Shell-doped high-nickel ternary precursor as well as preparation method and application thereof

Abstract

The invention provides a shell-doped high-nickel ternary precursor and a preparation method and application thereof.The preparation method comprises the steps that a first mixed metal salt solution, a precipitator solution and a complexing agent solution are introduced into a first base solution, a first coprecipitation reaction is conducted, seed crystal slurry is obtained, solid-liquid separation, washing and drying are conducted on the seed crystal slurry, and a shell-doped high-nickel ternary precursor is obtained; preparing the seed crystal into a second base solution, and performing seed crystal activation treatment on the second base solution to obtain an activated base solution; and introducing the second mixed metal salt solution, the precipitator solution and the complexing agent solution into the activated base solution, and carrying out a second coprecipitation reaction to obtain the shell-doped high-nickel ternary precursor, the second mixed metal salt solution comprises doped metal ions. According to the preparation method disclosed by the invention, the undoped seed crystal is firstly prepared, the seed crystal is activated, the secondary coprecipitation reaction is continuously performed, and the doped shell layer is prepared on the surface of the seed crystal, so that the structural stability of the material can be improved while the capacity is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and relates to a shell-doped high-nickel ternary precursor and a preparation method and application thereof. BACKGROUND

[0002] The ultra-high nickel positive electrode material with a core-shell structure is widely used due to high capacity and high stability. Most of the existing core-shell structure precursors have the same material but different concentrations in the core and the shell. For example, the core has a high nickel concentration to achieve high capacity, and the shell has a high manganese concentration to improve the structural stability of the particles. This method is generally considered to be a compromise strategy for high capacity and structural stability. However, due to the reduction of the nickel concentration in the shell, the capacity of the obtained material will be slightly compensated. CN107359346A discloses a lithium battery positive electrode material modified multi-element precursor and a preparation method, which has a complex structure connected by two concentration gradient transition layers in the core, the intermediate layer and the shell. Although it has high capacity, it cannot reach the high capacity level that can be achieved by high-nickel precursors, and its structure contains six gradient layers to achieve cycle stability, which faces challenges in actual production.

[0003] Another existing modification method of the high-nickel ternary precursor is doping. Known doping materials such as Zr, Mg, W, Mo, Al, B, Cr, Ge, Sr or Y can improve the performance of the precursor material. This method also compensates for the capacity of the precursor material, but the proportion of the doping material must not be excessive, otherwise it will cause capacity decay. Another modification method is to use several elements (such as Al, Ti, Mg or Zr) known to effectively prevent the collapse of the precursor structure to prepare a surface coating, but the thickness of the surface coating needs to be controlled to obtain the best performance. Excessive surface coating sometimes affects the lithium ion charge-discharge kinetics, and the coating material blocks the lithium ion path, thereby slowing down the kinetic process.

[0004] Based on the above research, it is necessary to provide a preparation method of a high-nickel ternary precursor. The preparation method has a simple process, can be implemented on an industrial production scale using existing equipment, and the prepared product has high sphericity, regular particle size distribution, no cracking, and can balance the capacity and stability of the material. SUMMARY

[0005] The purpose of the present application is to provide a shell-doped high-nickel ternary precursor and a preparation method and application thereof. The preparation method first prepares an undoped seed crystal, activates the seed crystal, and then continues the second co-precipitation reaction to prepare a doped shell on the surface of the seed crystal, thereby improving the structural stability of the material while ensuring the capacity.

[0006] To achieve this application purpose, the following technical solutions are adopted in the present application:

[0007] In a first aspect, the present application provides a preparation method of a shell-doped high-nickel ternary precursor, comprising the following steps:

[0008] (1) introducing a first mixed metal salt solution, a precipitant solution and a complexing agent solution into a first bottom solution to perform a first co-precipitation reaction, to obtain a seed slurry, and performing solid-liquid separation, washing and drying on the seed slurry to obtain seed crystals, and preparing the seed crystals into a second bottom solution, and performing seed crystal activation treatment on the second bottom solution to obtain an activated bottom solution;

[0009] (2) introducing a second mixed metal salt solution, a precipitant solution and a complexing agent solution into the activated bottom solution of step (1) to perform a second co-precipitation reaction, to obtain the shell-doped high-nickel ternary precursor;

[0010] The second mixed metal salt solution comprises doped metal ions.

