CN110127777A - A kind of wet-process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor and its preparation method - Google Patents

Abstract

A wet process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor and a preparation method thereof, the general chemical formula of the nickel-cobalt-aluminum ternary precursor is Ni _x CoyAl _z (OH) ₂ , where x+y+z=1 , and 0.3≤x≤0.9, 0.01≤y≤0.4, 0.01≤z≤0.4, the Zr element accounts for 0.001%‑3% of the total mass of the nickel-cobalt hydroxide precursor; the ternary precursor consists of three layers, and the The layer is a zirconium-doped nickel-cobalt binary precursor, the molecular formula is: Ni _x Co _y (OH) ₂ , and the outer layer is a zirconium-doped nickel-cobalt-aluminum ternary precursor, the molecular formula is: Ni _x Co _y Al _z (OH) ₂ , the intermediate layer is a concentration gradient precursor between the zirconium-doped nickel-cobalt binary precursor and the zirconium-doped nickel-cobalt-aluminum ternary precursor, and the present invention also includes the preparation method of the nickel-cobalt-aluminum ternary precursor. The zirconium-doped nickel-cobalt-aluminum ternary precursor of the present invention has narrow particle size distribution and good particle morphology; the complexation controls the crystallization co-precipitation to make the doping elements uniform, and the positive electrode precursor prepared by using it has high specific capacity, good cycle stability and processing performance. Well, stable performance.

Description

A kind of wet-process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor and its preparation method

technical field

The invention relates to the technical field of manufacturing a zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor, in particular to a wet-process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor and a preparation method thereof.

Background technique

As a new type of green battery, lithium-ion batteries have many advantages such as high voltage, specific energy, and low environmental pollution. They have been widely used in the field of digital products, and are gradually expanding to the fields of electric vehicles, satellites, and aerospace. High energy and high density are the development direction of lithium-ion power batteries in the future. As an important material that affects the performance of lithium-ion power batteries, the research and development of positive electrode precursors has become the focus of the industry.

Lithium-ion power batteries have high requirements on the positive electrode precursor, which requires a large energy density, good cycle life and relatively low price. Traditional positive electrode precursors, such as nickel-cobalt lithium manganese oxide positive electrode precursors, have high specific capacity, but the activity and cycle performance of the precursor are poor, and the high temperature resistance is not enough, which can no longer meet the needs of lithium-ion power batteries. The nickel-cobalt-aluminum ternary cathode has low cost, high specific capacity and cycle stability, and has become a recent research hotspot in the industry. The industrialized preparation of nickel-cobalt-aluminum ternary positive electrode materials adopts solid-phase doping of aluminum elements. Generally, nickel-cobalt or nickel-cobalt-manganese hydroxides are prepared first, and then the precursors are mixed with lithium salts and small-particle aluminum compounds. High-temperature treatment is difficult to achieve Homogenize.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art, and provide a wet-process zirconium-doped concentration-gradient nickel-cobalt-aluminum ternary precursor and a preparation method thereof.

The technical solution adopted by the present invention to solve the technical problem is a wet-process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor whose general chemical formula is Ni _x CoyAl _z (OH) ₂ , where x+y+z=1 , and 0.3≤x≤0.9, 0.01≤y≤0.4, 0.01≤z≤0.4, the Zr element accounts for 0.001%-3% of the total mass of the nickel-cobalt hydroxide precursor; the ternary precursor consists of three layers, The inner layer is a zirconium-doped nickel-cobalt binary precursor, the molecular formula is: Ni _x Co _y (OH) ₂ , and the outer layer is a zirconium-doped nickel-cobalt-aluminum ternary precursor, the molecular formula is: Ni _x Co _y Al _z (OH) ) ₂ , wherein the middle layer is a concentration gradient precursor between the zirconium-doped nickel-cobalt binary precursor and the zirconium-doped nickel-cobalt-aluminum ternary precursor.

