of the M element in the M salt is ≥ +5; based on the total molar amount of the metal element and the M element in the nickel-based main metal salt solution being 100%, the molar amount ratio of the M element is 0 - 10% and does not include 0%; during the process of the pH value of the coprecipitation nucleation reaction in the first stage transitioning to the pH value of the coprecipitation growth reaction in the first stage, the decreasing rate of the pH value is ≤ 0.3 / h and > 0 / h.

[0051] It should be noted that:

[0052] The reaction atmosphere in the present invention includes a protective atmosphere, such as a nitrogen atmosphere and / or an inert atmosphere, etc.; the inert gas includes but is not limited to argon or helium, etc.

[0053] The reaction process of the present invention can be carried out in a bottom liquid, and the bottom liquid includes a mixed solution containing a precipitant, a complexing agent, and water, with a pH of 11.5 - 12.8, such as 11.5, 11.8, 12, 12.3, 12.5, or 12.8, etc., and the concentration of the complexing agent is 1 - 10 g / L, such as 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, or 10 g / L, etc.

[0054] In a second aspect, the present invention provides a doped core-shell structured high-nickel precursor, and the doped core-shell structured high-nickel precursor is prepared by the preparation method as described in the first aspect;

[0055] The doped core-shell structured high-nickel precursor includes a core and a shell layer located on the surface of the core; the core includes a nickel-based precursor material, and the shell layer includes a nickel-based precursor material and a doping element M doped in the nickel-based precursor material;

[0056] From the core of the core to the shell layer direction, the crystal grains in the doped core-shell structured high-nickel precursor are radially distributed.

[0057] The high-nickel precursor provided by the present invention has crystal grains that are uniformly radially distributed from the core to the shell layer, without microcracks inside, and with a moderate surface activity degree.

[0058] Preferably, the chemical general formula of the core is (Ni x Co y Mn 1-x-y )(OH)2, and the chemical general formula of the shell layer is [Ni x Coy Mn 1-x-y 1-z M z (OH) 2+δ , wherein 0.80 ≤ x ≤ 0.98, 0 ≤ y < 0.20, 0 < z ≤ 0.10, δ ≥ 0, and the valence of M is ≥ +5.

[0059] For example, x may be 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, or 0.98, etc.; y may be 0, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.2, etc.; z may be 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, etc.; δ is adaptively selected and adjusted according to the specific type and addition amount of the M element.

[0060] In a third aspect, the present invention provides a cathode material, which is obtained by mixing and sintering a doped core-shell structured high-nickel precursor as described in the second aspect with a lithium source.

[0061] In the present invention, the preparation process of the cathode material prepared from the doped core-shell structured high-nickel precursor provided in the second aspect is a conventional technical solution, and the present invention is applicable to the preparation methods of cathode materials obtained from cathode precursor materials that can be known within a reasonable range by those skilled in the art.

[0062] Exemplarily, the present invention provides a specific preparation method of a cathode material:

[0063] Mix a lithium source and the doped core-shell structured high-nickel precursor as described in the second aspect, and perform sintering treatment to obtain the cathode material.

[0064] Preferably, the molar ratio of lithium in the high-nickel ternary cathode material precursor to the lithium in the lithium source is 1:(1 - 1.08), such as 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, or 1:1.08, etc.

[0065] Preferably, the sintering treatment is carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere includes an oxygen atmosphere and / or an air atmosphere, etc.

[0066] Preferably, the sintering treatment includes a first sintering treatment and a second sintering treatment.

[0067] ​Preferably, the sintering temperature of the first sintering treatment is 450 - 650 °C, such as 450 °C, 500 °C, 550 °C, 600 °C or 650 °C, etc., and the sintering time is 8 - 20 h, such as 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h, etc.

[0068] Preferably, the sintering temperature of the second sintering treatment is 650 - 950 °C, such as 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C or 950 °C, etc., and the sintering time is 6 - 20 h, such as 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h, etc.

[0069] In a fourth aspect, the present invention further provides a lithium - ion battery, and the lithium - ion battery includes the positive electrode material as described in the third aspect.