[0011] The present application first prepares seed crystals without doped elements, and then performs a second co-precipitation reaction guided by the seed crystals to prepare a doped shell layer on the surface of the seed crystals. Before the second co-precipitation reaction, the seed crystals are prepared into a second bottom solution, and seed crystal activation treatment is performed on the second bottom solution to increase the specific surface area and surface roughness of the seed crystals, and promote the co-precipitation of the second co-precipitation reaction product on the surface of the seed crystals. This not only improves the bonding strength of the inner core and the shell, but also improves the uniformity of the product.

[0012] In addition, the present application takes a high-nickel ternary precursor as a core part, and adds doped elements in the shell structure to maintain the structural stability of the precursor and act as a protective barrier for the core material, without causing excessive capacity loss. On the premise of not using excessive doped materials, the precursor material can obtain the maximum capacity and protect its structural stability. Specifically, the doped elements are substituted in the crystal lattice and segregated at the grain boundaries to inhibit cation mixing, can maintain the layered structure during the cycling process, prevent the formation of micro-cracks in the secondary particles, and also form an effective thin protective layer on the surface, thereby minimizing the blockage of the (lithium ion) channel.

[0013] Preferably, the seed crystal activation treatment of step (1) is performed under stirring.

[0014] Preferably, the seed crystal activation treatment of step (1) is performed in an oxygen-containing atmosphere.

[0015] Preferably, the temperature of the seed crystal activation treatment of step (1) is higher than the temperatures of the first co-precipitation reaction of step (1) and the second co-precipitation reaction of step (2).

[0016] Preferably, the oxygen content in the reaction atmosphere of the seed crystal activation treatment of step (1) is greater than the oxygen content in the reaction atmosphere of the first co-precipitation reaction of step (1) and the second co-precipitation reaction of step (2).

[0017] The seed crystal activation treatment of the present application is carried out under stirring in an oxygen-containing atmosphere and at a higher temperature than the first co-precipitation reaction and the second co-precipitation reaction, so as to achieve seed crystal activation; and the seed crystal activation treatment preferably simultaneously satisfies both high temperature and an oxygen-containing atmosphere, and the lack of either one will affect the seed crystal activation effect, thereby affecting the bonding strength between the core and the shell layer and the cycle performance of the battery.

[0018] Preferably, the time of the seed crystal activation treatment of step (1) is 1h-2h.

[0019] The time of the seed crystal activation treatment of the present application will affect the seed crystal activation effect, and if the activation time is too short, the seed crystal activation effect will be poor, and if the activation time is too long, the structure stability of the seed crystal will decrease.

[0020] Preferably, the temperature of the seed crystal activation treatment of step (1) is 55℃-65℃, for example, it can be 55℃, 57℃, 59℃, 61℃, 63℃ or 65℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0021] Preferably, the stirring rate of the seed crystal activation treatment of step (1) is 600rpm-700rpm, for example, it can be 600rpm, 625rpm, 650rpm, 675rpm or 700rpm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0022] Preferably, the seed crystal activation treatment of step (1) is carried out in oxygen and a protective gas.

[0023] Preferably, the volume ratio of the oxygen and the protective gas is (1-1.5):300, for example, it can be 1:300, 1.25:300 or 1.5:300, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0024] Preferably, the first co-precipitation reaction and the second co-precipitation reaction of step (1) are carried out in a protective gas.

[0025] Preferably, the protective gas comprises nitrogen.