The preparation method of the nickel-cobalt-aluminum ternary precursor with a concentration gradient doped with zirconium in a wet process of the present invention comprises the following steps:

Step 1, preparing nickel-cobalt-zirconium soluble salt solution, sodium hydroxide aqueous solution, ammonia solution and sodium metaaluminate solution; Step 2, adding the nickel-cobalt-zirconium soluble salt solution prepared in step 1 and the Said sodium hydroxide aqueous solution, according to the molar ratio of Ni:Co 0.80:0.15 preparation total concentration is the nickel-cobalt soluble salt solution of 2.0mol/L, zirconium salt is the 0.3% zirconium sulfate solution of nickel-cobalt hydroxide gross mass, prepares Generate zirconium-doped nickel-cobalt hydroxide crystal nuclei; step 3, continue to add the nickel-cobalt-zirconium soluble salt solution and sodium hydroxide solution prepared in step 1 to the reaction kettle, and pump ammonia solution at the same time to prepare the inner layer It is a small particle of zirconium-doped nickel-cobalt binary precursor; step 4, further adding the nickel-cobalt-zirconium soluble salt solution, the sodium hydroxide aqueous solution, and the ammonia solution prepared in step 1 to the reaction kettle, and simultaneously pumping Sodium metaaluminate solution to prepare a ternary precursor whose outer layer is a zirconium-doped nickel-cobalt-aluminum ternary precursor; step 5, centrifuge washing the solid particle material of the reaction product obtained in step 4, then centrifugal dehydration, and then dry and sieving to obtain a nickel-cobalt-aluminum ternary precursor doped with a concentration gradient of zirconium, which is sealed and preserved.

Further, in step 1, the concentration of the prepared nickel-cobalt-zirconium soluble salt solution is 2-2.5mol/L, the concentration of the sodium hydroxide aqueous solution is 8-10mol/L, and the zirconium salt solution is nickel-cobalt 0.001%-5% of the total mass of hydroxide, the concentration of the ammonia solution is 8-10mol/L, and the concentration of the sodium metaaluminate solution is 0.3-0.9mol/L.

Further, in step 1, the prepared nickel-cobalt-zirconium soluble salt solution is nickel, cobalt, and zirconium sulfate solution, and the sodium metaaluminate solution is prepared by dissolving aluminum sulfate solid in excess sodium hydroxide solution.

Further, in step three, the particle size of the small particles of the zirconium-doped nickel-cobalt binary precursor is 3.5-5.5 μm; in the step four, the shape of the ternary precursor is spherical or spherical, and its particle size is 10.5-11.5 μm.

Further, the reaction kettle is a reaction kettle equipped with a temperature-controlled water bath jacket, a stirring paddle and a precision filter tube, and a mother liquor is added to the reaction kettle. The mother liquor has an ammonia concentration of 0.15-0.25mol/L and a pH=11.5-12.0. The above mother liquor is not passed through all the stirring paddles of the reaction kettle; after the material in the reaction kettle is full, the excess mother liquor is discharged out of the reaction kettle through a precision filter tube, and the solid content in the reaction system is controlled to 450-650g/L.

Further, the preparation method of the wet-process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor is characterized in that, in step 2, nitrogen gas is introduced into the sealed reaction kettle, and the amount of nitrogen gas introduced is 1% of the volume of the reaction kettle. /200～1/100, start stirring, use 8-10mol/L sodium hydroxide aqueous solution to adjust the pH of the bottom liquid to 12.5-13.0; adjust the stirring speed to 400-500r/min, use a precision metering pump to control the salt solution The flow rate is 80-120L/h, the temperature of the reactor is controlled at 50-65°C, and the feeding time is 3-5 hours. When the pH drops to 11.8-12.5, zirconium-doped nickel-cobalt hydroxide crystal nuclei are formed.

Further, the volume of the reaction kettle is 5000-7000L.

