Positive electrode precursor material with multilayer structure as well as preparation method and application of positive electrode precursor material

Abstract

The invention provides a positive electrode precursor material with a multilayer structure as well as a preparation method and application of the positive electrode precursor material. The preparation method comprises the following steps: firstly, enabling a first mixed metal salt solution, a first precipitant solution and a first complexing agent solution to flow into a base solution in parallel, and carrying out first-stage coprecipitation reaction to obtain a first precursor material; the first mixed metal salt solution, the second mixed metal salt solution, the second precipitant solution and the second complexing agent solution continue to flow in parallel, a second-stage coprecipitation reaction is carried out, and a second precursor material is obtained; and finally, stopping injection of the first mixed metal salt solution, continuing to flow in the second mixed metal salt solution, the third precipitant solution and the third complexing agent solution in parallel, and carrying out a third-stage coprecipitation reaction. According to the invention, the comprehensive performance of the positive electrode precursor material is improved by optimizing the molar percentage content, pH value, ammonia concentration and other parameters of the nickel element in different mixed metal salts in the coprecipitation reaction process of each stage.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials, and in particular relates to a positive electrode precursor material with a multilayer structure, a preparation method thereof, and an application thereof. Background Art

[0002] As an important new energy material system, ternary cathode precursor materials have broad application prospects. Currently, commonly used ternary cathode precursor materials are nickel salts, cobalt salts, and manganese salts as raw materials, and are produced through a certain process to produce nickel-cobalt-manganese hydroxide products. Depending on the different contents of nickel, cobalt, and manganese elements in the ternary cathode precursor materials, the prepared cathode materials are further divided into NCM523, NCM622, and NCM811. These cathode materials have occupied an increasingly important market position in lithium-ion batteries and have become the preferred cathode materials for power batteries and energy storage batteries.

[0003] Among them, traditional nickel-cobalt-manganese ternary positive electrode precursor materials are widely used due to their high capacity characteristics, but they still face many challenges in the research and development process. For example: on the one hand, the synthesis method and process conditions of the ternary positive electrode precursor materials are not clear enough, and there is a lack of systematic research, which makes the preparation of the materials more difficult; on the other hand, the ternary positive electrode precursor materials still have shortcomings in terms of cycle stability and thermal stability, and it is impossible to achieve comprehensive optimization of material performance.

[0004] Therefore, how to structurally design the ternary positive electrode precursor material and combine it with a reasonable preparation process to obtain a ternary positive electrode material with good comprehensive performance to meet the use requirements of high-performance batteries is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a multilayered cathode precursor material, its preparation method, and its application. By optimizing the coprecipitation reaction process at each stage, the present invention produces a cathode precursor material with high tap density, high specific surface area, and good electrochemical performance.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a positive electrode precursor material having a multilayer structure, the preparation method comprising the following steps:

[0008] S1. The first mixed metal salt solution, the first precipitant solution and the first complexing agent solution are passed into the reactor containing the bottom liquid, and the first stage coprecipitation reaction is performed to obtain a first precursor material;

[0009] S2. After the average particle size of the first precursor material reaches the first target particle size, the first mixed metal salt solution, the second mixed metal salt solution, the second precipitant solution, and the second complexing agent solution are continued to be introduced into the reactor and the second stage coprecipitation reaction is performed to obtain a second precursor material;

[0010] S3. After the average particle size of the second precursor material reaches the second target particle size, the injection of the first mixed metal salt solution is stopped, and the second mixed metal salt solution, the third precipitant solution and the third complexing agent solution are continued to be introduced into the reactor in parallel to perform a third stage coprecipitation reaction. After the average particle size of the particles reaches the third target particle size, the positive electrode precursor material having a multilayer structure is obtained;

[0011] In which, the molar percentage of nickel element in the first mixed metal salt solution is higher than the molar percentage of nickel element in the second mixed metal salt solution, and the pH value of the first stage co-precipitation reaction is higher than the pH value of the second stage co-precipitation reaction and the third stage co-precipitation reaction, and the ammonia concentration in the first stage co-precipitation reaction is not higher than the ammonia concentration in the second stage co-precipitation reaction and the third stage co-precipitation reaction.

[0012] The preparation method of the positive electrode precursor material provided by the present invention is based on the principle of coprecipitation. By controlling the pH value and ammonia concentration changes of the coprecipitation reaction at different stages to match the changes in the metal salt solution entering the reactor (nickel content decreases and cobalt and manganese content increases), a positive electrode precursor material with a multilayer structure with decreasing nickel content and increasing cobalt and manganese content from the inside out is synthesized.

[0013] On the one hand, the positive electrode precursor material provided by the present invention presents a concentration gradient structure, the core is a densely packed nickel-rich material with high capacity, and the content of nickel element gradually decreases from the core to the outer surface, and the content of cobalt element and manganese element gradually increases, which is conducive to improving the tap density and structural stability of the positive electrode material. On the other hand, compared with the positive electrode precursor material with a single-layer structure, the positive electrode precursor material with a multilayer structure provided by the present invention has a larger specific surface area per unit volume and more interfaces, thereby improving the cycle stability of the prepared positive electrode material. Therefore, the positive electrode material prepared by the method provided by the present invention exhibits excellent cycle performance and rate performance.

[0014] Preferably, in step S1, the first mixed metal salt solution includes nickel, cobalt and manganese.

[0015] Preferably, in the first mixed metal salt solution in step S1, the molar ratio of the nickel element, the cobalt element and the manganese element is (90.8-91):(4.5-4.7):(4.45-4.55), for example, it can be 90.8:4.65:4.55, 90.85:4.6:4.55, 90.9:4.55:4.55, 90.9:4.65:4.45, 91:4.5:4.5 or 91:4.55:4.45, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0016] Preferably, the total concentration of all metal ions in the first mixed metal salt solution in step S1 is 1.8 mol / L-2.2 mol / L, for example, it can be 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L or 2.2 mol / L, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0017] Preferably, the flow rate of the first mixed metal salt solution in step S1 is 380L / h-420L / h, for example, it can be 380L / h, 390L / h, 400L / h, 410L / h or 420L / h, etc., and is not limited to the listed values. Other unlisted values within this numerical range are also applicable.

