Improved high-nickel precursor material as well as preparation method and application thereof

Abstract

The invention provides an improved high-nickel precursor material as well as a preparation method and application thereof. The preparation method comprises the following steps: introducing a mixed metal salt solution, a precipitant solution and a first complexing agent solution into a base solution to carry out a coprecipitation nucleation reaction; the first complexing agent solution comprises ammonium salt, the base solution comprises a second complexing agent, and the second complexing agent is different from a complexing agent in the first complexing agent solution in variety; and after the coprecipitation nucleation reaction is finished, continuously carrying out coprecipitation growth reaction in an oxygen-containing atmosphere to obtain the improved high-nickel precursor material. The preparation method disclosed by the invention is an improved low-ammonia coprecipitation method, the high-nickel precursor material with narrow particle size distribution and good sphericity degree can be obtained by adopting ammonium salt as a complexing agent and combining with adjustment of a reaction atmosphere, the treatment cost of production wastewater is reduced, and the damage of a high-ammonia production environment to a human body and the environment is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of battery materials and relates to an improved high-nickel precursor material and a preparation method and application thereof. Background Art

[0002] As the global demand for clean energy and sustainable transportation continues to grow, high-energy-density lithium-ion batteries have become a hot topic of research. Among the many lithium-ion battery cathode materials, high-nickel-content layered oxide cathode materials have attracted much attention due to their advantages such as high specific capacity, low cost and abundant resources. However, high-nickel cathode materials face many challenges in practical applications, such as poor structural stability, easy phase change, and electrolyte decomposition during charging and discharging, which seriously affect the cycle life and safety of the battery.

[0003] The traditional coprecipitation method is one of the commonly used technologies for synthesizing high-nickel precursors. This method usually relies on ammonia water as a complexing agent to control the precipitation process of metal ions. However, the concentration of ammonia used in this process is high, and there are many problems. First, ammonia is an inorganic gas that is slightly toxic, corrosive, and has a pungent odor, which poses a serious threat to human health. Long-term exposure to a high concentration of ammonia may cause irritation to the skin, eyes, and respiratory tract, and even lead to more serious health problems such as pulmonary edema or pulmonary hemorrhage. Secondly, the production process with high ammonia concentration will also produce a large amount of ammonia-containing wastewater. If these wastewaters are not properly treated, they will directly pollute the water body, destroy the ecological balance, and cause irreversible damage to the environment. In addition, the synthesis environment with high ammonia concentration may also affect the quality and performance of the material. In the coprecipitation process, the control of ammonia concentration is crucial to the formation of uniform and high-quality precursors. However, too high ammonia concentration often leads to too fast a reaction rate, which is difficult to accurately control, thereby affecting the particle size distribution, morphology and chemical composition of the material, and then affecting the electrochemical properties of the final material.

[0004] Based on the above research, there is a need to provide an improved method for preparing a high-nickel precursor material, which can obtain a high-nickel precursor with a narrow particle size distribution and good sphericity, and can reduce harm to the environment and human health. Summary of the invention

[0005] The purpose of the present invention is to provide an improved high-nickel precursor material and a preparation method and application thereof. The preparation method is an improved low-ammonia co-precipitation method. By using ammonium salt as a complexing agent combined with the adjustment of the reaction atmosphere, a high-nickel precursor material with a narrow particle size distribution and good sphericity can be obtained, and the treatment cost of production wastewater is reduced, avoiding damage to the human body and the environment caused by a high-ammonia production environment.

[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 an improved high-nickel precursor material, the preparation method comprising the following steps:

[0008] (1) introducing a mixed metal salt solution, a precipitant solution and a first complexing agent solution into a base solution to perform a coprecipitation nucleation reaction;

[0009] The first complexing agent solution includes an ammonium salt,

[0010] The base solution includes a second complexing agent, and the second complexing agent is of a different type from the complexing agent in the first complexing agent solution;

[0011] (2) After the coprecipitation nucleation reaction in step (1) is completed, the coprecipitation growth reaction is continued in an oxygen-containing atmosphere to obtain the improved high-nickel precursor material.