Further, in step 3, the precision metering pump controls the flow rate of the saline solution to 80-120 L/h, controls the ammonia concentration to 0.25-0.35 mol/L, and adjusts the flow rate of the aqueous sodium hydroxide solution to control the pH of the reaction solution to 11.8-12.5, Control reaction temperature is 55-65 ℃.

Further, the stirring speed of the reactor is adjusted to 500-700r/min, the precision metering pump keeps the flow rate of the nickel-cobalt salt solution constant, the flow rate of the sodium metaaluminate solution is increased at a uniform speed, the flow rate of the aqueous sodium hydroxide solution is adjusted, and the pH of the reaction solution is controlled. 11.1-11.4, control the reaction temperature at 55-65°C.

Further, in Step 5, the temperature of the pure water used for washing is 55-80° C., and the washing is stopped when Na+ in the material is ≤0.0150%, the drying temperature is 100-130° C., and the sieving is performed with a 200-mesh screen.

Further, in the second step, nitrogen gas is passed into the sealed reaction kettle, the nitrogen gas is 1/200 to 1/100 of the volume of the reaction kettle, stirring is started, and the bottom liquid is mixed with the 8-10mol/L sodium hydroxide aqueous solution Adjust the pH to 12.5-13; adjust the stirring speed to 400-500r/min, use a precision metering pump to control the salt flow to 80-120L/h, control the temperature of the reactor to 50-65°C, and the feeding time to 3-5 hours , when the pH drops to 11.8-12.5, zirconium-doped nickel-cobalt hydroxide crystal nuclei are formed.

Further, the precision metering pump in step three controls the salt flow rate to 80-120 L/h, controls the ammonia concentration to 0.25-0.35 mol/L, and adjusts the flow rate of the aqueous sodium hydroxide solution to control the pH of the reaction solution to 11.8-12.5, Control the temperature of the reactor to be 55-65°C.

Further, in step 4, the stirring speed of the reactor is adjusted to 500-700r/min, the precision metering pump keeps the flow rate of the nickel-cobalt salt constant, the flow rate of the sodium metaaluminate solution is increased at a uniform speed, the flow rate of the aqueous sodium hydroxide solution is adjusted, and the flow rate of the reaction solution is controlled. pH=11.1-11.4, control the temperature of the reactor at 55-65°C.

Further, the temperature of the pure water used for washing in step 5 is 55-80°C, and the washing is stopped when Na+ in the material is ≤0.0150%, the drying temperature is 100-130°C, and the sieving is carried out with a 200-mesh screen.

The wet-process zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor prepared by using the positive electrode precursor has high capacity, good cycle stability, good processability and stable performance.

The principle of the preparation method of the present invention is that the co-precipitation method of complexation controlled crystallization is adopted, and the soluble salt solution of nickel, cobalt and zirconium in the reactor and the aqueous solution of sodium hydroxide are subjected to co-precipitation reaction under the complexation of ammonia, and the small particles are first prepared. Zirconium-nickel-cobalt binary hydroxide, and then add sodium metaaluminate solution to the reaction kettle, the optimal solution is to gradually increase the flow rate of sodium metaaluminate solution, and at the same time increase the solid-liquid ratio and continue the reaction to grow to the required particle size , the obtained zirconium-doped nickel-cobalt-aluminum ternary precursor changes in a uniform gradient from the inner core to the outer metal ratio; increasing the solid-liquid ratio of the reactor solution results in a narrow particle size distribution and good particle morphology of the ternary precursor; complexation Controlling the crystallization co-precipitation makes the doping elements uniform, so that the subsequent positive electrode precursor prepared by using it has high specific capacity, good cycle stability, good processing performance and stable performance.

Description of drawings

Fig. 1 is the morphology diagram of the nickel-cobalt-aluminum ternary precursor doped with zirconium concentration gradient obtained in Example 1 of the present invention under a 1000 times electron microscope;

Fig. 2 is the topography of the zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor obtained in Example 1 of the present invention under a 5000 times electron microscope;

Fig. 3 is a morphological view of the zirconium-doped concentration-gradient nickel-cobalt-aluminum ternary precursor obtained in Example 1 of the present invention under a 10,000-times electron microscope.