[0018] Preferably, the flow rate of the first precipitant solution in step S1 is 145 L / h-149 L / h, for example, it can be 145 L / h, 146 L / h, 147 L / h, 148 L / h or 149 L / h, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0019] Preferably, the flow rate of the first complexing agent solution in step S1 is 27 L / h-33 L / h, for example, it can be 27 L / h, 28 L / h, 29 L / h, 30 L / h, 31 L / h, 32 L / h or 33 L / h, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0020] Preferably, the pH value of the base solution in step S1 is 11.5-11.6, for example, it can be 11.5, 11.52, 11.55, 11.58 or 11.6, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0021] Preferably, the concentration of ammonia in the base liquid in step S1 is 6.5 g / L-7.0 g / L, for example, it can be 6.5 g / L, 6.6 g / L, 6.7 g / L, 6.8 g / L, 6.9 g / L or 7.0 g / L, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0022] Preferably, the temperature of the base liquid in step S1 is 55°C-65°C, for example, it can be 55°C, 58°C, 60°C, 62°C or 65°C, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0023] Preferably, the pH value of the first-stage coprecipitation reaction in step S1 is 11.0-11.5, preferably 11.25-11.35, for example, it can be 11.0, 11.1, 11.2, 11.25, 11.3, 11.35, 11.4 or 11.5, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0024] Preferably, the concentration of ammonia in the first-stage coprecipitation reaction in step S1 is 7.0 g / L-7.5 g / L, preferably 7.2 g / L-7.4 g / L, for example, it can be 7.0 g / L, 7.1 g / L, 7.2 g / L, 7.3 g / L, 7.4 g / L or 7.5 g / L, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0025] Preferably, the time of the first-stage coprecipitation reaction in step S1 is 15h-17h, for example, it can be 15h, 15.5h, 16h, 16.5h or 17h, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0026] Preferably, the stirring rate of the first-stage coprecipitation reaction in step S1 is 180 rpm-220 rpm, for example, it can be 180 rpm, 190 rpm, 200 rpm, 210 rpm or 220 rpm, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0027] Preferably, in step S2, the first target particle size is 5.7 μm-6.0 μm, for example, it can be 5.7 μm, 5.72 μm, 5.75 μm, 5.78 μm, 5.8 μm, 5.82 μm, 5.85 μm, 5.88 μm, 5.9 μm, 5.92 μm, 5.95 μm, 5.98 μm or 6.0 μm, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0028] It should be noted that the first target particle size specifically refers to the median particle size D50 of the first precursor material.

[0029] In the present invention, the target particle size of the first precursor material is adjusted to increase the tap density of the positive electrode precursor material. If a first precursor material with a larger particle size is used, the above effect cannot be achieved.

[0030] Preferably, the flow rate of the first mixed metal salt solution in step S2 is 180 L / h-220 L / h, for example, it can be 180 L / h, 190 L / h, 200 L / h, 210 L / h or 220 L / h, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0031] Preferably, in step S2, the second mixed metal salt solution includes nickel, cobalt, manganese and doping metal elements.

[0032] Preferably, the doping metal element includes aluminum.

[0033] Preferably, in the second mixed metal salt solution in step S2, the molar ratio of the nickel element, cobalt element, manganese element and doping metal element is (58.8-59):(37.5-37.7):(1.45-1.55):(1.9-2.1), for example, it can be 58.8:37.7:1.5:2, 58.8:37.65:1.55:2, 58.9:37.6:1.5:2, 58.9:37.55:1.55:2, 59:37.5:1.5:2 or 59:37.55:1.45:2, etc., not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0034] The present invention further introduces aluminum doping metal elements within a suitable content range to improve the thermal stability of the positive electrode precursor material.

[0035] Preferably, the total concentration of all metal ions in the second mixed metal salt solution in step S2 is 1.8 mol / L-2.2 mol / L, for example, it can be 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L or 2.2 mol / L, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0036] Preferably, the flow rate of the second mixed metal salt solution in step S2 is 180L / h-220L / h, for example, it can be 180L / h, 190L / h, 200L / h, 210L / h or 220L / h, etc., not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0037] Preferably, the flow rate of the second precipitant solution in step S2 is 140 L / h-150 L / h, for example, it can be 140 L / h, 141 L / h, 142 L / h, 143 L / h, 144 L / h, 145 L / h, 146 L / h, 147 L / h, 148 L / h, 149 L / h or 150 L / h, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0038] Preferably, the flow rate of the second complexing agent solution in step S2 is 27 L / h-33 L / h, for example, it can be 27 L / h, 28 L / h, 29 L / h, 30 L / h, 31 L / h, 32 L / h or 33 L / h, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0039] Preferably, the pH value of the second-stage coprecipitation reaction in step S2 is 10.5-10.8, preferably 10.6-10.7, for example, it can be 10.5, 10.55, 10.6, 10.65, 10.7, 10.75 or 10.8, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0040] Preferably, the concentration of ammonia in the second-stage coprecipitation reaction in step S2 is 7.0 g / L-8.0 g / L, preferably 7.6 g / L-7.7 g / L, for example, it can be 7.0 g / L, 7.2 g / L, 7.5 g / L, 7.6 g / L, 7.7 g / L, 7.8 g / L or 8.0 g / L, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0041] Preferably, the time of the second-stage coprecipitation reaction in step S2 is 3h-5h, for example, 3h, 3.5h, 4h, 4.5h or 5h, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0042] Preferably, the stirring rate of the second-stage co-precipitation reaction in step S2 is 110 rpm-130 rpm, for example, it can be 110 rpm, 115 rpm, 120 rpm, 125 rpm or 130 rpm, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0043] Preferably, in step S3, the second target particle size is 8.7 μm-9.0 μm, for example, it can be 8.7 μm, 8.72 μm, 8.75 μm, 8.78 μm, 8.8 μm, 8.82 μm, 8.85 μm, 8.88 μm, 8.9 μm, 8.92 μm, 8.95 μm, 8.98 μm or 9.0 μm, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0044] It should be noted that the second target particle size specifically refers to the median particle size D50 of the second precursor material.

[0045] In the present invention, the target particle size of the second precursor material is adjusted to increase the specific surface area of the positive electrode precursor material. If a second precursor material with a larger particle size is used, the above technical effect cannot be achieved.