[0012] The invention adopts ammonium salt instead of ammonia water as the complexing agent of the coprecipitation reaction, utilizes the ammonia water generated by the reaction of the precipitant and the ammonium salt to carry out complexation and precipitation, thereby slowing down the growth rate of the precursor, and the invention combines the control of the reaction atmosphere so that the coprecipitation growth reaction is carried out in an oxygen-containing atmosphere, thereby further slowing down the growth rate of the precursor, thereby not only optimizing the particle size distribution, particle morphology and element composition of the precursor, but also reducing the treatment cost of production wastewater, thereby avoiding the damage of the ammonia water production environment to the human body and the environment; in addition, the invention further contains a non-ammonium salt complexing agent in the reaction base liquid, thereby being able to provide an environment with a uniform and stable complexing agent concentration in the nucleation stage.

[0013] Preferably, in step (1), the second complexing agent comprises aqueous ammonia.

[0014] The complexing agent added to the base liquid of the present invention is ammonia water, rather than ammonium salt, in order to provide an environment with uniform and stable ammonia concentration during the nucleation stage. Otherwise, there will be too little free ammonia during the nucleation stage, the particle size will be out of control, and small irregular particles will be generated.

[0015] Preferably, the ammonium salt in step (1) comprises any one of ammonium nitrate, ammonium sulfate or ammonium chloride, or a combination of at least two thereof, preferably ammonium sulfate.

[0016] Preferably, in the first complexing agent solution in step (1), the ammonium ion concentration is 0.1-1.0 mol / L, for example, it can be 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L or 1.0 mol / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.2-0.5 mol / L.

[0017] Preferably, the base liquid in step (1) further comprises water and a precipitant.

[0018] Preferably, the pH of the base solution in step (1) is 11.5-12.8, for example, it can be 11.5, 11.7, 11.9, 12.1, 12.3, 12.5 or 12.8, and the ammonia concentration is 0.5-4 g / L, for example, it can be 0.5 g / L, 1.5 g / L, 2.5 g / L, 3.5 g / L or 4 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the pH of the coprecipitation nucleation reaction in step (1) is 11.4-12.6, for example, it can be 11.4, 11.6, 11.8, 12.0, 12.2, 12.4 or 12.6, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 11.7-12.1.

[0020] Preferably, the time of the coprecipitation nucleation reaction in step (1) is 2-10 h, for example, 2 h, 4 h, 6 h, 8 h or 10 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable, preferably 4-6 h.

[0021] Preferably, the temperature of the coprecipitation nucleation reaction in step (1) is 40-70°C, for example, 40°C, 50°C, 60°C or 70°C, and the rotation speed is 200-500rpm, for example, 200rpm, 300rpm, 400rpm or 500rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the coprecipitation nucleation reaction in step (1) is carried out in a protective atmosphere, and the protective atmosphere comprises nitrogen and / or argon.

[0023] Preferably, the total metal ion concentration of the mixed metal salt solution in step (1) is 1.0-3.0 mol / L, for example, 1.0 mol / L, 2.0 mol / L or 3.0 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the mixed metal salt solution in step (1) comprises any one of sulfate, nitrate or halide or a combination of at least two thereof, preferably sulfate.

[0025] Preferably, the mass percentage of the precipitant solution in step (1) is 20-40wt%, for example, 20wt%, 30wt% or 40wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the precipitant solution in step (1) comprises any one of sodium hydroxide, potassium hydroxide or lithium hydroxide, or a combination of at least two thereof.

[0027] Preferably, the ammonia concentration during the coprecipitation growth reaction in step (2) is 0.5-3 g / L, for example, it can be 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L or 3 g / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1.0-2 g / L.

[0028] The coprecipitation growth reaction of the present invention is carried out at a lower ammonia concentration, which slows down the growth rate of the precursor and allows the precursor particles to be grown at a lower ammonia concentration, thereby controlling the growth of the precursor particles and obtaining a precursor material with a narrow particle size distribution and good sphericity.

