Preparation method for high-nickel ternary precursor and use thereof

Abstract

Disclosed are a preparation method for a high-nickel ternary precursor and the use thereof. The preparation method comprises: under certain conditions, simultaneously introducing an alkali liquor and a metal salt solution for a precipitation reaction to obtain particles with D50 being 7.0-15.0 ?m, then introducing seed crystals, adjusting the D10 of the particles to be 2.0-7.0 ?m, then stopping introducing the seed crystals, continuously introducing the alkali liquor and the metal salt solution, collecting the overflow material, and when the particle size of the particles grows to D50 being 7.0-15.0 ?m, repeating the operation of adding the seed crystals, continuously collecting the overflow material, and finally, washing, drying and screening the collected material so as to obtain a high-nickel ternary precursor. In the present invention, the seed crystals are used to adjust the particle size, such that the particle size is kept in a proper wide distribution, the bulk density of the precursor is improved; and an intermittent-continuous production process by intermittent seed crystal addition and continuous discharging is used, such that the height constancy of a particle growth environment in the production process is ensured, and defects caused by the environmental fluctuation in the crystal grains are reduced.

Description

Preparation method and application of high nickel ternary precursor Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery positive electrode materials, and in particular relates to a preparation method of a high-nickel ternary precursor and application thereof. Background Art

[0002] In recent years, with the popularity of new energy electric vehicles, people's expectations for electric vehicle range have become increasingly higher. The key to improving range lies in increasing the energy density of the power batteries installed in vehicles. In the absence of significant breakthroughs in battery systems, increasing the capacity of batteries per unit volume is currently the focus of research and development. Based on this, the requirements for the compaction density of battery positive electrode active materials are also becoming increasingly stringent. The compaction density of positive electrode materials is directly related to the compaction density of the precursor. This requires the precursor to have a high compaction density and, at the same time, high structural strength of the particles under high pressure to prevent them from being crushed and decomposed during rolling and cycling compared to traditional materials. Research has shown that this material particle fracture caused by physical and chemical reactions is also related to the physical strength of the precursor. Improving the physical resistance of the precursor to fracture can also help to improve the cracking problem of this type of material.

[0003] Previously, the industry did not pay much attention to the compaction density of precursors, nor did it use it as a quality indicator for product supply. Currently, in order to meet the goal of high capacity, while adopting high-nickel ternary materials, higher requirements are also put forward for the compaction density and crack resistance of high-nickel precursors. Products produced by traditional methods can no longer meet these requirements of high-nickel precursors.

[0004] A single ternary precursor particle can be considered a secondary spherical polycrystalline particle formed by stacking multiple primary grains. Direct contact surfaces between primary grains form grain boundaries, while non-contact surfaces form pores. When increasing pressure is applied to the precursor particle, stress increases, concentrating at lattice defects within the grain. When the stress limit is reached, dislocations form. Continued pressure causes dislocations to slip within the grain, propagating and growing to form slip bands. Grain boundaries are one of the greatest obstacles to dislocation movement. A slip band in one grain cannot propagate across a grain boundary to an adjacent grain. To propagate to an adjacent grain, it must initiate dislocation sources in adjacent grains to generate new slip bands. The propagation of slip bands between grains ultimately causes the polycrystalline particle to fracture and decompose. This indicates that increasing the number of grain boundaries is an important means of improving a material's resistance to cracking. Furthermore, appropriate pores within the material particle provide a buffer for elastic deformation under pressure. However, when pressure continues to increase, exceeding the yield limit, the material undergoes plastic deformation, leading to dislocations and causing the particle to fracture. It can be seen that appropriate porosity can provide a certain buffering effect when the particles are under pressure, but the more pores, the better. On the one hand, as the pores increase, the weight of the particles decreases, which will directly reduce the compaction density of the material. On the other hand, the internal volume of the particles is limited. When the pores increase, the number of grain boundaries will decrease accordingly, which will make the particles easier to crack.

[0005] For multiple secondary polycrystalline particles, the more concentrated the particle size distribution is, the better. This is because it is difficult for uniform particles to form dense stacking, and the particles will have larger pores. On the one hand, this will increase the macroscopic volume of the powder, which is not conducive to improving the compaction density. On the other hand, when the powder is subjected to pressure, there are fewer contact points between the particles, which easily leads to stress concentration, which is not conducive to improving the compressive resistance of the particles.

[0006] Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a preparation method and application of a high-nickel ternary precursor, which can meet the compaction density requirements of the high-nickel precursor and increase the crack resistance of the precursor particles.