[0046] Preferably, the flow rate of the second mixed metal salt solution in step S3 is 380L / h-420L / h, for example, it can be 380L / h, 390L / h, 400L / h, 410L / h or 420L / h, etc., and is not limited to the listed values. Other unlisted values within this numerical range are also applicable.

[0047] Preferably, the flow rate of the third precipitant solution in step S3 is 140 L / h-150 L / h, for example, it can be 140 L / h, 141 L / h, 142 L / h, 143 L / h, 144 L / h, 145 L / h, 146 L / h, 147 L / h, 148 L / h, 149 L / h or 150 L / h, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0048] Preferably, the flow rate of the third complexing agent solution in step S3 is 27 L / h-33 L / h, for example, it can be 27 L / h, 28 L / h, 29 L / h, 30 L / h, 31 L / h, 32 L / h or 33 L / h, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0049] Preferably, the pH value of the third stage coprecipitation reaction in step S3 is 10.5-10.8, preferably 10.6-10.7, for example, it can be 10.5, 10.55, 10.6, 10.65, 10.7, 10.75 or 10.8, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0050] Preferably, the concentration of ammonia in the third stage coprecipitation reaction in step S3 is 7.0 g / L-8.0 g / L, preferably 7.6 g / L-7.7 g / L, for example, it can be 7.0 g / L, 7.2 g / L, 7.5 g / L, 7.6 g / L, 7.7 g / L, 7.8 g / L or 8.0 g / L, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0051] Preferably, the time of the third stage coprecipitation reaction in step S3 is 24h-26h, for example, it can be 24h, 24.5h, 25h, 25.5h or 26h, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0052] Preferably, the stirring rate of the third stage coprecipitation reaction in step S3 is 110 rpm-130 rpm, for example, it can be 110 rpm, 115 rpm, 120 rpm, 125 rpm or 130 rpm, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0053] Preferably, the third target particle size in step S3 is 13.7 μm-14.0 μm, for example, it can be 13.7 μm, 13.72 μm, 13.75 μm, 13.78 μm, 13.8 μm, 13.82 μm, 13.85 μm, 13.88 μm, 13.9 μm, 13.92 μm, 13.95 μm, 13.98 μm or 14.0 μm, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0054] It should be noted that the third target particle size specifically refers to the median particle size D50 of the particles.

[0055] Preferably, the step S3 further includes an aging treatment after the average particle size of the particles reaches the third target particle size.

[0056] Preferably, the aging treatment time is 1 hour to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0057] Preferably, the temperatures of the first-stage co-precipitation reaction, the second-stage co-precipitation reaction and the third-stage co-precipitation reaction are the same, which are all 55°C-65°C, for example, 55°C, 58°C, 60°C, 62°C or 65°C, etc., are not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0058] In the present invention, the pH values of the first stage co-precipitation reaction, the second stage co-precipitation reaction, and the third stage co-precipitation reaction are controlled to an appropriate range, thereby preparing a positive electrode precursor material with uniform particle size and good consistency. If the above-mentioned different stages of co-precipitation reaction are carried out at a lower pH value, the surface defects of the particles will increase accordingly; if the above-mentioned different stages of co-precipitation reaction are carried out at a higher pH value, nucleation will be too rapid, thereby affecting the tap density and cycle performance of the positive electrode precursor material.

[0059] In the present invention, the present invention controls the concentration of ammonia in the first stage coprecipitation reaction, the second stage coprecipitation reaction, and the third stage coprecipitation reaction respectively, so that the reaction can be more complete, and it is beneficial to regulate the morphology of the positive electrode precursor material so that it has a larger specific surface area. If the concentration of ammonia in the above-mentioned different stages of the coprecipitation reaction is low, the coprecipitation reaction is incomplete; if the concentration of ammonia in the above-mentioned different stages of the coprecipitation reaction is high, it will inhibit the further increase of crystal particles, thereby reducing the specific surface area of the positive electrode precursor material.

[0060] In the present invention, the reaction time of the first stage co-precipitation reaction, the second stage co-precipitation reaction, and the third stage co-precipitation reaction is controlled within a specific range to obtain a cathode precursor material of an appropriate size. If the reaction time of the above-mentioned different stages of co-precipitation reaction is insufficient, the size of the cathode precursor material particles will not meet the standard; if the reaction time of the above-mentioned different stages of co-precipitation reaction is long, the production cost will be increased and other impurities may be introduced.

[0061] In the present invention, the stirring rates of the first, second, and third stage coprecipitation reactions are controlled within specific ranges to obtain a uniform and regular cathode precursor material. If the stirring rates of the coprecipitation reactions at different stages are low, uneven mixing of different particles may occur, thereby forming irregular particles. If the stirring rates of the coprecipitation reactions at different stages are high, the multilayer structure of the cathode precursor material may be destroyed.

[0062] In summary, the present invention achieves the following technical effects by regulating the specific parameters of the coprecipitation reaction at different stages:

[0063] (1) The first stage of coprecipitation reaction (forming the inner core layer): through high pH value (11.0-11.5) and low ammonia concentration (7.0g / L-7.5g / L), a dense micron-sized inner core (D 50 =5.7μm-6.0μm), thereby increasing the tap density of the positive electrode precursor material;

[0064] (2) The second stage of coprecipitation reaction (forming a transition layer): by lowering the pH value (10.5-10.8) and increasing the ammonia concentration (7.0 g / L-8.0 g / L), a porous transition layer (D 50 =8.7 μm-9.0 μm), thereby increasing the specific surface area of the positive electrode precursor material;

[0065] (3) The third stage of coprecipitation reaction (shell formation): by maintaining low pH and high ammonia concentration, the reaction time is prolonged (24h-26h) to form an ultra-thin shell (D 50 =13.7μm-14.0μm), thereby optimizing the cycle stability of the prepared positive electrode material.

[0066] In a second aspect, the present invention provides a positive electrode precursor material with a multi-layer structure, wherein the positive electrode precursor material with a multi-layer structure is prepared by the method for preparing the positive electrode precursor material with a multi-layer structure as described in the first aspect.

[0067] Preferably, the positive electrode precursor material with a multilayer structure includes a core layer, a transition layer and an outer shell layer from the inside to the outside, the molar ratio of nickel element, cobalt element and manganese element in the core layer is 0.909:0.046:0.045, and the molar ratio of nickel element, cobalt element, manganese element and doping metal element in the outer shell layer is 0.589:0.376:0.015:0.020.