[0026] Preferably, the temperature of the first co-precipitation reaction and the second co-precipitation reaction of step (1) is independently 50℃-65℃, for example, it can be 50℃, 55℃, 60℃ or 65℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0027] Preferably, the stirring rate of the first co-precipitation reaction and the second co-precipitation reaction of step (1) is independently 500 rpm-1000 rpm, for example, it can be 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0028] Preferably, in the system of the first co-precipitation reaction of step (1), the concentration of the complexing agent is in the range of 4 g / L-5 g / L, for example, it can be 4 g / L, 4.5 g / L or 5 g / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0029] Preferably, the first co-precipitation reaction of step (1) includes a nucleation reaction and a growth reaction performed in sequence, the pH of the nucleation reaction is in the range of 11-12, for example, it can be 11, 11.5 or 12, and the pH of the growth reaction is in the range of 10.5-11.5, for example, it can be 10.5, 11 or 11.5, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0030] Preferably, the particle size D50 of the particles obtained after the nucleation reaction is 1 μm-2 μm, for example, it can be 1 μm, 1.5 μm or 2 μm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] Preferably, the particle size D50 of the seed crystals of step (1) is 3.5 μm-4.5 μm, for example, it can be 3.5 μm, 3.75 μm, 4.0 μm, 4.25 μm or 4.5 μm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0032] Preferably, the pH of the first bottom solution of step (1) is 10.5-11.5, for example, it can be 10.5, 11 or 11.5, and the concentration of the complexing agent in the first bottom solution is in the range of 4 g / L-5 g / L, for example, it can be 4 g / L, 4.5 g / L or 5 g / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] Preferably, the concentration of the first mixed metal salt solution of step (1) is 80 g / L-150 g / L, for example, it can be 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0034] Preferably, in the first mixed metal salt solution of step (1), the molar ratio of nickel ions, cobalt ions and manganese ions is x:y:(1-x-y), wherein 0.8≤x≤0.93, for example, it can be 0.8, 0.85, 0.9 or 0.93, 0.05≤y≤0.15, for example, it can be 0.05, 0.075, 0.1, 0.125 or 0.15, but not limited to the listed values, other values not listed in the value range are also applicable.

[0035] Preferably, the precipitant solution of step (1) and step (2) comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide or ammonium hydroxide.

[0036] Preferably, the concentration of the precipitant solution of step (1) and step (2) is 40g / L-500g / L, for example, it can be 50g / L, 100g / L, 200g / L, 300g / L, 400g / L or 500g / L, but not limited to the listed values, other values not listed in the value range are also applicable.

[0037] Preferably, the concentration of the complexing agent solution of step (1) and step (2) is 3g / L-6g / L, for example, it can be 3g / L, 4g / L, 5g / L or 6g / L, but not limited to the listed values, other values not listed in the value range are also applicable.

[0038] Preferably, the second bottom solution of step (1) comprises seed crystals, water, a precipitant and a complexing agent.

[0039] Preferably, the pH value of the second bottom solution of step (1) is 10.5-11.5, for example, it can be 10.5, 11 or 11.5, and the concentration of the complexing agent in the second bottom solution is 4g / L-5g / L, for example, it can be 4g / L, 4.5g / L or 5g / L, but not limited to the listed values, other values not listed in the value range are also applicable.

[0040] Preferably, in the second bottom solution of step (1), the content of seed crystals is 1g / L-1.5g / L, for example, it can be 1g / L, 1.1g / L, 1.2g / L, 1.3g / L, 1.4g / L or 1.5g / L, but not limited to the listed values, other values not listed in the value range are also applicable.

[0041] Preferably, the washing of step (1) comprises water washing and alkali washing.

[0042] Preferably, the number of water washing is 3-6 times, for example, it can be 3 times, 4 times, 5 times or 6 times, and the number of alkali washing is 3-6 times, for example, it can be 3 times, 4 times, 5 times or 6 times.

[0043] Preferably, the temperature of the drying in step (1) is in the range of 80-130 °C, for example it can be 80 °C, 90 °C, 100 °C, 110 °C, 120 °C or 130 °C, but is not limited to the listed values, other values not listed within the range of values are also applicable.

[0044] Preferably, the concentration of the second mixed metal salt solution in step (2) is in the range of 80-150 g / L, for example it can be 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L, but is not limited to the listed values, other values not listed within the range of values are also applicable.