[0029] Preferably, the pH of the coprecipitation growth reaction in step (2) is 9.5-10.8, for example, it can be 9.5, 9.7, 9.9, 10.1, 10.3, 10.5 or 10.8, but is not limited to the listed values. Other values ​​not listed in the numerical range are also applicable, preferably 9.8-10.4.

[0030] Preferably, the temperature of the coprecipitation growth reaction in step (2) is 40-70°C, for example, 40°C, 50°C, 60°C or 70°C, and the rotation speed is 200-500rpm, for example, 200rpm, 300rpm, 400rpm or 500rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, in the oxygen-containing atmosphere of step (2), the volume fraction of oxygen is 1-10%, for example, 1%, 3%, 5%, 7%, 9% or 10%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 3-6%.

[0032] Preferably, the oxygen-containing atmosphere in step (2) includes a mixture of nitrogen and air, a mixture of nitrogen and oxygen, a mixture of argon and air, or a mixture of argon and oxygen.

[0033] Preferably, after the coprecipitation nucleation reaction in step (2) is completed, the flow rates of the precipitant solution and the first complexing agent solution are gradually reduced.

[0034] Preferably, the particle size D50 of the particles grown by the coprecipitation reaction in step (2) is 5-20 μm, for example, 5 μm, 10 μm, 15 μm or 20 μm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 8-14 μm.

[0035] Preferably, after the coprecipitation growth reaction in step (2), washing and drying are also performed.

[0036] Preferably, the washing comprises alkali washing and water washing.

[0037] Preferably, the washing is performed by alkali washing first and then water washing, and the number of alkali washing and water washing is more than two times, for example, it can be two, three or four times, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0038] Preferably, the drying temperature is 80-150°C, for example, 80°C, 100°C, 120°C, 140°C or 150°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the water content of the improved high-nickel precursor material in step (2) is below 1.0wt%, for example, it can be 1.0wt%, 0.75wt%, 0.5wt% or 0.25wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In a second aspect, the present invention provides an improved high-nickel precursor material, which is prepared by the preparation method described in the first aspect.

[0041] Preferably, the chemical formula of the improved high nickel precursor material is Ni x Co y Mn 1-x-y (OH)2、Ni x Co y Al 1-x-y (OH)2 or Ni x Mn 1-x (OH)2, wherein 0.7≤x<1, for example, it can be 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, and 0≤y≤0.3, for example, it can be 0, 0.05, 0.1, 0.15, 0.2, 0.25 or 0.3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] In a third aspect, the present invention provides a lithium-ion battery, comprising a positive electrode material, wherein the positive electrode material is obtained by mixing and sintering a lithium source and the improved high-nickel precursor material as described in the second aspect.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention adopts ammonium salt instead of ammonia water as the complexing agent of the coprecipitation reaction, utilizes ammonia water generated by the reaction of the precipitant and the ammonium salt for complexation and precipitation, and slows down the growth rate of the precursor. In addition, the present invention combines the control of the reaction atmosphere so that the coprecipitation growth reaction is carried out in an oxygen-containing atmosphere, and further slows down the growth rate of the precursor. Not only the particle size distribution, particle morphology and element composition of the precursor are optimized, but also the treatment cost of production wastewater is reduced, and the damage to human body and environment caused by the ammonia water production environment is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a SEM image of the improved high-nickel precursor material obtained in Example 1 of the present invention;

[0046] Figure 2 This is a SEM image of the high-nickel precursor material obtained in Comparative Example 1 of the present invention;

[0047] Figure 3 This is a SEM image of the high-nickel precursor material obtained in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0049] Example 1

[0050] This embodiment provides a method for preparing an improved high-nickel precursor material, the preparation method comprising the following steps:

[0051] (1) According to the molecular formula Ni 0.96 Co 0.02 Mn 0.02 (OH)2 (NCM960202) was used to prepare a mixed metal sulfate solution with a total metal ion concentration of 2 mol / L; an ammonium sulfate solution with an ammonium ion concentration of 0.3 mol / L was prepared; a sodium hydroxide solution with a mass fraction of 30 wt% was prepared; a reaction base solution with a pH of 12.0±0.2 and an ammonia concentration of 2.0±0.3 g / L was prepared using the sodium hydroxide solution, concentrated ammonia water and 20 L of pure water;