[0070] The numerical ranges described in the present invention not only include the point values exemplified above, but also include any point values between the above - mentioned numerical ranges that are not exemplified. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] In the preparation method provided by the present invention, through a staged co - precipitation reaction, in the first stage of preparing the core, no doping is carried out, and the pH value decline rate during the nucleation - to - growth process is controlled not to exceed 0.3 / h, realizing a natural transition from the nucleation stage to the growth stage and avoiding the appearance of micro - cracks in the core; while in the second stage of preparing the shell, on the basis of being completely consistent with the main metal element of the core, doping with high - valence elements (≥ + 5 valence) is carried out, and at the same time, the pH value during the growth process of the second stage is controlled to be higher than that of the growth process of the first stage. On the one hand, since the main metal elements of the core and the shell are the same, there will be no significant difference in lattice parameters, and in coordination with the regulation of the pH value during the preparation process, the precursor material retains a consistent radially aligned structure from the inside to the outside; this structural design eliminates micro - cracks in the material while avoiding structural collapse at the core - shell connection due to obvious differences in lattice parameters, and also adjusts the electronic structure of the shell by doping with high - valence elements in the second stage, greatly reducing the surface reaction activity; the synergistic effect of the above - mentioned multiple factors optimizes the microstructure of the high - nickel positive electrode material to reduce micro - cracks, controls the surface reaction activity of the material, and at the same time makes the sphericity of the obtained precursor relatively high; thus, the structural stability and cycle stability of the high - nickel positive electrode material obtained from the precursor material are significantly improved; moreover, the preparation method provided by the present invention has simple and controllable process operations and is easy for large - scale production. Description of the Drawings

[0073] Figure 1 SEM image of the doped core-shell structured high-nickel precursor provided for Example 1

[0074] Figure 2 SEM image of the cross-section of the doped core-shell structured high-nickel precursor provided for Example 1

[0075] Figure 3 SEM image of the doped core-shell structured high-nickel precursor provided for Comparative Example 1

[0076] Figure 4 SEM image of the cross-section of the doped core-shell structured high-nickel precursor provided for Comparative Example 1

[0077] Figure 5 SEM image of the doped core-shell structured high-nickel precursor provided for Comparative Example 2

[0078] Figure 6 SEM image of the cross-section of the doped core-shell structured high-nickel precursor provided for Comparative Example 2 Detailed Description of the Invention

[0079] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0081] In the description of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two unless otherwise specifically defined.

[0082] Example 1

[0083] This example provides a method for preparing a doped core-shell structured high-nickel precursor, and the preparation method is as follows:

[0084] (1) According to the molecular formula Ni 0.96 Co 0.02 Mn 0.02Prepare a nickel-based mixed metal sulfate solution with (OH)₂, where the total metal ion concentration is 2 mol / L; prepare a sodium tungstate solution with a concentration of 0.1 mol / L as the dopant solution; prepare an ammonia water solution with a mass concentration of 14% as the first complexing agent solution and the second complexing agent solution, and prepare a sodium hydroxide solution with a mass concentration of 25% as the first precipitating agent solution and the second precipitating agent solution. Mix concentrated ammonia water, sodium hydroxide solution and 20 L of pure water to prepare a reaction bottom solution with pH = 12.0 - 12.2 and ammonia water concentration of 3 - 4 g / L.

[0085] (2) Under the protection of a nitrogen atmosphere, add the prepared nickel-based mixed metal sulfate solution, sodium hydroxide solution and ammonia water solution into a 50 L reaction kettle containing the bottom solution at a co-current flow rate of 1.5 L / h, 0.64 L / h and 0.20 L / h respectively to carry out the first-stage co-precipitation nucleation reaction. Control the pH = 12.2 ± 0.1 during the nucleation stage and maintain it for 6 h; after the nucleation is completed, adjust the flow rate of the sodium hydroxide solution to make the pH of the reaction system drop to pH = 10.0 ± 0.1 at a rate of 0.2 / h to carry out the first-stage co-precipitation growth reaction, and continue the reaction until the median particle size D501 in the inner core reaches D501 = 10 μm.