[0045] Preferably, the molar ratio of nickel ions, cobalt ions, manganese ions and doping metal ions in the second mixed metal salt solution in step (2) is a:b:(1-a-b-c):c, wherein 0.75≤a≤0.90, for example it can be 0.75, 0.8, 0.85 or 0.9, 0.05≤b≤0.15, for example it can be 0.05, 0.075, 0.1, 0.125 or 0.15, 0.01≤c≤0.05, for example it can be 0.01, 0.02, 0.03, 0.04 or 0.05, the doping metal ions include any one or a combination of at least two of Zr, Mg, W or Mo.

[0046] Preferably, the first mixed metal salt solution in step (1) and the second mixed metal salt solution in step (2) each independently comprises any one or a combination of at least two of sulfate, nitrate or chloride

[0047] Preferably, the pH of the second co-precipitation reaction in step (2) is in the range of 10.5-11.5, for example it can be 10.5, 11 or 11.5, but is not limited to the listed values, other values not listed within the range of values are also applicable.

[0048] Preferably, the concentration of the complexing agent in the system of the second co-precipitation reaction in step (2) is in the range of 4-5 g / L, for example it can be 4 g / L, 4.5 g / L or 5 g / L, but is not limited to the listed values, other values not listed within the range of values are also applicable.

[0049] Preferably, the particle size D50 of the product of the second co-precipitation reaction in step (2) is in the range of 7.5-8.5 μm, for example it can be 7.5 μm, 7.75 μm, 8.0 μm, 8.25 μm or 8.5 μm, but is not limited to the listed values, other values not listed within the range of values are also applicable.

[0050] In a second aspect, the present application provides a shell-doped high-nickel ternary precursor, which is prepared by the preparation method according to the first aspect.

[0051] Preferably, the diameter distance (D90-D10) / D50 of the shell-doped high-nickel ternary precursor is between 0.7 and 1, for example, can be 0.7, 0.8, 0.9 or 1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0052] The present application can prepare a product with high sphericity, uniform particle distribution, no micro-cracking, diameter distance (D90-D10) / D50 between 0.7 and 1, and controllable shell thickness by a specific preparation method, the whole reaction condition is mild, the operation is simple, and the product can be produced in an industrialized manner.

[0053] In a third aspect, the present application provides an application of the shell-doped high-nickel ternary precursor according to the second aspect, which includes a positive electrode material for preparing a battery.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] (1) The present application first prepares a seed crystal containing no doping elements, and then performs a second co-precipitation reaction guided by the seed crystal to prepare a doped shell on the surface of the seed crystal. Before the second co-precipitation reaction, the seed crystal is prepared into a second bottom solution, and the second bottom solution is subjected to seed activation treatment to increase the specific surface area and surface roughness of the seed crystal, thereby promoting the co-precipitation of the second co-precipitation reaction product on the surface of the seed crystal, improving the bonding strength of the inner core and the shell, and improving the consistency of the product composition.

[0056] (2) The present application takes the high-nickel ternary precursor as a core part, and adds a doping element in the shell structure to maintain the structural stability of the precursor and act as a protective barrier for the core material, which does not cause excessive capacity loss, and enables the precursor material to obtain the maximum possible capacity and protect the structural stability without using excessive doping materials; specifically, the doping element is substituted in the crystal lattice and segregated at the grain boundary to inhibit cation mixing, which can maintain the layered structure during the cycle process and prevent the formation of micro-cracks in the secondary particles, and also forms an effective thin protective layer on the surface, thereby minimizing the blockage of the (lithium ion) channel. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 The structural schematic diagram of the preparation method according to Example 1 of the present application. DETAILED DESCRIPTION

[0058] The technical solutions of the present application are further illustrated below by means of specific embodiments. Those skilled in the art should understand that the embodiments are only used for understanding the present application and should not be regarded as specific limitations on the present application.