[0052] (2) Under the protection of nitrogen atmosphere, the prepared mixed metal sulfate solution, sodium hydroxide solution and ammonium sulfate solution were added to a 50L reactor containing the reaction base liquid at flow rates of 2.4 kg / h, 1.2 kg / h and 0.2 kg / h, respectively, in a uniform and parallel flow manner to carry out the nucleation stage reaction of coprecipitation. The pH value of the nucleation stage was controlled at 11.9±0.2 and maintained for 5 hours, and the ammonia concentration was maintained in the range of 2.0±0.3 g / L;

[0053] (3) After the nucleation is completed, the nitrogen gas is switched to a mixture of nitrogen gas and air with an oxygen volume fraction of about 5%, and the feed flow rates of the sodium hydroxide solution and the ammonium sulfate solution are gradually reduced, so that the pH of the reaction system reaches the target pH of the growth stage within 8 hours = 10.2 ± 0.1, and the ammonia concentration is 1.5 ± 0.3 g / L. When the median particle size D50 of the particles reaches 10 μm, the feed is stopped to obtain a precursor slurry; wherein, the reaction temperature of the entire coprecipitation reaction is maintained at 60 ± 1 ° C, and the stirring speed is 300 rpm;

[0054] The precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then dried at 100° C. for 12 hours to obtain the improved high-nickel precursor material. The SEM image of the improved high-nickel precursor material is as follows: Figure 1 shown.

[0055] Example 2

[0056] This embodiment provides a method for preparing an improved high-nickel precursor material, the preparation method comprising the following steps:

[0057] (1) According to the molecular formula Ni 0.90 Co 0.05 Mn 0.05 (OH)2 was used to prepare a mixed metal sulfate solution with a total metal ion concentration of 1.0 mol / L; an ammonium sulfate solution with an ammonium ion concentration of 1.0 mol / L was prepared; a sodium hydroxide solution with a mass fraction of 40 wt% was prepared; a reaction base solution with a pH of 12.8 ± 0.2 and an ammonia concentration of 4 ± 0.5 g / L was prepared using the sodium hydroxide solution, concentrated ammonia water and 20 L of pure water;

[0058] (2) Under the protection of nitrogen atmosphere, the prepared mixed metal sulfate solution, sodium hydroxide solution and ammonium sulfate solution were added to a 50L reactor containing the reaction base liquid at flow rates of 2.4 kg / h, 1.2 kg / h and 0.2 kg / h, respectively, in a uniform and parallel flow manner to carry out the nucleation stage reaction of coprecipitation. The nucleation stage was controlled at a pH of 12.8±0.2 and maintained for 2 hours, and the ammonia concentration was maintained in the range of 4±0.5 g / L;

[0059] (3) After the nucleation is completed, the nitrogen gas is switched to a mixture of nitrogen gas and air with a volume fraction of 6% oxygen, and the feed flow rate of the sodium hydroxide solution and the ammonium sulfate solution is gradually reduced, so that the pH of the reaction system reaches the target pH of 10.8±0.1 in the growth stage within 6 hours, and the ammonia concentration is 3±0.5 g / L. When the median particle size D50 of the particles reaches 20 μm, the feed is stopped to obtain a precursor slurry; wherein, the reaction temperature of the entire coprecipitation reaction is maintained at 40° C., and the stirring speed is 200 rpm;

[0060] The precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then baked at 150° C. for 12 hours to obtain the improved high-nickel precursor material.

[0061] Example 3

[0062] This embodiment provides a method for preparing an improved high-nickel precursor material, the preparation method comprising the following steps:

[0063] (1) According to the molecular formula Ni 0.96 Co 0.02 Mn 0.02 (OH)2 (NCM960202) was used to prepare a mixed metal sulfate solution with a total metal ion concentration of 3.0 mol / L; an ammonium nitrate solution with an ammonium radical concentration of 0.1 mol / L was prepared; a sodium hydroxide solution with a mass fraction of 20 wt% was prepared; a reaction base solution with a pH of 11.5±0.2 and an ammonia concentration of 0.5±0.2 g / L was prepared using the sodium hydroxide solution, concentrated ammonia water and 20 L of pure water;