Fig. 4 is the CR2025 button battery assembled with the positive electrode of the battery made by using the positive electrode precursor made by the product of Example 1 of the present invention and the battery positive assembled CR2025 button battery made of the positive electrode precursor made by the corresponding product of Comparative Example 1. Performance comparison chart.

Detailed ways

Below in conjunction with embodiment the specific embodiment of the present invention is described in further detail:

In the embodiment of the present invention, the nickel-cobalt-aluminum ternary precursor doped with zirconium concentration gradient in wet method has a general chemical formula of Ni _0.80 Co _0.15 Al _0.05 (OH) ₂ : d10=6.26um, d50=10.47um, d90=18.62um, vibration Solid density=1.69g/cm ³ , specific surface area=20.31m ² /g. As shown in Figure 1-3, the morphology is spherical or spherical.

The embodiment of the preparation method of the nickel-cobalt-aluminum ternary precursor with a concentration gradient doped with zirconium in the present invention comprises the following steps:

Step 1: Prepare a nickel-cobalt soluble salt solution with a total concentration of 2.0mol/L according to the molar ratio of Ni:Co 0.80:0.15. The zirconium salt is a 0.3% zirconium sulfate solution of the total mass of nickel-cobalt hydroxide. Mix the dissolved salt solution with the zirconium salt solution, prepare an aqueous sodium hydroxide solution with a concentration of 8 mol/L, prepare an aqueous ammonia solution with a concentration of 10 mol/L, and prepare a sodium metaaluminate solution with a concentration of 0.6 mol/L; sodium metaaluminate solution It is obtained by dissolving solid aluminum sulfate in excess sodium hydroxide solution.

Step 2: Add the mother liquor with ammonia concentration of 0.15mol/L and pH=11.78 into the 6500L reaction kettle equipped with temperature-controlled water bath jacket, stirring paddle and precision filter tube as the bottom liquid, and make the bottom liquid not pass through the reaction kettle All stirring paddles, the mother liquor is pure water at 55°C, adding ammonia water and sodium hydroxide solution to make the concentration of ammonia water 0.15mol/L, pH=11.78;

Introduce nitrogen into the sealed reaction kettle, the nitrogen flow rate is 2L/min, start stirring, the rotation speed is 400r/min, and adjust the pH of the bottom liquid to 12.9 with 8mol/L sodium hydroxide aqueous solution;

Start the production of crystal nuclei: adjust the stirring speed of the reactor to 500r/min, and use a precision metering pump to add 2.0mol/L nickel-cobalt-zirconium soluble salt solution and 8mol/L sodium hydroxide aqueous solution into the reactor in parallel to control the salt concentration. The flow rate of the aqueous solution is 120L/h, and the reaction temperature is controlled at 55°C. With continuous feeding, when the pH drops to 11.8 after 3 hours, nickel-cobalt-manganese hydroxide crystal nuclei are formed, and the crystal nucleation stage is completed;

Step 3: Add 2.0 mol/L nickel-cobalt-zirconium soluble salt solution, 8 mol/L sodium hydroxide solution, and 10 mol/L ammonia solution into the reaction kettle in parallel with a precision metering pump, and control the flow rate of the salt solution to 120L /h, adjust the flow rate of aqueous sodium hydroxide solution, control the pH=11.85 of the reaction solution, and control the reaction temperature to be 55°C;

As the feeding continues, the small crystal nuclei grow gradually and the sphericity tends to be perfect. After the reactor is filled with the reaction materials, the slurry enters the aging reactor, and the crystals in the reactor continue to crystallize and grow;

Use a laser particle size analyzer to detect the particle size of the solid particle material obtained from the reaction once every hour. When it is detected that the median particle size of the small particles of nickel-cobalt-manganese hydroxide in the reactor reaches 4.0±0.5μm, stop feeding ;