[0059] Embodiment 1

[0060] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, a flow chart of the preparation method is shown as Figure 1 The preparation method comprises the following steps:

[0061] (1) A sulfate solution with a molar ratio of nickel ions, cobalt ions and manganese ions of 0.9:0.05:0.05 and a concentration of 150 g / L is configured as a first mixed metal salt solution, a sodium hydroxide solution with a concentration of 40 g / L is configured as a precipitant solution, ammonia water with a concentration of 5 g / L is configured as a complexing agent solution, and a sulfate solution with a molar ratio of nickel ions, cobalt ions, manganese ions and doped metal ions (specifically Zr) of 0.89:0.05:0.05:0.01 and a concentration of 150 g / L is configured as a second mixed metal salt solution;

[0062] (2) Pure water, sodium hydroxide and ammonia water are added to a reaction kettle as a first bottom liquid, nitrogen is introduced, the pH of the first bottom liquid is controlled to be 11, and the ammonia concentration is in the range of 4.5 g / L; the first mixed metal salt solution, the precipitant solution and the complexing agent solution are simultaneously added to the first bottom liquid by a peristaltic pump, the stirring speed of the reaction kettle is set to 700 rpm, the reaction temperature is controlled to be 58℃, the ammonia concentration is controlled to be in the range of 4-5 g / L, and the pH is controlled to be in the range of 11-11.5 to perform a nucleation reaction, when the product particle size D50 is 1.5 μm, the reaction pH is adjusted to be in the range of 10.5-11.0 to perform a crystal growth reaction, and a crystal seed slurry with a crystal seed particle size D50 of 4 is obtained;

[0063] (3) The crystal seed slurry is transferred to a suction filter bottle, washed with pure water for 4 times first, then washed with liquid alkali for 4 times, and dried at 100℃ to obtain the crystal seed;

[0064] (4) The crystal seed, pure water, sodium hydroxide and ammonia water are added to a reaction kettle as a second bottom liquid, the pH of the second bottom liquid is controlled to be 11, the ammonia concentration in the second bottom liquid is 4 g / L, the content of the crystal seed in the second bottom liquid is 1.2 g / L, the volume ratio of oxygen and nitrogen introduced is 1:300, the crystal seed is activated at a temperature of 60℃ and a stirring speed of 500 rpm for 1.5 h to obtain an activated bottom liquid;

[0065] (5) The second mixed metal salt solution, the precipitant solution and the complexing agent solution are simultaneously added into the activated base solution by using a peristaltic pump, nitrogen is simultaneously introduced, the stirring speed of the reaction kettle is set to 700 rpm, the reaction temperature is controlled to be 58℃, the ammonia concentration is controlled to be in the range of 4-5 g / L, and the pH is controlled to be in the range of 10.5-11.0, so as to carry out the second coprecipitation reaction, the reaction is stopped until the product particle size D50 is 3.5 μm, the reaction slurry is filtered, washed and dried at 100℃, and the shell-doped high-nickel ternary precursor is obtained.

[0066] Example 2

[0067] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which comprises the following steps:

[0068] (1) A sulfate solution with a molar ratio of nickel ions, cobalt ions and manganese ions of 0.85:0.075:0.075 and a concentration of 120 g / L is configured as a first mixed metal salt solution, a sodium hydroxide solution with a concentration of 50 g / L is configured as a precipitant solution, ammonia water with a concentration of 6 g / L is configured as a complexing agent solution, and a sulfate solution with a molar ratio of nickel ions, cobalt ions, manganese ions and doped metal ions (specifically Mg) of 0.82:0.075:0.075:0.03 and a concentration of 120 g / L is configured as a second mixed metal salt solution;

[0069] (2) Pure water, sodium hydroxide and ammonia water are added into a reaction kettle as a first base solution, nitrogen is introduced, the pH of the first base solution is controlled to be 11.5, and the ammonia concentration is controlled to be in the range of 5 g / L; the first mixed metal salt solution, the precipitant solution and the complexing agent solution are simultaneously added into the first base solution by using a peristaltic pump, the stirring speed of the reaction kettle is set to 1000 rpm, the reaction temperature is controlled to be 50℃, the ammonia concentration is controlled to be in the range of 4-5 g / L, and the pH is controlled to be in the range of 11.5-12, so as to carry out a nucleation reaction, when the product particle size D50 is 2.0 μm, the pH is adjusted to be in the range of 11.0-11.5 to carry out a crystal growth reaction, and a crystal seed slurry with a crystal seed particle size D50 of 3.5 μm is obtained;

[0070] (3) The crystal seed slurry is transferred into a filter bottle, washed with pure water for 6 times, then washed with liquid alkali for 6 times, and dried at 130℃ to obtain a crystal seed;