[0064] (2) under the protection of nitrogen atmosphere, the prepared mixed metal sulfate solution, sodium hydroxide solution and ammonium nitrate solution were added to a 50L reactor containing the reaction base liquid at flow rates of 2.4kg / h, 1.2kg / h and 0.2kg / h, respectively, in a uniform and parallel flow manner to carry out the nucleation stage reaction of coprecipitation. The nucleation stage was controlled at a pH of 11.5±0.2 and maintained for 10 hours, and the ammonia concentration was maintained in the range of 1.0±0.2g / L;

[0065] (3) After the nucleation is completed, the nitrogen gas is switched to a mixture of nitrogen gas and air with a volume fraction of 10% oxygen, and the feed flow rate of the sodium hydroxide solution and the ammonium sulfate solution is gradually reduced, so that the pH of the reaction system reaches the target pH of 9.5±0.2 in the growth stage within 10 hours, and the ammonia concentration is 0.5±0.2 g / L. When the median particle size D50 of the particles reaches 5 μm, the feed is stopped to obtain a precursor slurry; wherein, the reaction temperature of the entire coprecipitation reaction is maintained at 70° C., and the stirring speed is 500 rpm;

[0066] The precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then dried at 80° C. for 12 hours to obtain the improved high-nickel precursor material.

[0067] Example 4

[0068] This embodiment provides an improved method for preparing a high-nickel precursor material. The preparation method is the same as that of Embodiment 1 except that the feed flow rate of the ammonium sulfate solution is changed so that the ammonia concentration in the growth stage of step (3) is 0.2 g / L.

[0069] Example 5

[0070] This embodiment provides an improved method for preparing a high-nickel precursor material. The preparation method is the same as that of Embodiment 1 except that the feed flow rate of the ammonium sulfate solution is changed so that the ammonia concentration in the growth stage of step (3) is 4 g / L.

[0071] Example 6

[0072] This embodiment provides an improved method for preparing a high-nickel precursor material. The preparation method is the same as that of Embodiment 1 except that the volume fraction of oxygen in the mixed gas in step (3) is 1%.

[0073] Example 7

[0074] This embodiment provides an improved method for preparing a high-nickel precursor material. The preparation method is the same as that of Embodiment 1 except that the volume fraction of oxygen in the mixed gas in step (3) is 0.5%.

[0075] Example 8

[0076] This embodiment provides an improved method for preparing a high-nickel precursor material. The preparation method is the same as that of Embodiment 1 except that the volume fraction of oxygen in the mixed gas in step (3) is 15%.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a high-nickel precursor material, which is the same as Example 1 except that the ammonium sulfate solution of equal concentration in step (2) is replaced by ammonia water;

[0079] The SEM image of the high nickel precursor material in this comparative example is as follows Figure 2 shown.

[0080] Comparative Example 2

[0081] This comparative example provides a method for preparing a high-nickel precursor material, which is the same as Example 1 except that in step (1), the reaction base liquid is not added with concentrated ammonia water, but with an ammonium sulfate solution containing an equimolar amount of ammonium radicals.

[0082] The SEM image of the high nickel precursor material in this comparative example is as follows Figure 3 shown.

[0083] Comparative Example 3

[0084] This comparative example provides a method for preparing a high-nickel precursor material, which is the same as Example 1 except that step (3) is still carried out in a nitrogen atmosphere.

[0085] The TD and BET of the high-nickel precursor materials obtained in the above examples and comparative examples are shown in Table 1; the high-nickel precursor materials obtained in the above examples and comparative examples are uniformly mixed with lithium hydroxide according to a lithium ratio of Li / TM=1.03, sintered at 720°C for 18 hours to obtain a high-nickel positive electrode material, and assembled into button cells for electrochemical performance testing. The specific experimental steps are as follows: first, the active material (the high-nickel positive electrode material obtained by sintering), the conductive agent acetylene black, and the binder polyvinylidene fluoride are dissolved in N-methylpyrrolidone in a mass ratio of 8:1:1, and the slurry is mixed using a homogenizer in a multi-stage mode at room temperature; then, the ground slurry is evenly applied to the aluminum foil with a coater, and dried at 80°C in a vacuum drying oven for 12 hours; finally, the aluminum foil is punched into 1.13 cm 2 Circular electrode sheet.