[0086] (3) After the first-stage co-precipitation growth reaction is completed, on the basis of the original feed raw materials, add the sodium tungstate dopant solution. By controlling the feed rate of the sodium tungstate dopant solution, make the ratio of the total molar amount of Ni, Co, and Mn elements to the feed molar amount of W element 0.995:0.005, and adjust the flow rate of the sodium hydroxide solution to make the pH of the reaction system reach the pH = 10.4 ± 0.1 of the second growth stage in about 4 h, so that the difference in pH value between the second-stage co-precipitation growth reaction and the first-stage co-precipitation growth reaction is 0.4, and continue the second-stage co-precipitation growth reaction; stop feeding when the median particle size D502 reaches D502 = 12.0 μm; after the slurry is washed three times with dilute sodium hydroxide solution and three times with hot pure water, dry it at 100 °C for 12 h to obtain the doped core-shell structured high-nickel precursor.

[0087] The doped core-shell structured high-nickel precursor includes an inner core (Ni 0.96 Co 0.02 Mn 0.02 (OH)₂) and a shell layer ([Ni 0.96 Co 0.02 Mn 0.02 ) 0.995 W 0.005 (OH) 2.02);The core includes a nickel-based precursor material, and the shell includes a nickel-based precursor material and a doping element W doped in the nickel-based precursor material. From the core of the core to the shell direction, the crystal grains in the high-nickel precursor of the doped core-shell structure are radially distributed;

[0088] The reaction temperature of the entire coprecipitation reaction is maintained at 55 ± 1 °C, the stirring speed is 300 rpm, and the ammonia concentration is maintained at 3 - 4 g / L.

[0089] Example 2

[0090] This example provides a method for preparing a high-nickel precursor with a doped core-shell structure, and the preparation method is as follows:

[0091] (1) Prepare a nickel-based mixed metal sulfate solution according to the molecular formula Ni 0.96 Co 0.02 Mn 0.02 (OH)2, with the total metal ion concentration being 3 mol / L; prepare a sodium tungstate solution with a concentration of 0.2 mol / L as the doping agent solution; prepare an ammonia water solution with a mass concentration of 20% as the first complexing agent solution and the second complexing agent solution, and prepare a sodium hydroxide solution with a mass concentration of 35% as the first precipitating agent solution and the second precipitating agent solution. Prepare a solution with pH = 12.0 - 12.2 and ammonia concentration of 3 - 4 g / L by mixing concentrated ammonia water, sodium hydroxide solution and 20 L of pure water as the reaction bottom liquid;

[0092] (2) Under the protection of a nitrogen atmosphere, the prepared nickel-based mixed metal sulfate solution, sodium hydroxide solution and ammonia water solution are respectively added into a 50 L reaction kettle containing the bottom liquid at a flow rate of 1.5 L / h, 0.64 L / h and 0.20 L / h for the first-stage coprecipitation nucleation reaction. During the nucleation stage, control pH = 11.8 ± 0.1 and maintain it for 6 h; after the nucleation is completed, adjust the flow rate of the sodium hydroxide solution to make the pH of the reaction system decrease at a rate of 0.3 / h to pH = 9.8 ± 0.1 for the first-stage coprecipitation growth reaction. Continue the reaction until the median particle size D501 in the core reaches D501 = 6 μm;

[0093] (3) After the co-precipitation growth reaction in the first stage is completed, on the basis of the original feedstock, a sodium tungstate dopant solution is added. By controlling the feeding rate of the sodium tungstate dopant solution, the ratio of the total molar amount of the three elements Ni, Co, and Mn to the feeding molar amount of the W element is 0.995:0.005, and the flow rate of the sodium hydroxide solution is adjusted so that the pH of the reaction system reaches pH = 10.4 ± 0.1 in the second growth stage in about 4 h, making the difference in pH values between the co-precipitation growth reaction in the second stage and that in the first stage 0.6. Then, the co-precipitation growth reaction in the second stage is continued; when the median particle size D502 of the particles reaches D502 = 10 μm, the feeding is stopped; after the slurry is washed three times with dilute sodium hydroxide solution and three times with hot pure water, it is dried at 100 °C for 12 h to obtain the doped core-shell structured high-nickel precursor.