[0068] In a third aspect, the present invention provides a positive electrode material, which is prepared from the positive electrode precursor material with a multilayer structure as described in the second aspect.

[0069] In the present invention, the method for preparing the positive electrode material exemplarily includes mixing the positive electrode precursor material with a multilayer structure as described in the second aspect with a lithium source, and sintering the mixture to obtain the positive electrode material.

[0070] In a fourth aspect, the present invention provides an application of the positive electrode material as described in the third aspect, wherein the positive electrode material is used for preparing a secondary battery.

[0071] Since the positive electrode material can inherit the structural characteristics of the precursor material, the positive electrode precursor material with a multilayer structure provided by the present invention can better exert the energy density and cycle stability of the nickel-rich material.

[0072] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] The present invention provides a method for preparing a cathode precursor material with a multilayer structure. By controlling the pH value of the coprecipitation reaction at different stages and the changes in ammonia concentration to match the changes in the metal salt solution entering the reactor (nickel content decreases and cobalt and manganese content increases), a cathode precursor material with a multilayer structure in which the nickel content decreases and the cobalt and manganese content increases from the inside out is synthesized.

[0075] On the one hand, the positive electrode precursor material provided by the present invention presents a concentration gradient structure, the core is a densely packed nickel-rich material with high capacity, and the content of nickel element gradually decreases from the core to the outer surface, and the content of cobalt element and manganese element gradually increases, which is conducive to improving the tap density and structural stability of the positive electrode material. On the other hand, compared with the positive electrode precursor material with a single-layer structure, the positive electrode precursor material with a multilayer structure provided by the present invention has a larger specific surface area per unit volume and more interfaces, thereby improving the cycle stability of the prepared positive electrode material. Therefore, the positive electrode material prepared by the method provided by the present invention exhibits excellent cycle performance and rate performance. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0077] Example 1

[0078] This embodiment provides a positive electrode precursor material with a multilayer structure and a preparation method thereof. The positive electrode precursor material with a multilayer structure includes, from the inside to the outside, an inner core layer, a transition layer, and an outer shell layer. The molar ratio of nickel, cobalt, and manganese in the inner core layer is 0.909:0.046:0.045, and the molar ratio of nickel, cobalt, manganese, and aluminum doping element in the outer shell layer is 0.589:0.376:0.015:0.020. The preparation method includes the following steps:

[0079] S1. Add 25 L of pure water, 10 mol / L sodium hydroxide solution, and 10 mol / L ammonia solution as the reaction base solution to a 100 L reactor. Control the initial pH value of the reaction base solution to 11.55, the ammonia concentration to 6.8 g / L, and the temperature to 60°C. A nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L were simultaneously introduced into a reactor containing the above-mentioned reaction base liquid to carry out a first-stage coprecipitation reaction, and the feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution was controlled to be 400 L / h, the feed flow rate of the sodium hydroxide solution was 147 L / h, and the feed flow rate of the ammonia solution was 30 L / h. The stirring rate of the reactor was set to 200 rpm, the reaction temperature was 60° C., the reaction time was 16 h, the pH value was 11.25, and the ammonia concentration was 7.2 g / L to obtain a first precursor material, wherein the molar ratio of nickel element, cobalt element and manganese element in the nickel-cobalt-manganese ternary mixed salt solution was 90.9:4.6:4.5;

[0080] S2. After the median particle size D50 of the first precursor material reaches the target particle size of 5.8 μm, a nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continuously introduced into the reactor to carry out the second stage of coprecipitation reaction. The feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution is controlled to be 200 L / h. The feed flow rate of the aluminum quaternary mixed salt solution is 200 L / h, the feed flow rate of the sodium hydroxide solution is 145 L / h, and the feed flow rate of the ammonia solution is 30 L / h. The stirring rate of the reactor is set to 120 rpm, the reaction temperature is 60° C., the reaction time is 4 hours, the pH value is 10.7, and the ammonia concentration is 7.7 g / L to obtain a second precursor material, wherein the molar ratio of nickel element, cobalt element, manganese element and aluminum doping metal element in the second mixed metal salt solution is 58.9:37.6:1.5:2;

[0081] S3. After the median particle size D50 of the second precursor material reaches the target particle size of 8.8 μm, the injection of the nickel-cobalt-manganese ternary mixed salt solution is stopped, and a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continued to be introduced into the reactor in parallel to carry out the third stage of coprecipitation reaction. The feed rate of the nickel-cobalt-manganese-aluminum quaternary mixed salt solution is controlled to 400 L / h. The feed flow rate of sodium hydroxide solution is 145 L / h, the feed flow rate of ammonia solution is 30 L / h, the stirring rate of the reactor is set to 120 rpm, the reaction temperature is 60 ° C, the reaction time is 25 h, the pH value is 10.7, and the ammonia concentration is 7.7 g / L. After the median particle size D50 of the particles reaches the target particle size of 13.8 μm, it is subsequently aged for 2 h, alkali washed and water washed, and dried to obtain the positive electrode precursor material with a multilayer structure.

[0082] Example 2

[0083] This embodiment provides a positive electrode precursor material with a multilayer structure and a preparation method thereof. The positive electrode precursor material with a multilayer structure includes, from the inside to the outside, an inner core layer, a transition layer, and an outer shell layer. The molar ratio of nickel, cobalt, and manganese in the inner core layer is 0.909:0.046:0.045, and the molar ratio of nickel, cobalt, manganese, and aluminum doping element in the outer shell layer is 0.589:0.376:0.015:0.020. The preparation method includes the following steps:

[0084] S1. Add 25 L of pure water, 10 mol / L sodium hydroxide solution, and 10 mol / L ammonia solution as the reaction base solution to a 100 L reactor. Control the initial pH value of the reaction base solution to 11.55, the ammonia concentration to 6.7 g / L, and the temperature to 60°C. A nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L were simultaneously introduced into a reactor containing the above-mentioned reaction base liquid to carry out a first-stage coprecipitation reaction, and the feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution was controlled to be 400 L / h, the feed flow rate of the sodium hydroxide solution was 147 L / h, and the feed flow rate of the ammonia solution was 30 L / h. The stirring rate of the reactor was set to 200 rpm, the reaction temperature was 60° C., the reaction time was 16 h, the pH value was 11.35, and the ammonia concentration was 7.4 g / L to obtain a first precursor material, wherein the molar ratio of nickel element, cobalt element and manganese element in the nickel-cobalt-manganese ternary mixed salt solution was 90.9:4.6:4.5;