The excess mother liquor is discharged out of the reaction kettle through a precision filter tube, and the solid content in the reaction system is controlled to 500g/L;

Step 4: Adjust the stirring speed of the reactor to 700r/min, add 2.0mol/L nickel-cobalt-zirconium soluble salt solution, 8mol/L sodium hydroxide aqueous solution, and 10mol/L ammonia solution into the reactor with a precision metering pump, and control The flow rate of the salt solution is 120L/h. Use a precision metering pump to add 0.6mol/L sodium metaaluminate aqueous solution into the reactor in parallel. The initial flow rate of the sodium metaaluminate solution is 4L/h, and at the same time increase the Increase the flow rate of sodium metaaluminate solution, control the reaction temperature at 55°C, keep the flow rate of salt solution and sodium metaaluminate solution constant after 8 hours as the feed continues, and adjust the sodium hydroxide aqueous solution in real time by measuring the pH Flow rate, control the pH of the reaction solution to 11.4, continue the reaction, the crystal nucleus grows gradually, and the sphericity tends to be perfect. After the reactor is filled with the reaction material, the excess mother liquor is discharged from the reactor through a precision filter tube to control the solid content in the reaction system It is 500g/L, and the crystal in the reactor stays in the reactor and continues to crystallize and grow up;

Use a laser particle size analyzer to detect the particle size of the solid particle material in the reaction kettle once in 1 hour. When it is detected that the median particle size of the granular nickel-cobalt-manganese hydroxide in the reaction kettle reaches 10.5-11.5 μm, stop feeding and put The rotating speed of the stirring paddle in the reaction kettle was adjusted to 200r/min, and the stirring and aging were continued for 2 hours;

Step 5: After the aging of the reaction kettle, wash the solid particle material of the reaction product in the reaction kettle with a centrifuge, and control the temperature of the pure water for washing at 70°C until Na+≤0.0150% in the solid particle material of the reaction product, then stop washing , dehydrated with a centrifuge; dried the dehydrated solid particle material; sieved through a 200-mesh sieve to obtain a zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor, which can be sealed and stored.

Weigh 5kg of the ternary precursor obtained in step 5 and 2.2kg of lithium hydroxide monohydrate into a high-speed mixer for mixing, and after mixing evenly, put them into a box-type resistance furnace for sintering; ℃ heat treatment for 3 hours, then 630 ℃ heat treatment for 5 hours, and finally 770-780 ℃ heat treatment for 10 hours, keeping an oxygen atmosphere throughout the process, the obtained product was dissociated, sieved, and finally obtained a zirconium-doped concentration gradient nickel-cobalt-aluminum ternary positive electrode material.

The morphology of the obtained zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor is shown in Figures 1, 2, and 3. It can be seen from Figures 1, 2, and 3 that the particles of the nickel-cobalt-aluminum ternary precursor with concentration gradient doped with zirconium prepared by the present invention are mostly spherical or ellipsoidal in shape.

Take the zirconium-doped concentration gradient nickel-cobalt-aluminum ternary positive electrode material, mix it evenly with carbon black and PVDF, coat it on aluminum foil to make a positive electrode sheet, and assemble it with a lithium metal sheet, a diaphragm, and an electrolyte in a vacuum glove box to form a CR2025 button-type Battery.

The electrical properties of the CR2025 button battery were tested: the 0.1C discharge capacity was 207.35 mA/g, the 1C discharge capacity was 186.55 mA/g, and the capacity retention rate after 50 cycles of 1C cycle was 99.51%.

Comparative example 1

According to the molar ratio of Ni:Co:Mn 0.80:0.15:0.05, the nickel-cobalt-manganese soluble salt solution with a total concentration of 2.0mol/L is prepared, the zirconium salt is 0.3% zirconium sulfate solution of the total mass of nickel-cobalt hydroxide, and the nickel The cobalt-manganese soluble salt solution is mixed with the zirconium salt solution to prepare an aqueous sodium hydroxide solution with a concentration of 8 mol/L and an aqueous ammonia solution with a concentration of 10 mol/L.