[0094] The doped core-shell structured high-nickel precursor includes a core (Ni 0.96 Co 0.02 Mn 0.02 (OH)2) and a shell layer ([Ni 0.96 Co 0.02 Mn 0.02 ) located on the surface of the core; the core includes a nickel-based precursor material, and the shell layer includes a nickel-based precursor material and a doping element W doped in the nickel-based precursor material. From the core of the core to the shell layer direction, the crystal grains in the doped core-shell structured high-nickel precursor are radially distributed. 0.995 W 0.005 (OH) 2.02 );The core includes a nickel-based precursor material, and the shell layer includes a nickel-based precursor material and a doping element W doped in the nickel-based precursor material. From the core of the core to the shell layer direction, the crystal grains in the doped core-shell structured high-nickel precursor are radially distributed.

[0095] The reaction temperature of the entire co-precipitation reaction is maintained at 40 ± 1 °C, the stirring speed is 400 rpm, and the ammonia concentration is maintained at 3 - 4 g / L.

[0096] Example 3

[0097] This example provides a preparation method of a doped core-shell structured high-nickel precursor. The preparation method is as follows:

[0098] (1) Prepare a nickel-based mixed metal sulfate solution according to the molecular formula Ni 0.96 Co 0.02 Mn 0.02 (OH)2, with the total metal ion concentration being 1 mol / L; prepare a sodium tungstate solution with a concentration of 0.1 mol / L as the dopant solution; prepare an ammonia water solution with a mass concentration of 10% as the first complexing agent solution and the second complexing agent solution, and prepare a sodium hydroxide solution with a mass concentration of 20% as the first precipitating agent solution and the second precipitating agent solution. Prepare a solution with pH = 12.0 - 12.2 and ammonia concentration of 3 - 4 g / L by mixing concentrated ammonia water, sodium hydroxide solution and 20 L of pure water as the reaction bottom liquid.

[0099] (2) Under the protection of a nitrogen atmosphere, the prepared nickel-based mixed metal sulfate solution, sodium hydroxide solution, and ammonia water solution were co-fed into a 50 L reactor containing a bottom solution at flow rates of 1.5 L / h, 0.64 L / h, and 0.20 L / h respectively to carry out the first-stage coprecipitation nucleation reaction. During the nucleation stage, the pH was controlled at 12.0 ± 0.1 and maintained for 6 h; after nucleation, the flow rate of the sodium hydroxide solution was adjusted to make the pH of the reaction system decrease to pH = 10.2 ± 0.1 at a rate of 0.1 / h, and the first-stage coprecipitation growth reaction was carried out. Continue the reaction until the median particle size D501 in the core reached D501 = 12 μm;

[0100] (3) After the first-stage coprecipitation growth reaction ended, on the basis of the original feed materials, a sodium tungstate dopant solution was added. By controlling the feed rate of the sodium tungstate dopant solution, the ratio of the total molar amount of the three elements Ni, Co, and Mn to the feed molar amount of the W element was 0.995:0.005, and the flow rate of the sodium hydroxide solution was adjusted to make the pH of the reaction system reach pH = 10.7 ± 0.1 in the second growth stage in about 4 h, so that the difference in pH value between the second-stage coprecipitation growth reaction and the first-stage coprecipitation growth reaction was 0.5, and the second-stage coprecipitation growth reaction was continued; when the median particle size D502 reached D502 = 13 μm, the feeding was stopped; the slurry was washed three times with dilute sodium hydroxide solution and three times with hot pure water, and then dried at 100 °C for 12 h to obtain the doped core-shell structured high-nickel precursor;

[0101] The doped core-shell structured high-nickel precursor includes a core (Ni 0.96 Co 0.02 Mn 0.02 (OH)2) and a shell layer ([Ni 0.96 Co 0.02 Mn 0.02 ) 0.995 W 0.005 (OH) 2.02 ) located on the surface of the core; the core includes a nickel-based precursor material, and the shell layer includes a nickel-based precursor material and a doping element W doped in the nickel-based precursor material. From the core of the core to the shell layer direction, the crystal grains in the doped core-shell structured high-nickel precursor are radially distributed;

[0102] The reaction temperature of the entire coprecipitation reaction was maintained at 55 ± 1 °C, the stirring speed was 300 rpm, and the ammonia concentration was maintained at 3 - 4 g / L.