[0071] (4) The crystal seed, pure water, sodium hydroxide and ammonia water are added into a reaction kettle as a second base solution, the pH of the second base solution is controlled to be 11.5, the ammonia concentration in the second base solution is 5 g / L, the content of the crystal seed in the second base solution is 1.5 g / L, oxygen and nitrogen with a volume ratio of 1:300 are introduced, the crystal seed is activated at a temperature of 55℃ and a stirring speed of 700 rpm for 1 h, and an activated base solution is obtained;

[0072] (5) The second mixed metal salt solution, the precipitant solution and the complexing agent solution are simultaneously added into the activated base solution by a peristaltic pump, nitrogen is simultaneously introduced, the stirring speed of the reaction kettle is set to 1000 rpm, the reaction temperature is controlled to 50℃, the ammonia concentration is controlled to be within 5 g / L, and the pH is controlled to be within 11.0-11.5, and then the second coprecipitation reaction is performed, the reaction is stopped after the product particle size D50 is 7.5 μm, the reaction slurry is filtered, washed and dried at 100℃, and the shell-doped high-nickel ternary precursor is obtained.

[0073] Example 3

[0074] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which comprises the following steps:

[0075] (1) A sulfate solution with a molar ratio of nickel ions, cobalt ions and manganese ions of 0.9:0.05:0.05 and a concentration of 80 g / L is configured as a first mixed metal salt solution, a sodium hydroxide solution with a concentration of 100 g / L is configured as a precipitant solution, ammonia water with a concentration of 3 g / L is configured as a complexing agent solution, and a sulfate solution with a molar ratio of nickel ions, cobalt ions, manganese ions and doping metal ions (specifically Zr) of 0.89:0.05:0.05:0.01 and a concentration of 80 g / L is configured as a second mixed metal salt solution;

[0076] (2) Pure water, sodium hydroxide and ammonia water are added into a reaction kettle as a first base solution, nitrogen is introduced, the pH of the first base solution is controlled to be 10.5, and the ammonia concentration is controlled to be within 4 g / L; the first mixed metal salt solution, the precipitant solution and the complexing agent solution are simultaneously added into the first base solution by a peristaltic pump, the stirring speed of the reaction kettle is set to 500 rpm, the reaction temperature is controlled to be 60℃, the ammonia concentration is controlled to be within 4-5 g / L, the pH is controlled to be within 11-11.5, and then the nucleation reaction is performed, when the product particle size D50 is 1.0 μm, the pH is adjusted to be within 10.5-11.0 for the crystal growth reaction, and then the crystal seed slurry with a crystal seed particle size D50 of 4.5 μm is obtained;

[0077] (3) The crystal seed slurry is transferred into a filter bottle, washed with pure water for 3 times, then washed with liquid alkali for 3 times, and dried at 80℃ to obtain the crystal seed;

[0078] (4) The crystal seed, pure water, sodium hydroxide and ammonia water are added into a reaction kettle as a second base solution, the pH of the second base solution is controlled to be 11-11.5, the ammonia concentration in the second base solution is 4 g / L, the content of the crystal seed in the second base solution is 1.0 g / L, the volume ratio of oxygen and nitrogen introduced is 1.5:300, the crystal seed is activated at a temperature of 65℃ and a stirring speed of 600 rpm for 2 h, and then the activated base solution is obtained;

[0079] (5) The second mixed metal salt solution, the precipitant solution and the complexing agent solution are simultaneously added into the activated base solution by a peristaltic pump, nitrogen is simultaneously introduced, the stirring speed of the reaction kettle is set to 500 rpm, the reaction temperature is controlled to be 60°C, the ammonia concentration is controlled to be in the range of 4-5 g / L, and the pH is controlled to be in the range of 10.5-11.0, and then the second co-precipitation reaction is performed, and the reaction is stopped after the product particle size D50 is 8.5 μm, the reaction slurry is filtered, washed and dried at 100°C, and the shell-doped high-nickel ternary precursor is obtained.

[0080] Example 4

[0081] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which is the same as that of Example 1 except that the pH in step (2) and step (5) is in the range of 11-11.5.