[0008] According to one aspect of the present invention, a method for preparing a high-nickel ternary precursor is proposed, comprising the following steps:

[0009] S1: preparing a metal salt solution of nickel salt, cobalt salt and manganese salt;

[0010] S2: Under an inert atmosphere, heating and introducing ammonia water, then introducing alkali solution to adjust the pH, and then introducing alkali solution and the metal salt solution simultaneously to carry out a precipitation reaction to obtain particles with a D50 of 7.0 to 15.0 μm;

[0011] S3: When the D10 of the particles is adjusted to 2.0-7.0 μm by introducing seed crystals, the seed crystal introduction is stopped, the alkali solution and the metal salt solution are continuously introduced, and the overflowed material is collected. When the particle size grows to a D50 of 7.0-15.0 μm, the seed crystal addition operation is repeated, and the overflowed material is continuously collected;

[0012] S4: washing, drying and sieving the collected materials to obtain the high-nickel ternary precursor.

[0013] In some preferred embodiments of the present invention, in step S2, the particle size D50 of the particles is obtained to be 8.0-12.0 μm; in step S3, seed crystals are introduced to adjust the D10 of the particles to 2.0-5.0 μm; in step S3, when the particle size grows to D50 of 8.0-12.0 μm, the above-mentioned seeding operation is repeated.

[0014] In some embodiments of the present invention, the process for preparing the seed crystals is further included: adding water to the seed crystal reactor, introducing an inert gas, starting stirring and heating, introducing ammonia water, then introducing alkali solution to adjust the pH, and then introducing alkali solution and the metal salt solution at the same time to carry out a precipitation reaction, continuously feeding, filtering out the clear liquid from the seed crystal reactor to maintain a constant liquid level, continuously concentrating the material, and continuously growing the particles until the particle size grows to 2 to 7 μm, and then stopping the feeding to obtain the seed crystals; more preferably, stopping the feeding until the particle size grows to 2 to 5 μm.

[0015] In some embodiments of the present invention, during the preparation of seed crystals, the stirring speed is 150-300 rpm, the heating temperature is 50-80° C., the concentration of ammonia water in the seed crystal reactor is 0-10 g / L, and the pH is adjusted to 11.0-13.0.

[0016] In some embodiments of the present invention, in step S2, after adjusting the pH, seed crystals are first added, and then alkali solution and metal salt solution are simultaneously introduced to perform precipitation reaction, wherein the particle size of the seed crystals is 2 to 7 μm. The precursor is grown by seed crystal growth.

[0017] In some embodiments of the present invention, in step S1, the general structural formula of the high nickel ternary precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.6<x<1, 0<y<0.4, x+y<1.

[0018] In some embodiments of the present invention, in step S4, the particle size D10 of the high-nickel ternary precursor is 2.0-7.0 μm, D50 is 7.0-15.0 μm, and D90 is 12.0-20.0 μm.

[0019] In some preferred embodiments of the present invention, the particle size D10 of the high-nickel ternary precursor is 2.0-5.0 μm, D50 is 8.0-12.0 μm, and D90 is 18.0-20.0 μm.

[0020] In some embodiments of the present invention, in step S2, the precipitation reaction is continuously stirred throughout the entire process, and the stirring speed is 150-250 rpm.

[0021] In some embodiments of the present invention, in step S2, the stirring speed is 150-250 rpm.

[0022] In some embodiments of the present invention, in step S2, the heating temperature is 50-80°C.

[0023] In some embodiments of the present invention, in step S2, the concentration of the ammonia water is 0-10 g / L.

[0024] In some embodiments of the present invention, in step S2, the pH is adjusted to 11.0-13.0.

[0025] The present invention also proposes the application of the preparation method in the preparation of lithium ion batteries.

[0026] According to a preferred embodiment of the present invention, there are at least the following beneficial effects:

[0027] 1. The present invention adopts seed crystals to adjust the particle size, so that the particle size maintains an appropriate wide distribution, improves the bulk density of the precursor, and enhances the anti-cracking performance. The uniform particle size seed crystals also avoid the fine powder generated by particle size adjustment in the traditional continuous production process.

[0028] 2. The present invention adopts an intermittent-continuous production process with intermittent seed addition and continuous material discharge, which ensures a highly constant particle growth environment during the production process and reduces defects inside the grains caused by environmental fluctuations.