[0103] Example 4

[0104] The difference between this embodiment and Embodiment 1 is that in step (1) of this embodiment, a nickel-based mixed metal sulfate solution is prepared according to the molecular formula Ni 0.90 Co 0.05 Mn 0.05 (OH)2, and the dopant solution is adjusted to a sodium vanadate (NaVO3) solution;

[0105] In step (3), by controlling the feeding rate of the sodium vanadate dopant solution, the ratio of the total molar amount of the three elements of Ni, Co to the feeding molar amount of the V element is 0.95:0.05.

[0106] In the structure of the product prepared, the doped core-shell structured high-nickel precursor includes a core (Ni 0.90 Co 0.05 Mn 0.05 (OH)2) and a shell layer ([Ni 0.90 Co 0.05 Mn 0.05 ) located on the surface of the core 0.95 V 0.05 (OH) 2.15 ).

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

[0108] Embodiment 5

[0109] The difference between this embodiment and Embodiment 1 is that in step (3) of this embodiment, by controlling the feeding rate of the sodium tungstate dopant solution, the ratio of the total molar amount of the three elements of Ni, Co, Mn to the feeding molar amount of the W element is 0.90:0.1.

[0110] In the structure of the product prepared, the doped core-shell structured high-nickel precursor includes a core (Ni 0.96 Co 0.02 Mn 0.02 (OH)2) and a shell layer ([Ni 0.96 Co 0.02 Mn 0.02 ) located on the surface of the core 0.9 W 0.1 (OH) 2.4 ).

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

[0112] Embodiment 6

[0113] The difference between this embodiment and Embodiment 1 is that in step (3) of this embodiment, by controlling the feeding rate of the sodium tungstate dopant solution, the ratio of the total molar amount of the three elements of Ni, Co, Mn to the feeding molar amount of the W element is 0.85:0.15.

[0114] In the structure of the prepared product, the high-nickel precursor of the doped core-shell structure includes a core (Ni 0.96 Co 0.02 Mn 0.02 (OH)2) and a shell layer ([Ni 0.96 Co 0.02 Mn 0.02 ) located on the surface of the core. 0.85 W 0.15 (OH) 2.6 ).

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

[0116] Example 7

[0117] The difference between this example and Example 1 is that in step (2) of this example, the reaction continues until the median particle size D501 in the core reaches D501 = 7 μm, and the coprecipitation growth reaction in the first stage ends, that is, D502 - D501 = 5 μm.

[0118] The remaining preparation methods and parameters are the same as those in Example 1.

[0119] Example 8

[0120] The difference between this example and Example 1 is that in step (3) of this example, the difference in pH value between the coprecipitation growth reaction in the second stage and the coprecipitation growth reaction in the first stage is 0.2.

[0121] The remaining preparation methods and parameters are the same as those in Example 1.

[0122] Example 9

[0123] The difference between this example and Example 1 is that in step (3) of this example, the difference in pH value between the coprecipitation growth reaction in the second stage and the coprecipitation growth reaction in the first stage is 0.7.

[0124] The remaining preparation methods and parameters are the same as those in Example 1.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, a sodium tungstate dopant solution is not prepared;

[0127] In step (3), the dopant solution is not added either, that is, tungsten element doping is not carried out.

[0128] The remaining preparation methods and parameters are the same as those in Example 1.

[0129] Comparative Example 2

[0130] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, during the transition from the first-stage coprecipitation nucleation reaction to the first-stage coprecipitation growth reaction, the pH value drops at a rate of 0.5 / h, and the pH of the first-stage coprecipitation growth reaction is 11.0 ± 0.1, that is, higher than the pH value of the second-stage coprecipitation growth reaction.

[0131] The remaining preparation methods and parameters are the same as those in Example 1.

[0132] Comparative Example 3

[0133] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, during the transition from the first-stage coprecipitation nucleation reaction to the first-stage coprecipitation growth reaction, the pH value drops at a rate of 0.5 / h.

[0134] The remaining preparation methods and parameters are the same as those in Example 1.