[0085] S2. After the median particle size D50 of the first precursor material reaches the target particle size of 5.7 μm, a nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continuously introduced into the reactor to carry out the second stage of coprecipitation reaction. The feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution is controlled to be 200 L / h. The feed flow rate of the aluminum quaternary mixed salt solution is 200 L / h, the feed flow rate of the sodium hydroxide solution is 145 L / h, and the feed flow rate of the ammonia solution is 30 L / h. The stirring rate of the reactor is set to 120 rpm, the reaction temperature is 60° C., the reaction time is 4 hours, the pH value is 10.65, and the ammonia concentration is 7.6 g / L to obtain a second precursor material, wherein the molar ratio of nickel element, cobalt element, manganese element and aluminum doping metal element in the second mixed metal salt solution is 58.9:37.6:1.5:2;

[0086] S3. After the median particle size D50 of the second precursor material reaches the target particle size of 8.9 μm, the injection of the nickel-cobalt-manganese ternary mixed salt solution is stopped, and a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continued to be introduced into the reactor in parallel to carry out the third stage of coprecipitation reaction. The feed rate of the nickel-cobalt-manganese-aluminum quaternary mixed salt solution is controlled to 400 L / h. The feed flow rate of sodium hydroxide solution is 145 L / h, the feed flow rate of ammonia solution is 30 L / h, the stirring rate of the reactor is set to 120 rpm, the reaction temperature is 60 ° C, the reaction time is 25 h, the pH value is 10.7, and the ammonia concentration is 7.6 g / L. After the median particle size D50 of the particles reaches the target particle size of 13.9 μm, it is subsequently aged for 2 h, alkali washed and water washed, and dried to obtain the positive electrode precursor material with a multilayer structure.

[0087] Example 3

[0088] This embodiment provides a positive electrode precursor material with a multilayer structure and a preparation method thereof. The positive electrode precursor material with a multilayer structure includes, from the inside to the outside, an inner core layer, a transition layer, and an outer shell layer. The molar ratio of nickel, cobalt, and manganese in the inner core layer is 0.909:0.046:0.045, and the molar ratio of nickel, cobalt, manganese, and aluminum doping element in the outer shell layer is 0.589:0.376:0.015:0.020. The preparation method includes the following steps:

[0089] S1. Add 25 L of pure water, 10 mol / L sodium hydroxide solution, and 10 mol / L ammonia solution as the reaction base solution to a 100 L reactor. Control the initial pH value of the reaction base solution to 11.5, the ammonia concentration to 6.5 g / L, and the temperature to 55°C. A nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L were simultaneously introduced into a reactor containing the above-mentioned reaction base liquid to carry out a first-stage coprecipitation reaction, and the feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution was controlled to be 380 L / h, the feed flow rate of the sodium hydroxide solution was 145 L / h, and the feed flow rate of the ammonia solution was 27 L / h. The stirring rate of the reactor was set to 180 rpm, the reaction temperature was 55° C., the reaction time was 15 h, the pH value was 11.0, and the ammonia concentration was 7.0 g / L to obtain a first precursor material, wherein the molar ratio of nickel element, cobalt element and manganese element in the nickel-cobalt-manganese ternary mixed salt solution was 90.8:4.7:4.5;

[0090] S2. After the median particle size D50 of the first precursor material reaches the target particle size of 5.7 μm, a nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continuously introduced into the reactor to carry out the second stage of coprecipitation reaction. The feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution is controlled to be 180 L / h. The feed flow rate of the aluminum quaternary mixed salt solution is 180 L / h, the feed flow rate of the sodium hydroxide solution is 140 L / h, and the feed flow rate of the ammonia solution is 27 L / h. The stirring rate of the reactor is set to 110 rpm, the reaction temperature is 55° C., the reaction time is 3 hours, the pH value is 10.5, and the ammonia concentration is 7.0 g / L to obtain a second precursor material, wherein the molar ratio of nickel element, cobalt element, manganese element and aluminum doping metal element in the second mixed metal salt solution is 58.8:37.7:1.5:2;

[0091] S3. After the median particle size D50 of the second precursor material reaches the target particle size of 8.7 μm, the injection of the nickel-cobalt-manganese ternary mixed salt solution is stopped, and a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continued to be introduced into the reactor in parallel to carry out the third stage of coprecipitation reaction. The feed rate of the nickel-cobalt-manganese-aluminum quaternary mixed salt solution is controlled to 380 L / h. The feed flow rate of sodium hydroxide solution is 140 L / h, the feed flow rate of ammonia solution is 27 L / h, the stirring rate of the reactor is set to 110 rpm, the reaction temperature is 55 ° C, the reaction time is 24 h, the pH value is 10.5, and the ammonia concentration is 7.0 g / L. After the median particle size D50 of the particles reaches the target particle size of 13.7 μm, it is subsequently aged for 2 h, alkali washed and water washed, and dried to obtain the positive electrode precursor material with a multilayer structure.

[0092] Example 4

[0093] This embodiment provides a positive electrode precursor material with a multilayer structure and a preparation method thereof. The positive electrode precursor material with a multilayer structure includes, from the inside to the outside, an inner core layer, a transition layer, and an outer shell layer. The molar ratio of nickel, cobalt, and manganese in the inner core layer is 0.909:0.046:0.045, and the molar ratio of nickel, cobalt, manganese, and aluminum doping element in the outer shell layer is 0.589:0.376:0.015:0.020. The preparation method includes the following steps:

[0094] S1. Add 25 L of pure water, 10 mol / L sodium hydroxide solution, and 10 mol / L ammonia solution as the reaction base solution to a 100 L reactor. Control the initial pH value of the reaction base solution to 11.6, the ammonia concentration to 7.0 g / L, and the temperature to 65°C. A nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L were simultaneously introduced into a reactor containing the above-mentioned reaction base liquid to carry out a first-stage coprecipitation reaction, and the feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution was controlled to be 420 L / h, the feed flow rate of the sodium hydroxide solution was 149 L / h, and the feed flow rate of the ammonia solution was 33 L / h. The stirring rate of the reactor was set to 220 rpm, the reaction temperature was 65° C., the reaction time was 17 h, the pH value was 11.5, and the ammonia concentration was 7.5 g / L to obtain a first precursor material, wherein the molar ratio of nickel element, cobalt element and manganese element in the nickel-cobalt-manganese ternary mixed salt solution was 91:4.55:4.45;