[0082] Example 5

[0083] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which is the same as that of Example 1 except that the volume ratio of oxygen to nitrogen in step (4) is 3.5:300.

[0084] Example 6

[0085] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which is the same as that of Example 1 except that the seed activation treatment in step (4) is performed under a nitrogen atmosphere.

[0086] Example 7

[0087] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which is the same as that of Example 1 except that the seed activation treatment in step (4) is performed for 0.5 h.

[0088] Example 8

[0089] The present embodiment provides a preparation method of a shell-doped high-nickel ternary precursor, which is the same as that of Example 1 except that the seed activation treatment in step (4) is performed for 3 h.

[0090] Comparative Example 1

[0091] The present comparative example provides a preparation method of a high-nickel ternary precursor, which is the same as that of Example 1 except that the second mixed metal salt solution in step (5) is the same as the first mixed metal salt solution and does not contain doping ions.

[0092] Comparative Example 2

[0093] The comparative example provides a preparation method of a high-nickel ternary precursor, which is the same as the first mixed metal salt solution in step (2) and the second mixed metal salt solution in step (5) except that both contain doping ions, and the rest is the same as example 1.

[0094] The high-nickel ternary precursor obtained in the above examples and comparative examples is mixed with lithium hydroxide, and then sintered at a temperature of 700℃ for 10h to obtain a positive electrode material; the positive electrode material is prepared into a positive electrode sheet, and then a lithium sheet, a polypropylene separator and a lithium hexafluorophosphate electrolyte are prepared into a button cell, and the capacity and 1C discharge capacity / 1C charge capacity of the button cell are tested, wherein the voltage range for testing is 2.5V-4.3V.

[0095] The test results are shown in Table 1 below:

[0096] Table 1

[0097]

[0098] From the above Table 1, it can be seen that:

[0099] (1) From example 1 and comparative example 1, it can be seen that the present application significantly improves the stability and rate performance of the material under the premise of only a small decrease in the capacity of the material by doping in the shell layer, thereby ultimately optimizing the cycle performance of the battery; from example 1 and comparative example 2, it can be seen that the full-doping scheme of comparative example 2 is not preferred due to a significant decrease in capacity, while the shell-doping scheme of the present application can simultaneously take into account good capacity retention, structural stability and particle uniformity, thereby obtaining better comprehensive performance.

[0100] (2) Based on the comparison of example 1 and examples 4-6, it can be seen that the synthesis process of the present application has strict requirements for operating parameters, and any deviation of key conditions, including pH value exceeding the specified range (example 4), too high oxygen ratio (example 5) or complete absence of oxygen atmosphere (example 6), will cause specific material defects, respectively, abnormal morphology, excessive oxidation, and poor bonding and wide particle size distribution, which ultimately lead to a decrease in battery cycle performance. From example 1 and examples 7-8, it can be seen that the time of seed activation treatment will affect the seed activation effect, thereby affecting the structural stability of the material.

[0101] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a shell-doped high-nickel ternary precursor, characterized in that, The preparation method includes the following steps: (1) The first mixed metal salt solution, precipitant solution and complexing agent solution are passed into the first base liquid to carry out the first coprecipitation reaction to obtain a seed slurry. The seed slurry is subjected to solid-liquid separation, washing and drying to obtain a seed crystal. The seed crystal is prepared into a second base liquid. The second base liquid is subjected to seed crystal activation treatment to obtain an activated base liquid. (2) Pass the second mixed metal salt solution, precipitant solution and complexing agent solution into the activation base liquid in step (1) to carry out the second co-precipitation reaction and obtain the shell-doped high-nickel ternary precursor; The second mixed metal salt solution contains doped metal ions.

2. The preparation method according to claim 1, characterized in that, The seed activation treatment in step (1) is carried out under stirring conditions; Preferably, the seed activation treatment in step (1) is carried out in an oxygen-containing atmosphere; Preferably, the temperature of the seed activation treatment in step (1) is higher than the temperature of the first coprecipitation reaction in step (1) and the second coprecipitation reaction in step (2); Preferably, the oxygen content in the reaction atmosphere of the seed activation treatment in step (1) is greater than the oxygen content in the reaction atmosphere of the first coprecipitation reaction in step (1) and the second coprecipitation reaction in step (2).