[0135] Comparative Example 4

[0136] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, the pH of the first-stage coprecipitation growth reaction is 11.0 ± 0.1, that is, higher than the pH value of the second-stage coprecipitation growth reaction.

[0137] The remaining preparation methods and parameters are the same as those in Example 1.

[0138] Figure 1 The SEM image of the doped core-shell structured high-nickel precursor provided in Example 1 is shown.

[0139] Figure 2 The SEM image of the cross-section of the doped core-shell structured high-nickel precursor provided in Example 1 is shown.

[0140] From Figure 1 and Figure 2 it can be seen that the doped core-shell structured high-nickel precursor obtained by the preparation method provided by the present invention has a high sphericity, no cracks inside, relatively fine primary grains and dense arrangement, the primary grains of the inner core are radially arranged, and the outer shell continues to extend, presenting a consistent radially aligned structure of the internal grains.

[0141] Figure 3 The SEM image of the doped core-shell structured high-nickel precursor provided in Comparative Example 1 is shown.

[0142] Figure 4 The SEM image of the cross-section of the doped core-shell structured high-nickel precursor provided in Comparative Example 1 is shown.

[0143] From Figure 3 andFigure 4 It can be seen that during the preparation of the high-nickel precursor, without doping and preparing the high-valence dopant in the shell preparation stage, although a material with high sphericity is obtained, its internal structure is relatively loose, and its structural stability and cycle stability are poor.

[0144] Figure 5 The SEM image of the doped core-shell structured high-nickel precursor provided in Comparative Example 2 is shown.

[0145] Figure 6 The SEM image of the cross-section of the doped core-shell structured high-nickel precursor provided in Comparative Example 2 is shown.

[0146] From Figure 5 and Figure 6 It can be seen that during the preparation of the high-nickel precursor, without regulating the pH value drop rate from nucleation to growth stage, and when the pH value of the second-stage coprecipitation growth reaction is lower than that of the first-stage coprecipitation growth reaction, problems such as cracks in the inner core and shell and disordered arrangement of primary grains will occur.

[0147] [Preparation and Performance Testing of Batteries]

[0148] (I) Preparation of the positive electrode material: Weigh and mix evenly the doped core-shell structured high-nickel precursors provided in Examples 1-9 and Comparative Examples 1-4 and lithium carbonate powder in a molar ratio of Li / Me = 1.05:1, and perform two-end solid-phase sintering in an oxygen atmosphere, namely the first sintering, the second sintering, and the third sintering;

[0149] The first sintering is to increase the temperature from room temperature to 500 °C at a heating rate of 4 °C / min and hold for 6 h, the second sintering is to increase the temperature from 500 °C to 900 °C at a heating rate of 3 °C / min and hold for 12 h. After the sintering is completed, the sample is naturally cooled to room temperature in the furnace. After the sample is crushed and passed through a 300-mesh sieve, the positive electrode material is obtained.

[0150] (II) Preparation of the battery, respectively providing a positive electrode plate, a negative electrode plate, a separator, and an electrolyte for the preparation of the battery:

[0151] Preparation of the positive electrode plate: Prepare a positive electrode slurry according to the ratio of positive electrode material:SP:PVDF = 90:5:5, and obtain the positive electrode slurry for standby, where the solid content of the slurry is 60%; Place the aluminum foil on the coater, use a 150-μm coating applicator to place on the aluminum foil, pour in the single-crystal slurry, turn on the equipment for coating, and after the coating is completed, obtain the electrode plate. Place the electrode plate in an oven at 110 °C for drying and rolling to obtain the positive electrode plate;

[0152] In a dry environment, a stamping machine was used to cut the positive electrode sheets provided in the examples and comparative examples into circular sheets with a diameter of 15 mm. In a glove box, a lithium metal sheet was used as the counter electrode, the separator was a ceglard composite membrane, and an electrolyte was added to assemble a button cell; the electrolyte was an organic solution obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 30:50:20, and the concentration of the lithium salt (lithium hexafluorophosphate) in the electrolyte was 1.15 mol / L.