[0029] 3. The present invention adopts a pH range higher than the conventional one to refine the primary grains of the precursor, thereby increasing the number of grain boundaries and improving the crack resistance of the precursor particles.

[0030] 4. The present invention uses high-speed stirring to produce a smaller amount of pores inside the particles, thereby increasing the density of the particles. At the same time, high-speed stirring improves the sphericity of the particles. Higher sphericity is also beneficial for increasing the contact area between the particles when under pressure, thereby reducing stress concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0032] FIG1 is a process flow chart of the present invention;

[0033] FIG2 is a compaction density curve diagram of the precursors of Examples 1 and 2 and Comparative Examples 1 and 2;

[0034] FIG3 is a SEM image of the precursor of Example 1;

[0035] FIG4 is a cross-sectional SEM image of the precursor of Example 1. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0037] Example 1

[0038] This example prepares a high-nickel ternary precursor, and the specific process is as follows:

[0039] S1: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a 1.6 mol / L metal salt solution according to a metal molar ratio of 0.82:0.12:0.06 for later use;

[0040] S2: Seed preparation: pure water was added to the seed kettle, nitrogen was introduced, stirring and heating were started, the speed was 220 rpm, the temperature was 65 ° C, the ammonia concentration was 7.0 g / L, alkali solution was introduced to adjust the pH to 11.6, and then alkali solution and metal salt solution were introduced at the same time for precipitation reaction. The environment in the kettle was kept constant during the feeding process, and the clear liquid in the kettle was filtered out through a microporous filter device to keep the liquid level in the kettle constant. The feeding was continued, the material in the kettle was continuously concentrated, and the particles continued to grow until the particle size grew to 3.0 μm. After the feeding was completed, the precursor seed crystal preparation was completed, and the prepared precursor seed crystal was placed in the seed tank for standby use;

[0041] S3: Precursor growth (growth with seed crystals): Add two-thirds of the volume of pure water to the reactor, introduce nitrogen, start stirring and heating, with a stirring speed of 180 rpm and a temperature of 65°C, introduce ammonia water to make the ammonia concentration in the reactor reach 6.0 g / L, then introduce alkali solution to adjust the pH value in the reactor to 11.5, inject one-third of the volume of seed crystals into the reactor, and then introduce alkali solution and metal salt solution at the same time. The metal ions precipitate on the seed crystals to grow the seed crystal particles, and continue feeding. During the feeding process, the pH value in the reactor is kept constant, and the ammonia concentration, stirring speed and temperature in the reactor are kept constant. After the reactor is full, the material flows out through the overflow port. At this time, the overflowed material is treated as a defective product and scrapped, and the particles in the reactor continue to grow;

[0042] S4: Particle size adjustment and material collection: When the particle size in the reactor grows to D50 of 10.5 μm, seed crystals are introduced. After the seed crystals are introduced, the particle size of the material in the reactor decreases until the particle size D10 drops to 4.0, and the introduction is stopped. Due to the continuous introduction of alkali solution and metal salt solution, the seed crystals and the previous particles continue to grow, and the overflowed material is collected in the aging tank. When the particle size D50 in the reactor grows to 10.5 μm again, seed crystals are introduced again to reduce the particle size. The above operation is repeated continuously. The particle size in the reactor is kept in dynamic balance by intermittently introducing seed crystals, and the particle size is always kept within the target range. The particle size D50 of this embodiment can be maintained at about 10.0 μm, and the overflowed material is continuously collected. The collected material is washed, dried, and sieved to obtain the final high-nickel ternary precursor product Ni 0.82 Co 0.12 Mn 0.06 (OH)2.

[0043] Example 2

[0044] This example prepares a high-nickel ternary precursor, and the specific process is as follows:

[0045] S1: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a 1.8 mol / L metal salt solution according to a metal molar ratio of 0.90:0.07:0.03 for later use;

[0046] S2: Seed preparation: pure water was added to the seed kettle, nitrogen was introduced, stirring and heating were started, the speed was 240 rpm, the temperature was 70°C, the ammonia concentration was 5.0 g / L, alkali solution was introduced to adjust the pH to 12.0, and then alkali solution and metal salt solution were introduced at the same time for precipitation reaction. During the feeding process, the environment in the kettle was kept constant, the clear liquid in the kettle was filtered out through a microporous filter device to keep the liquid level in the kettle constant, the feeding was continued, the material in the kettle was continuously concentrated, and the particles continued to grow until the particle size grew to 4.0 μm. After the feeding was completed, the precursor seed crystal preparation was completed, and the prepared precursor seed crystal was placed in the seed tank for standby use;