Add the mother liquor with ammonia concentration of 0.15mol/L and pH=11.78 into the 6500L reactor equipped with a temperature-controlled water bath jacket, stirring paddle and precision filter tube as the bottom liquid, and make the bottom liquid pass through all the stirring paddles in the reactor , the mother liquor is pure water at 55°C, adding ammonia water and sodium hydroxide solution to make the concentration of ammonia water 0.15mol/L, pH=11.78;

Introduce nitrogen into the sealed reaction kettle, the nitrogen flow rate is 2L/min, start stirring, the rotation speed is 400r/min, and adjust the pH of the bottom liquid to 12.9 with 8mol/L sodium hydroxide aqueous solution;

Start the production of crystal nuclei: adjust the stirring speed of the reactor to 500r/min, and add 2.0mol/L nickel-cobalt-manganese-zirconium soluble salt solution and 8mol/L sodium hydroxide aqueous solution into the reactor with a precision metering pump, and control The flow rate of the brine solution is 120L/h, and the reaction temperature is controlled at 55°C. With continuous feeding, when the pH drops to 11.8 after 3 hours, nickel-cobalt-manganese hydroxide crystal nuclei are formed, and the crystal nucleation stage is completed;

Step 3: Add 2.0mol/L nickel-cobalt-manganese-zirconium soluble salt solution, 8mol/L sodium hydroxide solution, and 10mol/L ammonia solution into the reaction kettle in parallel with a precision metering pump, and control the flow of the salt solution to 120L/h, adjust the flow rate of aqueous sodium hydroxide solution, control the pH of the reaction solution to 11.85, and control the reaction temperature to 55°C;

As the feeding continues, the small crystal nuclei grow gradually and the sphericity tends to be perfect. After the reactor is filled with the reaction materials, the slurry enters the aging reactor, and the crystals in the reactor continue to crystallize and grow;

Use a laser particle size analyzer to detect the particle size of the solid particle material obtained by one reaction in one hour. When it is detected that the median particle size of the small particles of nickel-cobalt-manganese hydroxide in the reactor reaches 3.5-5.5 μm, stop feeding;

The excess mother liquor is discharged out of the reaction kettle through a precision filter tube, and the solid content in the reaction system is controlled to 500g/L;

Step 4: Adjust the stirring speed of the reactor to 700r/min, add 2.0mol/L nickel-cobalt-manganese-zirconium soluble salt solution, 8mol/L sodium hydroxide aqueous solution, and 10mol/L ammonia solution into the reactor with a precision metering pump, Control the flow rate of the salt solution to 120L/h, and control the reaction temperature to 55°C. With the continuous feeding, control the pH of the reaction solution to 11.4, continue the reaction, the crystal nuclei grow gradually, the sphericity tends to be perfect, and the reactor is reacted After the material is full, the excess mother liquor is discharged from the reactor through a precision filter tube, and the solid content in the reaction system is controlled to 500g/L, and the crystals in the reactor remain in the reactor to continue to crystallize and grow;

Use a laser particle size analyzer to detect the particle size of the solid particle material in the reaction kettle once in 1 hour. When it is detected that the median particle size of the granular nickel-cobalt-manganese hydroxide in the reaction kettle reaches 10.5-11.5 μm, stop feeding and put The rotating speed of the stirring paddle in the reaction kettle was adjusted to 200r/min, and the stirring and aging were continued for 2 hours;

Step 5: After the aging of the reaction kettle, wash the solid particle material of the reaction product in the reaction kettle with a centrifuge, and control the temperature of the pure water for washing at 70°C until Na+≤0.0150% in the solid particle material of the reaction product, then stop washing , dehydrated with a centrifuge; dried the dehydrated solid particle material; sieved through a 200-mesh sieve to obtain a zirconium-doped concentration gradient nickel-cobalt-aluminum ternary precursor, which can be sealed and stored.