[0153] (III) Performance testing:

[0154] The performance of the button cells provided in Examples 1-9 and Comparative Examples 1-4 was tested using the Wuhan Blue Electric CT2001A system: activated 3 times at a rate of 0.1C / 2.7-4.3V, and then the activated button cells were electrochemically tested under the conditions of 2.7-4.3V@0.1C / 1C to obtain the discharge specific capacity at 0.1C and 1C rates and the capacity retention rate after 100 cycles at 1C rate.

[0155] The test results of the above tests are shown in Table 1.

[0156] Table 1

[0157]

[0158] In summary, in the preparation method provided by the present invention, by carrying out the coprecipitation reaction in stages, in the first stage of preparing the inner core, no doping was carried out, and the pH value decrease rate during the nucleation to growth process was controlled not to exceed 0.3 / h, realizing the natural transition from nucleation to growth stage and avoiding the appearance of microcracks in the inner core; while in the second stage of preparing the shell layer, on the basis of completely maintaining the same main metal element as the inner core, doping with high-valence elements (≥+5 valence) was carried out, and at the same time, the pH value during the growth process of the second stage was controlled to be higher than that of the growth process of the first stage. On the one hand, since the main metal elements of the inner core and the shell layer are the same, there will be no significant difference in lattice parameters, and in coordination with the control of the pH value during the preparation process, the precursor material retains a consistent radially aligned structure from the inside to the outside; this structural design eliminates microcracks in the material while avoiding structural collapse at the core-shell connection due to obvious differences in lattice parameters, and also adjusts the electronic structure of the shell layer by doping with high-valence elements in the second stage, greatly reducing the surface reactivity; the above-mentioned multi-factor synergistic effect optimizes the microstructure of the high-nickel cathode material to reduce microcracks, controls the surface reactivity of the material, and at the same time makes the sphericity of the obtained precursor relatively high; thus, the structural stability and cycle stability of the high-nickel cathode material obtained from the precursor material are significantly improved; moreover, the preparation method provided by the present invention has simple and controllable process operations and is easy for large-scale production.

[0159] The applicant declares that the above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a doped core-shell structured high-nickel precursor, characterized in that, The preparation method includes the following steps: (1) The nickel-based main metal salt solution, the first precipitant solution and the first complexing agent solution are added in parallel flow, first a co-precipitation nucleation reaction in the first stage is carried out, and then a co-precipitation growth reaction in the first stage is continued to obtain a core precursor; (2) The nickel-based main metal salt solution, the dopant M salt solution, the second precipitant solution and the second complexing agent solution are added in parallel flow, and a co-precipitation growth reaction in the second stage is carried out on the surface of the core precursor to obtain the high-nickel precursor of the doped core-shell structure; Among them, the nickel-based main metal salt in step (1) is exactly the same as the nickel-based main metal salt in step (2), and the valence of element M in the M salt is ≥ +5; during the process of the pH value of the co-precipitation nucleation reaction in the first stage transitioning to the pH value of the co-precipitation growth reaction in the first stage, the decreasing rate of the pH value is ≤ 0.3 / h and > 0 / h; the pH value of the co-precipitation growth reaction in the second stage in step (2) is higher than the pH value of the co-precipitation growth reaction in the first stage in step (1).

2. The preparation method according to claim 1, characterized in that, Based on the total molar amount of all metal elements in the nickel-based main metal salt in step (1) being 100%, the molar amount ratio of the nickel element is 80% - 98%; Preferably, in the nickel-based main metal salt in step (1), in addition to the nickel element, it also includes manganese element and / or cobalt element; Preferably, in step (1), the concentration of the nickel-based main metal salt solution is 1 - 3 mol / L; Preferably, element M in the M salt in step (2) includes any one or a combination of at least two of vanadium, niobium or tungsten; Preferably, the concentration of the dopant M salt solution in step (2) is 0.01 - 1 mol / L, preferably 0.05 - 0.2 mol / L; Preferably, in step (2), based on the total molar amount of the metal elements and element M in the nickel-based main metal salt solution being 100%, the molar amount ratio of element M is 0 - 10% and does not include 0%; Preferably, the mass fractions of the first precipitant solution in step (1) and the second precipitant solution in step (2) are each independently 10% - 40%; Preferably, the mass fractions of the first complexing agent solution in step (1) and the second complexing agent solution in step (2) are each independently 10% - 20%.