[0095] S2. After the median particle size D50 of the first precursor material reaches the target particle size of 6.0 μm, a nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continuously introduced into the reactor to carry out the second stage of coprecipitation reaction. The feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution is controlled to be 220 L / h, and the nickel-cobalt-manganese The feed flow rate of the aluminum quaternary mixed salt solution is 220 L / h, the feed flow rate of the sodium hydroxide solution is 150 L / h, and the feed flow rate of the ammonia solution is 33 L / h. The stirring rate of the reactor is set to 130 rpm, the reaction temperature is 65° C., the reaction time is 5 hours, the pH value is 10.8, and the ammonia concentration is 8.0 g / L to obtain a second precursor material, wherein the molar ratio of nickel element, cobalt element, manganese element and aluminum doping metal element in the second mixed metal salt solution is 59:37.55:1.45:2;

[0096] S3. After the median particle size D50 of the second precursor material reaches the target particle size of 9.0 μm, the injection of the nickel-cobalt-manganese ternary mixed salt solution is stopped, and a nickel-cobalt-manganese-aluminum quaternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L are continued to be introduced into the reactor in parallel to carry out the third stage of coprecipitation reaction. The feed rate of the nickel-cobalt-manganese-aluminum quaternary mixed salt solution is controlled to 420 L / h. The feed flow rate of sodium hydroxide solution is 150 L / h, the feed flow rate of ammonia solution is 33 L / h, the stirring rate of the reactor is set to 130 rpm, the reaction temperature is 65 ° C, the reaction time is 26 h, the pH value is 10.8, and the ammonia concentration is 8.0 g / L. After the median particle size D50 of the particles reaches the target particle size of 14.0 μm, it is subsequently aged for 2 h, alkali washed and water washed, and dried to obtain the positive electrode precursor material with a multilayer structure.

[0097] Example 5

[0098] The difference between this embodiment and embodiment 1 is that the concentration of ammonia in the base liquid in step S1 is 5.0 g / L, and the rest is the same as embodiment 1.

[0099] Example 6

[0100] The difference between this embodiment and embodiment 1 is that the pH value of the first stage coprecipitation reaction in step S1 is 10.8, and the rest is the same as embodiment 1.

[0101] Example 7

[0102] The difference between this embodiment and embodiment 1 is that the pH value of the first stage coprecipitation reaction in step S1 is 11.8, and the rest is the same as embodiment 1.

[0103] Example 8

[0104] The difference between this embodiment and embodiment 1 is that the concentration of ammonia in the first stage co-precipitation reaction in step S1 is 5.0 g / L, and the rest is the same as embodiment 1.

[0105] Example 9

[0106] The difference between this embodiment and embodiment 1 is that the target particle size of the median particle size D50 of the first precursor material in step S2 is 3.0 μm, and the rest is the same as embodiment 1.

[0107] Example 10

[0108] The difference between this embodiment and embodiment 1 is that the target particle size of the median particle size D50 of the first precursor material in step S2 is 10.0 μm, and the rest is the same as embodiment 1.

[0109] Example 11

[0110] The difference between this embodiment and embodiment 1 is that the concentration of ammonia in the second stage co-precipitation reaction in step S2 and the third stage co-precipitation reaction in step S3 are both 8.5 g / L, and the rest are the same as in embodiment 1.

[0111] Example 12

[0112] The difference between this embodiment and embodiment 1 is that the target particle size of the median particle size D50 of the second precursor material in step S3 is 6.0 μm, and the rest is the same as embodiment 1.

[0113] Example 13

[0114] The difference between this embodiment and embodiment 1 is that the target particle size of the median particle size D50 of the second precursor material in step S3 is 12.0 μm, and the rest is the same as embodiment 1.

[0115] Example 14

[0116] The difference between this embodiment and embodiment 1 is that the time of the first stage coprecipitation reaction in step S1 is 12 hours, and the rest is the same as embodiment 1.

[0117] Example 15

[0118] The difference between this embodiment and embodiment 1 is that the time of the third stage co-precipitation reaction in step S3 is 20 hours, and the other aspects are the same as those in embodiment 1.

[0119] Example 16

[0120] The difference between this embodiment and embodiment 1 is that the stirring rate of the first stage coprecipitation reaction in step S1 is 150 rpm, and the rest is the same as embodiment 1.

[0121] Comparative Example 1

[0122] This comparative example provides a positive electrode precursor material with a single-layer structure, which includes the following steps:

[0123] 25 L of pure water, 10 mol / L sodium hydroxide solution and 10 mol / L ammonia solution were added to a 100 L reactor as reaction base liquids. The initial pH value of the reaction base liquid was controlled to be 11.55, the ammonia concentration was 6.8 g / L and the temperature was controlled to be 60°C. A nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L were simultaneously introduced into a reactor containing the above-mentioned reaction base liquid to carry out a coprecipitation reaction. The feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution was controlled to be 400 L / h, the feed flow rate of the sodium hydroxide solution was 147 L / h, and the feed flow rate of the ammonia solution was 30 L / h. The stirring rate of the reactor was set to 200 rpm, the reaction temperature was 60°C, the reaction time was 16 h, the pH value was 11.2, and the ammonia concentration was 7.2 g / L. After the median particle size D50 of the particles reached the target particle size of 13.8 μm, the particles were subsequently aged for 2 h, washed with alkali, and washed with water. After drying, a positive electrode precursor material with a single-layer structure was obtained, wherein the molar ratio of nickel element, cobalt element and manganese element in the nickel-cobalt-manganese ternary mixed salt solution was 90.9:4.6:4.5.