Weigh 5kg of the ternary precursor obtained in step 5 and 2.2kg of lithium hydroxide monohydrate into a high-speed mixer for mixing, and after mixing evenly, put them into a box-type resistance furnace for sintering; ℃ heat treatment for 3 hours, then 630 ℃ heat treatment for 5 hours, and finally 770-780 ℃ heat treatment for 10 hours, keeping an oxygen atmosphere throughout the process, the obtained product was dissociated, sieved, and finally obtained a zirconium-doped nickel-cobalt-manganese ternary positive electrode material.

The positive electrode material was mixed with carbon black and PVDF evenly, coated on aluminum foil to make a positive electrode sheet, and assembled into a CR2025 button battery with a lithium metal sheet, a diaphragm, and an electrolyte in a vacuum glove box.

The electrical properties of the CR2025 button battery were tested, and the 0.1C discharge capacity was 203.46 mA/g, the 1C discharge capacity was 181.98 mA/g, and the capacity retention rate after 50 cycles of 1C cycle was 92.87%.

Figure 4 is a comparison of the electrical properties of the positive assembled CR2025 button battery made by using the positive electrode precursor made by the product of Example 1 of the present invention and the positive assembled CR2025 button battery made by the positive precursor made by the corresponding product of Comparative Example 1 picture.

It can be seen from Fig. 4 that in the voltage range of 3.0-4.3V and at a normal temperature of 25°C, the capacity, rate and cycle performance of the test sample of the embodiment of the present invention are obviously better than those of the comparative test sample.

The content not described in detail in the description is the prior art known to those skilled in the art.

The above descriptions are only preferred embodiments of the present invention. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims (10)

1. a kind of wet process mixes zirconium concentration gradient nickel cobalt aluminium ternary precursor, which is characterized in that its chemical general formula is Ni_xCo_yAl_z (OH)₂, wherein x+y+z=1, and 0.3≤x≤0.9,0.01≤y≤0.4,0.01≤z≤0.4, Zr element accounts for nickel cobalt hydrogen-oxygen The 0.001%-3% of compound presoma gross mass；The ternary precursor consists of three layers, and internal layer is before mixing zirconium nickel cobalt binary Drive body, molecular formula are as follows: Ni_xCo_y(OH)₂, outer layer is to mix zirconium nickel cobalt aluminium ternary precursor, molecular formula are as follows: Ni_xCo_yAl_z(OH)₂, Wherein interbed mixes zirconium nickel cobalt binary presoma and mixes the concentration gradient presoma between zirconium nickel cobalt aluminium ternary precursor to be described.

2. a kind of wet process as described in claim 1 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, feature It is, comprising the following steps: Step 1: preparing nickel cobalt zirconium metal mixed salt solution, sodium hydroxide solution, ammonia spirit, inclined aluminium Acid sodium solution and reaction kettle bottom liquid；Step 2: adding the nickel cobalt zirconium metal salt mixing prepared in step 1 in a kettle Solution and the sodium hydroxide solution, preparing total concentration by Ni: Co molar ratio 0.80: 0.15 can for the nickel cobalt of 2.0mol/L Salt solution, zirconates are 0.3% sulfuric acid zirconium solution of nickel cobalt hydroxide gross mass, and preparation, which generates, mixes zirconium nickel cobalt hydroxide crystalline substance Core；Step 3: continuing to add the nickel cobalt zirconium metal mixed salt solution, the hydrogen-oxygen prepared in step 1 in a kettle Change sodium solution, and add ammonia spirit, preparation generates fine granularity and mixes zirconium nickel cobalt binary presoma；Step 4: in a kettle The nickel cobalt zirconium metal mixed salt solution, the sodium hydroxide solution, ammonia spirit prepared in step 1 are further added, and is added Sodium aluminate solution, ultimately generating nucleus is to mix zirconium nickel cobalt hydroxide, and the internal layer for wrapping up nucleus is to mix zirconium nickel cobalt binary forerunner Body, outer layer are to mix zirconium nickel cobalt aluminium ternary precursor, mix zirconium nickel cobalt binary presoma internal layer and mix outside zirconium nickel cobalt aluminium ternary precursor The large grained ternary precursor of middle layer concentration gradient presoma between layer；Step 5: the reaction of step 4 is completed Large grained ternary precursor carries out centrifuge washing, is then centrifuged for being dehydrated, then dry, sieve, and finally sealed saves.