[0086] The obtained electrode sheet was used as the positive electrode, the lithium metal sheet was used as the counter electrode, and the porous polypropylene membrane (Celgard2400, USA) was used as the separator to separate the positive electrode and the counter electrode. The CR-2032 battery was assembled in a glove box filled with Ar gas. The battery was tested using a battery test system (Blue Electric CT2001A, Wuhan, China). First, it was activated three times at 0.1C rate / 2.7~4.3V, and then the activated button cell was tested for electrochemical performance under the conditions of 2.7-4.3V@0.1C / 1C. The test results are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] From Table 1 we can see that:

[0091] (1) It can be seen from Example 1 and Comparative Example 1 that the complexing agent of the present invention uses ammonium salt and ammonia water is added to the base liquid, which can control the ammonia concentration of the coprecipitation reaction. In Comparative Example 1, ammonia water is used as the complexing agent, the ammonia concentration fluctuates greatly, the growth rate is fast, the TD is small, the particle size distribution range of the particles is slightly larger, small particles are generated, and cracks exist on the surface of some particles, which makes the capacity, rate performance and cycle performance of the battery obtained in Comparative Example 1 decrease. The 0.1C first discharge specific capacity decreases from 224.5mAh / g in Example 1 to 214.6mAh / g, the 1C / 0.1C capacity ratio decreases from 93.2% in Example 1 to 87.6%, and the 1C cycle 100-week capacity retention rate decreases from 0.1% in Example 1 to 0.1% in Example 1. 91.8% decreased to 85.3%; it can be seen from Example 1 and Comparative Example 2 that in Comparative Example 2, ammonium salt is added to the base liquid instead of ammonia water, so that there is too little free ammonia in the nucleation period, the particle size is out of control, small irregular particles are generated, and the precursor particles have obvious cracks, which seriously affect the performance of the battery, and the capacity, rate performance and cycle performance of the battery obtained in Comparative Example 2 are greatly reduced, the 0.1C first discharge specific capacity decreases from 224.5mAh / g in Example 1 to 209.7mAh / g, the 1C / 0.1C capacity ratio decreases from 93.2% in Example 1 to 84.8%, and the 1C cycle 100-week capacity retention rate decreases from 91.8% in Example 1 to 83.3%.

[0092] (2) At the same time, according to Figure 1-Figure 3 It can be seen that the present invention adopts an improved low-ammonia coprecipitation method, combined with the use of ammonium salt and a micro-oxidizing atmosphere to slow down the growth rate of the precursor, and achieve a narrow distribution of the precursor particle size and optimization of the particle morphology; from Example 1 and Comparative Example 3, it can be seen that the micro-oxidizing atmosphere and the use of ammonium salt in the present invention can cooperate with each other to slow down the growth of the precursor, thereby optimizing the particle size, morphology and performance of the precursor. If the growth stage is carried out in a nitrogen atmosphere, the capacity, rate performance and cycle performance of the battery will decrease. The 0.1C first discharge specific capacity of the battery obtained in Comparative Example 3 is 224.5 mAh / g lower than that of Example 1. It dropped to 215.2mAh / g, the 1C / 0.1C capacity ratio dropped from 93.2% in Example 1 to 88.5%, and the 1C cycle 100-week capacity retention rate dropped from 91.8% in Example 1 to 84.6%; It can be seen from Example 1 and Examples 4-5 that the ammonia concentration in the growth stage of the present invention will affect the growth of the particles, thereby affecting the particle size distribution of the precursor material, affecting the capacity, rate performance and cycle performance of the battery; It can be seen from Examples 1 and Examples 6-8 that the oxygen content in the growth stage of the present invention will also affect the growth rate of the particles, thereby affecting the particle size and morphology of the precursor and the performance of the battery.