[0047] S3: Precursor growth (direct growth): Add two-thirds of the volume of pure water to the reactor, introduce nitrogen, start stirring and heating, with a stirring speed of 220 rpm and a temperature of 70°C, introduce ammonia water to make the ammonia concentration in the reactor reach 5.0 g / L, then introduce alkali solution to adjust the pH value in the reactor to 12.2, then introduce alkali solution and metal salt solution simultaneously for precipitation reaction, and continue feeding. During the feeding process, the pH value in the reactor is kept constant, and the ammonia concentration, stirring speed and temperature in the reactor are kept constant. After the reactor is full, the material flows out through the overflow port. At this time, the overflowed material is scrapped as unqualified products, and the particles in the reactor continue to grow;

[0048] S4: Particle size adjustment and material collection: When the particle size in the reactor grows to D50 of 10.0 μm, seed crystals are introduced. After the seed crystals are introduced, the particle size of the material in the reactor decreases until the particle size D10 drops to 4.0 and the introduction is stopped. Due to the continuous introduction of alkali solution and metal salt solution, the seed crystals and the previous particles continue to grow, and the overflowed material is collected in the aging tank. When the particle size D50 in the reactor grows to 10.0 μm again, seed crystals are introduced again to reduce the particle size. The above operation is repeated continuously. The particle size in the reactor is kept in dynamic balance by intermittently introducing seed crystals, and the particle size is always kept within the target range. The particle size D50 of this embodiment can be maintained at about 9.8 μm. The overflowed material is continuously collected, and the collected material is washed, dried, and sieved to obtain the final high-nickel ternary precursor product Ni 0.90 Co 0.07 Mn 0.03 (OH)2.

[0049] Comparative Example 1

[0050] This comparative example prepares a high-nickel ternary precursor. The difference from Example 2 is that no seed crystals are added to adjust the particle size. The specific process is as follows:

[0051] S1: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a 1.8 mol / L metal salt solution according to a metal molar ratio of 0.90:0.07:0.03 for later use;

[0052] S2: Add two-thirds of the volume of pure water to the reactor, introduce nitrogen, start stirring and heating, with a stirring speed of 220 rpm and a temperature of 70°C, introduce ammonia water to make the ammonia concentration in the reactor reach 5.0 g / L, then introduce alkali solution to adjust the pH value in the reactor to 12.2, then introduce alkali solution and metal salt solution simultaneously for precipitation reaction, and continue feeding. During the feeding process, the pH value in the reactor is kept constant, and the ammonia concentration, stirring speed and temperature in the reactor are kept constant. After the reactor is full, the material flows out through the overflow port. At this time, the overflowed material is scrapped as unqualified products, and the particles in the reactor continue to grow;

[0053] S3: When the particle size in the reactor grows to D50 of 10.0 μm, the material in the reactor is made into small particles by increasing the pH value or increasing the stirring speed to reduce the particle size, and the D50 is controlled to be maintained at about 10.0 μm. The material in the reactor overflows into the aging tank, and then is washed, dried, and sieved to obtain the final high-nickel ternary precursor product Ni 0.90 Co 0.07 Mn 0.03 (OH)2.

[0054] Comparative Example 2

[0055] This comparative example is a commercialized 811 precursor produced by Guangdong Brunp Recycling Technology Co., Ltd.

[0056] Test example

[0057] This test example tested the particle size, tap density (TD) and compacted density (CD) of the precursors of Example 1-2 and Comparative Example 1-2. The results are shown in Table 1 below.

[0058] Table 1

[0059] Sample D10 (μm) D50 (μm) D90 (μm) TD (g / cm 3 )CD(g / cm 3 ) Example 14.3510.0518.572.123.46 Example 24.239.8619.022.153.49 Comparative Example 16.3310.1016.521.983.12 Comparative Example 25.8510.2816.022.073.18

[0060] According to the data in Table 1, the average particle size D50 of Examples 1-2 and Comparative Examples 1-2 is about 10 μm, but the D10 of Examples 1 and 2 is smaller than that of Comparative Examples 1-2, while the D90 is greater than that of Comparative Examples 1-2, indicating that the particle size distribution of the Examples is broader. The tap density (TD) and compacted density (CD) of the Examples are significantly greater than those of the Comparative Examples, indicating that the precursor particle size distribution and particle strength of the Examples of the present invention have a significant improvement in increasing the tap density and compacted density of the particles.