3. The preparation method according to claim 1 or 2, characterized in that, The pH value of the co-precipitation nucleation reaction in the first stage in step (1) is 11.6 - 12.6, and the reaction time of the co-precipitation nucleation reaction in the first stage is 4 - 8 h; Preferably, the pH value of the co-precipitation growth reaction in the first stage in step (1) is 9.3 - 10.8, preferably 9.6 - 10.4; Preferably, the median particle size D501 of the core precursor in step (1) is 4 - 16 μm, preferably 6 - 12 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The difference between the pH value of the co-precipitation growth reaction in the second stage in step (2) and the pH value of the co-precipitation growth reaction in the first stage in step (1) is 0.3 - 0.6; Preferably, the pH value of the co-precipitation growth reaction in the second stage in step (2) is 9.6 - 11.4, preferably 9.9 - 11.

5. The preparation method according to any one of claims 1-4, characterized in that, After the co-precipitation growth reaction in the second stage described in step (2) ends, the reaction product is washed and dried in sequence to obtain the doped core-shell structured high-nickel precursor. Preferably, the difference between the median particle size D502 of the doped core-shell structured high-nickel precursor and the median particle size D501 of the inner core: D502 - D501 = 0.1 - 4 μm; The median particle size D502 of the doped core-shell structured high-nickel precursor is 5 - 20 μm, preferably 6 - 14 μm.

6. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) The nickel-based main metal salt solution, the first precipitant solution, and the first complexing agent solution are added in parallel flow. First, a first-stage co-precipitation nucleation reaction with a pH value of 11.6 - 12.6 is carried out, and then a first-stage co-precipitation growth reaction with a pH value of 9.6 - 10.4 is continued to obtain an inner core precursor with a median particle size D501 of 6 - 12 μm. (2) The nickel-based main metal salt solution, the dopant M salt solution, the second precipitant solution, and the second complexing agent solution are added in parallel flow to carry out a second-stage co-precipitation growth reaction on the surface of the inner core precursor. The pH value of the second-stage co-precipitation growth reaction is higher than that of the first-stage co-precipitation growth reaction, and the difference is 0.3 - 0.6, to obtain a doped core-shell structured high-nickel precursor with a median particle size D502 of 6 - 14 μm, where D502 - D501 = 0.1 - 4 μm; Wherein, based on the total molar amount of all metal elements in the nickel-based main metal salt described in step (1) being 100%, the molar amount ratio of the nickel element is 80% - 98%; the nickel-based main metal salt described in step (1) is exactly the same as the nickel-based main metal salt described in step (2), and the valence of the M element in the M salt ≥ +5; based on the total molar amount of the metal elements and the M element in the nickel-based main metal salt solution being 100%, the molar amount ratio of the M element is 0 - 10% and does not include 0%; during the process of the pH value of the first-stage co-precipitation nucleation reaction transitioning to the pH value of the first-stage co-precipitation growth reaction, the decreasing rate of the pH value ≤ 0.3 / h and > 0 / h.

7. A doped core-shell structured high-nickel precursor, characterized in that, The doped core-shell structured high-nickel precursor is prepared by the preparation method described in any one of claims 1 - 6; The doped core-shell structured high-nickel precursor includes an inner core and a shell layer located on the surface of the inner core; the inner core includes a nickel-based precursor material, and the shell layer includes a nickel-based precursor material and a doping element M doped in the nickel-based precursor material; From the core of the inner core to the direction of the shell layer, the crystal grains in the doped core-shell structured high-nickel precursor are radially distributed.

8. The doped core-shell structured high-nickel precursor according to claim 7, wherein The chemical general formula of the core is (Ni x Co y Mn 1-x-y )(OH)2, and the chemical general formula of the shell is [Ni x Co y Mn 1-x-y 1-z M z (OH) 2+δ , where 0.80 ≤ x ≤ 0.98, 0 ≤ y < 0.20, 0 < z ≤ 0.10, δ ≥ 0, and the valence of M is ≥ +5.​ 9. A cathode material, characterized in that, The positive electrode material is obtained by mixing and sintering the doped core-shell structured high-nickel precursor described in claim 7 or 8 with a lithium source.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material described in claim 9.

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