[0124] Comparative Example 2

[0125] This comparative example provides a positive electrode precursor material that does not contain aluminum, which includes the following steps:

[0126] S1. Add 25 L of pure water, 10 mol / L sodium hydroxide solution, and 10 mol / L ammonia solution as the reaction base solution to a 100 L reactor. Control the initial pH value of the reaction base solution to 11.55, the ammonia concentration to 6.8 g / L, and the temperature to 60°C. A nickel-cobalt-manganese ternary mixed salt solution with a total metal ion concentration of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L were simultaneously introduced into a reactor containing the above-mentioned reaction base liquid to carry out a first-stage coprecipitation reaction, and the feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution was controlled to be 400 L / h, the feed flow rate of the sodium hydroxide solution was 147 L / h, and the feed flow rate of the ammonia solution was 30 L / h. The stirring rate of the reactor was set to 200 rpm, the reaction temperature was 60° C., the reaction time was 16 h, the pH value was 11.2, and the ammonia concentration was 7.2 g / L to obtain a first precursor material, wherein the molar ratio of nickel element, cobalt element and manganese element in the nickel-cobalt-manganese ternary mixed salt solution was 90.9:4.6:4.5;

[0127] S2. After the median particle size D50 of the first precursor material reaches the target particle size of 5.8 μm, continue to flow into the reactor in parallel a nickel-cobalt-manganese ternary mixed salt solution with a total concentration of all metal ions of 2 mol / L, a sodium hydroxide solution with a concentration of 10 mol / L, and an ammonia solution with a concentration of 10 mol / L to carry out a second stage coprecipitation reaction, control the feed flow rate of the nickel-cobalt-manganese ternary mixed salt solution to 200 L / h, the feed flow rate of the sodium hydroxide solution to 145 L / h, and the feed flow rate of the ammonia solution to 30 L / h, set the stirring rate of the reactor to 120 rpm, the reaction temperature to 60°C, the reaction time to 4 h, the pH value to 10.7, and the ammonia concentration to 7.5 g / L. After the median particle size D50 of the particles reaches the target particle size of 13.8 μm, it is subsequently aged for 2 h, alkali washed, and washed with water, and dried to obtain a positive electrode precursor material that does not contain aluminum elements.

[0128] Comparative Example 3

[0129] The difference between this comparative example and Example 1 is that the feed flow rate of the ammonia solution is adjusted so that the ammonia concentration in the first stage coprecipitation reaction process in step S1 is 8.0 g / L, and the other conditions are the same as those in Example 1.

[0130] Test conditions

[0131] (1) The positive electrode precursor materials provided in the above embodiments and comparative examples were tested for their tap density using a tap density tester, and their specific surface area using a specific surface area tester.

[0132] (2) The positive electrode precursor materials provided in the above embodiments and comparative examples were sintered with lithium hydroxide, and the ratio of the total molar amount of nickel, cobalt and manganese in the positive electrode precursor materials to the molar amount of lithium hydroxide was controlled to be 1:1.2, wherein the sintering heating rate was 4°C / min, the target temperature was 600°C, and the holding time was 12h to obtain a positive electrode material; the above positive electrode material was mixed with conductive carbon black and polyvinylidene fluoride binder in a mass ratio of 8:1:1, and then N-methylpyrrolidone solvent was added to prepare a positive electrode slurry, and the positive electrode was The slurry is scraped onto aluminum foil, and after subsequent drying and rolling, it is cut into discs with a diameter of 12 mm as the positive electrode sheet, the metal lithium sheet as the negative electrode sheet, and a polypropylene separator to separate the positive and negative electrodes. The solute of the electrolyte is lithium hexafluorophosphate with a concentration of 1 mol / L, and the solvent is a mixture of ethylene carbonate, dimethyl carbonate and diethyl carbonate with a volume ratio of 1:1:1. The negative electrode shell, negative electrode sheet, electrolyte, separator, electrolyte, positive electrode sheet, current collector and positive electrode shell are stacked and pressed in this order to assemble into a button-type lithium-ion battery.

[0133] The prepared button-type lithium-ion battery was subjected to electrochemical performance testing at a test voltage of 3.0V-4.3V. The initial discharge specific capacity was tested at a 0.1C rate, and the capacity retention rate after 200 charge and discharge cycles of the button-type lithium-ion battery was tested at a 1C rate.

[0134] The test results are shown in Table 1:

[0135] Table 1

[0136]

[0137]

[0138] As can be seen from Table 1, compared with Comparative Examples 1-2, the preparation method of the positive electrode precursor material with a multilayer structure provided by Examples 1-4 of the present invention significantly improves the comprehensive performance of the material through multilayer structure design (nickel content gradient distribution + aluminum doping), and at the same time utilizes parameter optimization (pH, ammonia concentration and particle size control, etc.) during the preparation process to further improve the electrochemical performance of the prepared positive electrode material. Examples 5-16 and Comparative Example 3 show that any parameter deviation will lead to a decrease in the performance of the precursor material, verifying the necessity and innovation of the technical solution in the present invention.

[0139] Comparison of Example 1 with Examples 6 and 7 reveals that the present invention achieves a cathode precursor material having both high tap density and high specific surface area by regulating the pH value of the first-stage coprecipitation reaction to an appropriate range. Carrying out the coprecipitation reaction at a lower pH value results in an increase in particle surface defects; while carrying out the coprecipitation reaction at a higher pH value results in excessive nucleation, which in turn affects the tap density and cycle performance of the cathode precursor material.

[0140] Comparing Example 1, Example 5, Example 8, and Example 11, it can be seen that the present invention controls the concentration of ammonia in the coprecipitation reaction at different stages, so that the reaction can be more complete and is conducive to regulating the morphology of the positive electrode precursor material, so that it has a larger specific surface area. If the concentration of ammonia in the coprecipitation reaction at different stages is low, the coprecipitation reaction is incomplete; if the concentration of ammonia in the coprecipitation reaction at different stages is high, it will inhibit the further increase of crystal particles, thereby reducing the specific surface area of the positive electrode precursor material.

[0141] By comparing Example 1, Example 9-Example 10, and Example 12-Example 13, it can be seen that the present invention further optimizes the structure and composition of the positive electrode precursor material by regulating the target particle size of the particles in the co-precipitation reaction at different stages.