[0061] Figure 1 is a process flow chart of the present invention. Precursor seed crystals are first prepared in a seed kettle and injected into a seed tank for standby use. The precursor seed crystals are mainly used to adjust the particle size of the precursor in the reactor. The precursor grows in the reactor and the particle size is adjusted by the seed crystals. After reaching the target particle size, the overflowed material is collected into an aging tank, and then filtered, washed, dried, sifted, and processed to obtain the final precursor product.

[0062] Figure 2 shows the compaction density curves of Examples 1 and 2 and the comparative example precursors. To verify the material's cracking resistance, the precursors were subjected to a pressure cracking test on a compaction density meter with a maximum yield strength set to 380 MPa. As shown in Figure 2, under the same pressure, the precursors obtained in Examples 1 and 2 have a higher compaction density than the conventional precursor samples, indicating that the precursor particles in Examples 1 and 2 have a higher bulk density and better pressure resistance. The compaction transition points of Examples 1 and 2 are 18.04 MPa and 16.08 MPa, respectively, both much higher than the comparative example's compaction transition point of 13.20 MPa, indicating that Examples 1 and 2 have much higher pressure cracking resistance than the comparative example precursor.

[0063] FIG3 is an SEM image of the precursor of Example 1. It can be seen from the image that the precursor particles are regular spherical and the crystals on the particle surface are evenly and densely distributed.

[0064] Figure 4 is a cross-sectional SEM image of the precursor from Example 1. This cross-sectional image shows that the particles are composed of fine primary grains, with numerous and evenly distributed grain boundaries and appropriate porosity within the particles. This internal structure with multiple grain boundaries and appropriate porosity, coupled with a wide particle size distribution, is the primary reason for their excellent crack resistance.

[0065] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a high-nickel ternary precursor, characterized in that: The following steps are involved: S1: preparing a metal salt solution of nickel salt, cobalt salt and manganese salt; S2: Under an inert atmosphere, heating and introducing ammonia water, then introducing alkali solution to adjust the pH, and then introducing alkali solution and the metal salt solution simultaneously to carry out a precipitation reaction to obtain particles with a D50 of 7.0 to 15.0 μm; S3: When the D10 of the particles is adjusted to 2.0-7.0 μm by introducing seed crystals, the seed crystal introduction is stopped, the alkali solution and the metal salt solution are continuously introduced, and the overflowed material is collected. When the particle size grows to a D50 of 7.0-15.0 μm, the seed crystal addition operation is repeated, and the overflowed material is continuously collected; S4: washing, drying and sieving the collected materials to obtain the high-nickel ternary precursor.

2. The preparation method according to claim 1, characterized in that The method also includes a preparation process of the seed crystals: adding water to a seed crystal reactor, introducing an inert gas, starting stirring and heating, introducing ammonia water, introducing an alkali solution to adjust the pH, and then introducing the alkali solution and the metal salt solution at the same time for a precipitation reaction, continuously feeding, filtering out the clear liquid from the seed crystal reactor to maintain a constant liquid level, continuously concentrating the material, and continuously growing the particles until the particle size grows to 2.0 to 7.0 μm, stopping feeding, and obtaining the seed crystals.

3. The preparation method according to claim 1, characterized in that In step S2, after adjusting the pH, seed crystals are first added, and then alkali solution and metal salt solution are introduced simultaneously to perform precipitation reaction, wherein the particle size of the seed crystals is 2.0 to 7.0 μm.

4. The preparation method according to claim 1, characterized in that In step S4, the general structural formula of the high nickel ternary precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.6<x<1, 0<y<0.4, x+y<1.

5. The preparation method according to claim 1, characterized in that In step S4, the particle size D10 of the high-nickel ternary precursor is 2.0-7.0 μm, D50 is 7.0-15.0 μm, and D90 is 12.0-20.0 μm.

6. The preparation method according to claim 1, characterized in that In step S2, the precipitation reaction is continuously stirred throughout the entire process, and the stirring speed is 150-250 rpm.

7. The preparation method according to claim 1, characterized in that In step S2, the heating temperature is 50-80°C.

8. The preparation method according to claim 1, characterized in that In step S2, the concentration of the ammonia water is 0-10 g / L.

9. The preparation method according to claim 1, characterized in that In step S2, the pH is adjusted to 11.0-13.

0.

10. Use of the preparation method according to any one of claims 1 to 9 in the preparation of lithium ion batteries.