3. The preparation method according to claim 1 or 2, characterized in that, The seed activation treatment in step (1) takes 1-2 hours; Preferably, the temperature for the seed activation treatment in step (1) is 55℃-65℃; Preferably, the stirring rate of the seed activation treatment in step (1) is 600 rpm-700 rpm; Preferably, the seed activation treatment in step (1) is carried out in oxygen and a protective gas; Preferably, the volume ratio of oxygen to protective gas is (1-1.5):

300.

4. The preparation method according to claim 1 or 2, characterized in that, In step (1), the temperatures of the first coprecipitation reaction and the second coprecipitation reaction are independently 50℃-65℃; Preferably, in step (1), the stirring rates of the first coprecipitation reaction and the second coprecipitation reaction are independently 500 rpm to 1000 rpm; Preferably, in the system of the first coprecipitation reaction in step (1), the concentration of the complexing agent is in the range of 4-5 g / L; Preferably, step (1) the first coprecipitation reaction includes a nucleation reaction and a growth reaction performed sequentially, wherein the pH of the nucleation reaction is in the range of 11-12 and the pH of the growth reaction is in the range of 10.5-11.5; Preferably, the particle size D50 of the particles obtained after the nucleation reaction is 1μm-2μm; Preferably, the seed crystals in step (1) have a particle size D50 of 3.5 μm-4.5 μm.

5. The preparation method according to claim 1 or 2, characterized in that, Step (1) The pH of the first base solution is 10.5-11.5, and the concentration of the complexing agent in the first base solution is in the range of 4g / L-5g / L; Preferably, in step (1), the concentration of the first mixed metal salt solution is 80 g / L-150 g / L; Preferably, in step (1), the molar ratio of nickel ions, cobalt ions and manganese ions in the first mixed metal salt solution is x:y:(1-xy), where 0.8≤x≤0.93 and 0.05≤y≤0.15; Preferably, the precipitant solution in steps (1) and (2) includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonium hydroxide; Preferably, the concentration of the precipitant solution in steps (1) and (2) is 40 g / L-500 g / L; Preferably, the concentration of the complexing agent solution in steps (1) and (2) is 3 g / L-6 g / L.

6. The preparation method according to claim 1 or 2, characterized in that, Step (1) The second base solution includes seed crystals, water, precipitant and complexing agent; Preferably, in step (1), the pH value of the second base solution is 10.5-11.5, and the concentration of the complexing agent in the second base solution is 4g / L-5g / L; Preferably, in step (1), the content of seed crystals in the second base solution is 1 g / L-1.5 g / L; Preferably, the washing in step (1) includes water washing and alkaline washing; Preferably, the number of water washes is 3 to 6 times, and the number of alkaline washes is 3 to 6 times; Preferably, the drying temperature in step (1) is 80℃-130℃.

7. The preparation method according to claim 1 or 2, characterized in that, In step (2), the concentration of the second mixed metal salt solution is 80 g / L-150 g / L; Preferably, in step (2), the molar ratio of nickel ions, cobalt ions, manganese ions and doped metal ions in the second mixed metal salt solution is a:b:(1-abc):c, where 0.75≤a≤0.90, 0.05≤b≤0.15, 0.01≤c≤0.05, and the doped metal ions include any one or at least two of Zr, Mg, W or Mo.

8. The preparation method according to claim 1 or 2, characterized in that, In step (2), the pH of the second coprecipitation reaction is in the range of 10.5-11.5; Preferably, in the system of the second coprecipitation reaction in step (2), the concentration of the complexing agent is in the range of 4 g / L-5 g / L; Preferably, in step (2), the second coprecipitation reaction continues until the product particle size D50 reaches 7.5 μm-8.5 μm.

9. A shell-doped high-nickel ternary precursor, characterized in that, The shell-doped high-nickel ternary precursor is prepared by the preparation method according to any one of claims 1-8.

10. An application of the shell-doped high-nickel ternary precursor as described in claim 9, characterized in that, The applications include the preparation of positive electrode materials for batteries.

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