[0142] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection 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 those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a positive electrode precursor material with a multilayer structure, characterized in that: The preparation method comprises the following steps: S1. The first mixed metal salt solution, the first precipitant solution and the first complexing agent solution are passed into the reactor containing the bottom liquid, and the first stage coprecipitation reaction is performed to obtain a first precursor material; S2. After the average particle size of the first precursor material reaches the first target particle size, the first mixed metal salt solution, the second mixed metal salt solution, the second precipitant solution, and the second complexing agent solution are continued to be introduced into the reactor and the second stage coprecipitation reaction is performed to obtain a second precursor material; S3. After the average particle size of the second precursor material reaches the second target particle size, the injection of the first mixed metal salt solution is stopped, and the second mixed metal salt solution, the third precipitant solution and the third complexing agent solution are continued to be introduced into the reactor in parallel to perform a third stage coprecipitation reaction. After the average particle size of the particles reaches the third target particle size, the positive electrode precursor material having a multilayer structure is obtained; In which, the molar percentage of nickel element in the first mixed metal salt solution is higher than the molar percentage of nickel element in the second mixed metal salt solution, and the pH value of the first stage co-precipitation reaction is higher than the pH value of the second stage co-precipitation reaction and the third stage co-precipitation reaction, and the ammonia concentration in the first stage co-precipitation reaction is not higher than the ammonia concentration in the second stage co-precipitation reaction and the third stage co-precipitation reaction.

2. The preparation method according to claim 1, characterized in that In step S1, the first mixed metal salt solution includes nickel, cobalt and manganese; Preferably, in the first mixed metal salt solution in step S1, the molar ratio of the nickel element, the cobalt element and the manganese element is (90.8-91):(4.5-4.7):(4.45-4.55); Preferably, the total concentration of all metal ions in the first mixed metal salt solution in step S1 is 1.8 mol / L-2.2 mol / L; Preferably, in step S1, the flow rate of the first mixed metal salt solution is 380 L / h-420 L / h; Preferably, the flow rate of the first precipitant solution in step S1 is 145 L / h-149 L / h; Preferably, the flow rate of the first complexing agent solution in step S1 is 27 L / h-33 L / h; Preferably, the pH value of the base solution in step S1 is 11.5-11.6; Preferably, the concentration of ammonia in the base solution in step S1 is 6.5 g / L-7.0 g / L; Preferably, the temperature of the base solution in step S1 is 55°C-65°C; Preferably, the pH value of the first stage coprecipitation reaction in step S1 is 11.0-11.5, preferably 11.25-11.35; Preferably, the concentration of ammonia in the first stage coprecipitation reaction in step S1 is 7.0 g / L-7.5 g / L, preferably 7.2 g / L-7.4 g / L; Preferably, the time of the first stage coprecipitation reaction in step S1 is 15h-17h; Preferably, the stirring rate of the first stage co-precipitation reaction in step S1 is 180 rpm-220 rpm.

3. The preparation method according to claim 1 or 2, characterized in that In step S2, the first target particle size is 5.7 μm-6.0 μm; Preferably, in step S2, the flow rate of the first mixed metal salt solution is 180 L / h-220 L / h; Preferably, in step S2, the second mixed metal salt solution comprises nickel, cobalt, manganese and doping metal elements; Preferably, the doping metal element includes aluminum; Preferably, in the second mixed metal salt solution in step S2, the molar ratio of the nickel element, the cobalt element, the manganese element and the doping metal element is (58.8-59):(37.5-37.7):(1.45-1.55):(1.9-2.1); Preferably, the total concentration of all metal ions in the second mixed metal salt solution in step S2 is 1.8 mol / L-2.2 mol / L; Preferably, the flow rate of the second mixed metal salt solution in step S2 is 180 L / h-220 L / h; Preferably, the flow rate of the second precipitant solution in step S2 is 140 L / h-150 L / h; Preferably, the flow rate of the second complexing agent solution in step S2 is 27 L / h-33 L / h; Preferably, the pH value of the second stage co-precipitation reaction in step S2 is 10.5-10.8, preferably 10.6-10.7; Preferably, the concentration of ammonia in the second-stage coprecipitation reaction in step S2 is 7.0 g / L-8.0 g / L, preferably 7.6 g / L-7.7 g / L; Preferably, the time of the second stage coprecipitation reaction in step S2 is 3h-5h; Preferably, the stirring rate of the second-stage co-precipitation reaction in step S2 is 110 rpm-130 rpm.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step S3, the second target particle size is 8.7 μm-9.0 μm; Preferably, the flow rate of the second mixed metal salt solution in step S3 is 380 L / h-420 L / h; Preferably, the flow rate of the third precipitant solution in step S3 is 140 L / h-150 L / h; Preferably, the flow rate of the third complexing agent solution in step S3 is 27 L / h-33 L / h; Preferably, the pH value of the third stage coprecipitation reaction in step S3 is 10.5-10.8, preferably 10.6-10.7; Preferably, the concentration of ammonia in the third stage coprecipitation reaction in step S3 is 7.0 g / L-8.0 g / L, preferably 7.6 g / L-7.7 g / L; Preferably, the time of the third stage coprecipitation reaction in step S3 is 24h-26h; Preferably, the stirring rate of the third stage coprecipitation reaction in step S3 is 110 rpm-130 rpm; Preferably, the third target particle size in step S3 is 13.7 μm-14.0 μm.

5. The preparation method according to any one of claims 1 to 4, characterized in that After the average particle size of the particles reaches the third target particle size in step S3, an aging treatment is also included; Preferably, the aging treatment time is 1 hour to 3 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that The temperatures of the first stage co-precipitation reaction, the second stage co-precipitation reaction and the third stage co-precipitation reaction are the same, which is 55° C.-65° C.

7. A positive electrode precursor material having a multilayer structure, characterized in that: The positive electrode precursor material with a multi-layer structure is prepared by the method for preparing a positive electrode precursor material with a multi-layer structure according to any one of claims 1 to 6.

8. The positive electrode precursor material with a multilayer structure according to claim 7, characterized in that: The positive electrode precursor material with a multi-layer structure includes a core layer, a transition layer and an outer shell layer from the inside to the outside, the molar ratio of nickel element, cobalt element and manganese element in the core layer is 0.909:0.046:0.045, and the molar ratio of nickel element, cobalt element, manganese element and doping metal element in the outer shell layer is 0.589:0.376:0.015:0.

020.

9. A positive electrode material, characterized in that The positive electrode material is prepared from the positive electrode precursor material with a multilayer structure as claimed in claim 7 or 8.

10. Use of the positive electrode material according to claim 9, characterized in that: The positive electrode material is used for preparing a secondary battery.

Images