[0093] In summary, the present invention provides an improved high-nickel precursor material, a preparation method and application thereof. The preparation method is an improved low-ammonia co-precipitation method. By using ammonium salt as a chelating agent combined with the adjustment of the reaction atmosphere, a high-nickel precursor material with a narrow particle size distribution and good sphericity can be obtained, and the treatment cost of production wastewater is reduced, avoiding damage to the human body and the environment caused by a high-ammonia production environment.

[0094] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an improved high-nickel precursor material, characterized in that: The preparation method comprises the following steps: (1) introducing a mixed metal salt solution, a precipitant solution and a first complexing agent solution into a base solution to perform a coprecipitation nucleation reaction; The first complexing agent solution includes an ammonium salt, The base solution includes a second complexing agent, and the second complexing agent is of a different type from the complexing agent in the first complexing agent solution; (2) After the coprecipitation nucleation reaction in step (1) is completed, the coprecipitation growth reaction is continued in an oxygen-containing atmosphere to obtain the improved high-nickel precursor material.

2. The preparation method according to claim 1, characterized in that: Step (1) the second complexing agent comprises aqueous ammonia; Preferably, the ammonium salt in step (1) comprises any one of ammonium nitrate, ammonium sulfate or ammonium chloride or a combination of at least two thereof, preferably ammonium sulfate; Preferably, in the first complexing agent solution in step (1), the ammonium ion concentration is 0.1-1.0 mol / L, preferably 0.2-0.5 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: The base liquid in step (1) further comprises water and a precipitant; Preferably, the pH of the base solution in step (1) is 11.5-12.8, and the ammonia concentration is 0.5-4 g / L; Preferably, the pH of the coprecipitation nucleation reaction in step (1) is 11.4-12.6, preferably 11.7-12.1; Preferably, the coprecipitation nucleation reaction time in step (1) is 2-10 h, preferably 4-6 h.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature of the coprecipitation nucleation reaction in step (1) is 40-70° C. and the rotation speed is 200-500 rpm; Preferably, the coprecipitation nucleation reaction in step (1) is carried out in a protective atmosphere; Preferably, the mixed metal salt solution in step (1) comprises any one or a combination of at least two of sulfate, nitrate or halide, preferably sulfate; Preferably, the total metal ion concentration of the mixed metal salt solution in step (1) is 1.0-3.0 mol / L; Preferably, the mass percentage of the precipitant solution in step (1) is 20-40wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The ammonia concentration during the coprecipitation growth reaction in step (2) is 0.5-3.0 g / L, preferably 1.0-2.0 g / L; Preferably, the pH during the coprecipitation growth reaction in step (2) is 9.5-10.8, preferably 9.8-10.4; Preferably, the temperature of the coprecipitation growth reaction in step (2) is 40-70° C. and the rotation speed is 200-500 rpm.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In the oxygen-containing atmosphere of step (2), the volume fraction of oxygen is 1-10%, preferably 3-6%; Preferably, the oxygen-containing atmosphere in step (2) includes a mixture of nitrogen and air, a mixture of nitrogen and oxygen, a mixture of argon and air, or a mixture of argon and oxygen; Preferably, after the coprecipitation nucleation reaction in step (2) is completed, the flow rates of the precipitant solution and the first complexing agent solution are gradually reduced.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Step (2) the coprecipitation growth reaction is carried out until the particle size D50 of the particles is 5-20 μm, preferably 8-14 μm; Preferably, after the coprecipitation growth reaction in step (2), washing and drying are also performed; Preferably, the washing comprises alkali washing and water washing.

8. An improved high nickel precursor material, characterized in that: The improved high-nickel precursor material is prepared by the preparation method described in any one of claims 1 to 7.

9. The improved high nickel precursor material according to claim 8, characterized in that: The chemical formula of the improved high nickel precursor material is Ni x Co y Mn 1-x-y (OH)2、Ni x Co y Al 1-x-y (OH)2 or Ni x Mn 1-x (OH)2, where 0.7≤x<1, 0≤y≤0.

3.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode material, which is obtained by mixing and sintering a lithium source and the improved high-nickel precursor material as claimed in claim 8 or 9.

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