3. wet process according to claim 2 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, feature exists In in step 1, the concentration of the nickel cobalt zirconium metal mixed salt solution of preparation is 2.0-2.5mol/L, and wherein zr element is nickel The 0.001%-5% of cobalt hydroxide gross mass, the concentration of the sodium hydroxide solution are 8-10mol/L, the ammonia spirit Concentration is 8-10mol/L, and the concentration of the sodium aluminate solution is 0.3-0.9mol/L.

4. wet process according to claim 2 or 3 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, feature It is, in step 1, the nickel cobalt zirconium metal mixed salt solution of preparation is the sulfate liquor of nickel, cobalt, zirconium, the meta-aluminic acid Sodium solution is dissolved in excess sodium hydroxide solution for aluminum sulfate solid and is made.

5. the wet process according to one of claim 2-4 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, It is characterized in that, in step 3, the short grained median for mixing zirconium nickel cobalt binary presoma is 3.5-5.5 μm, the step In rapid four, the shape of ternary precursor is spherical shape or spherical, and wherein position particle size is 10.5-11.5 μm.

6. the wet process according to one of claim 2-5 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, It is characterized in that, the reaction kettle is the reaction kettle equipped with temperature controlled water bath collet, agitating paddle and secondary filter pipe, and reaction kettle bottom liquid is Ammonia density is 0.15-0.25mol/L, and the solution of pH=11.5-12.0 does not cross reaction kettle agitating paddle；Reaction kettle liquid level is close to overflow After head piece, mother liquor is discharged outside reaction kettle by secondary filter pipe, controls solid content 450-650g/L in reaction system.

7. the wet process according to one of claim 2-6 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, It is characterized in that, in step 2, nitrogen is passed through into the reaction kettle of sealing, nitrogen intake is the 1/200~1/ of reactor volume 100, stirring is opened, the pH value of bottom liquid is adjusted to 12.5-13.0 by the sodium hydrate aqueous solution described in 8-10mol/L；Speed of agitator It is adjusted to 400-500r/min, the use of precision metering pump control salting liquid flow is 80-120L/h, control temperature of reaction kettle is 50-65 DEG C, feed time is 3-5 hours, when pH value drops to 11.8-12.5, mixes the generation of zirconium nickel cobalt hydroxide nucleus.

8. the wet process according to one of claim 2-7 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, It is characterized in that, in step 3, it is 80-120L/h that precision metering pump, which controls salting liquid flow, and control ammonia concn is 0.25- 0.35mol/L, and the sodium hydrate aqueous solution flow is adjusted, pH value=11.8-12.5 of reaction solution is controlled, control is anti- Answering temperature is 55-65 DEG C.

9. the wet process according to one of claim 2-8 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, It is characterized in that, in step 4, reaction kettle speed of agitator is adjusted to 500-700r/min, precision metering pump keeps nickel cobalt zirconium metal The flow of mixed salt solution is constant, is at the uniform velocity incremented by sodium aluminate solution flow velocity, adjusts sodium hydrate aqueous solution flow, control reaction PH=11.1-11.4 of solution, control reaction temperature are 55-65 DEG C.

10. the wet process according to one of claim 2-9 mixes the preparation method of zirconium concentration gradient nickel cobalt aluminium ternary precursor, It is characterized in that, in step 5, the pure water temperature of washing is 55-80 DEG C, until stopping washing when Na+≤0.0150% in material It washs, drying temperature is 100-130 DEG C, and screening uses 200 mesh screens.