Nickel-cobalt-manganese hydroxide precursor of fine whisker and preparation method of nickel-cobalt-manganese hydroxide precursor

Abstract

The invention discloses a fine whisker nickel-cobalt-manganese hydroxide precursor and a preparation method thereof, the product morphology can be regulated and controlled by regulating and controlling the temperature and the pH value of the particle size in the growth reaction stage on the premise of not introducing compressed air, the precursor product with fine whisker morphology and large specific surface is prepared, and the repeatability and controllability are good. And meanwhile, the lithium ion battery prepared from the precursor has excellent chemical properties, the first discharge capacity at 0.2 C is up to 207.4 mAh / g, and the first efficiency is up to 89.2%.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium batteries, and in particular relates to a nickel-cobalt-manganese hydroxide precursor of fine whiskers and a preparation method thereof. Background Art

[0002] As a new type of green energy, lithium-ion batteries have the advantages of high specific energy and long cycle life. They are widely used by the battery industry as a new type of green battery. For example, lithium-ion batteries are widely used in the digital field, electric vehicle field, energy storage field, etc. As an important component of lithium-ion batteries, positive electrode materials have a crucial impact on the electrochemical properties of lithium-ion batteries. Nickel-cobalt-manganese ternary positive electrode material is one of the main positive electrode materials for lithium-ion batteries at present, with the characteristics of high specific capacity and good cycle stability.

[0003] The physical and chemical properties of the prepared ternary precursor directly affect the core electrochemical properties of the ternary cathode material. At present, the main method for preparing the ternary precursor (nickel cobalt manganese hydroxide) is the coprecipitation method, that is, the nickel cobalt manganese metal salt solution reacts with the complexing agent and the precipitant under certain conditions to produce spherical secondary particles. After aging, washing, drying and screening, the nickel cobalt manganese hydroxide precursor is finally obtained. The size and morphology of the precursor have a direct impact on the performance of the ternary cathode material of lithium-ion batteries; therefore, synthesizing a nickel cobalt manganese hydroxide precursor with suitable morphology and particle size has become a key factor affecting the performance of lithium nickel cobalt manganese oxide. Chinese patent CN101202343 discloses lithium-ion battery positive electrode material nickel cobalt manganese lithium oxide and its preparation method. The preparation method of the precursor involved in the invention is: using soluble salts of nickel, cobalt and manganese as raw materials, ammonia water or ammonium salt as complexing agent, sodium hydroxide as precipitant, adding water-soluble dispersant, adding water-soluble antioxidant or controlling and protecting with inert gas, adding the solution to the reactor in a parallel flow manner for reaction, alkaline treatment, aging, solid-liquid separation, washing and drying to obtain nickel cobalt manganese hydroxide precursor. The nickel cobalt manganese hydroxide precursor prepared by the above method is a spherical structure with a small specific surface area, and the contact area with the electrolyte during application is also small, and the charge and discharge performance of the battery needs to be improved.

[0004] At present, the industry's method for regulating the fine whisker morphology of nickel-cobalt-manganese hydroxide precursor is mainly to introduce compressed air into the reaction system. The amount of air introduced is closely related to the solid content and particle size growth rate during the reaction process, which will lead to frequent adjustments in the air flow rate, cumbersome processes, and poor reproducibility and batch stability. In addition, the process of controlling the whisker morphology by introducing air will lead to uneven thickness distribution of primary particles, easy to produce fine whiskers, and easy to produce cracked balls.

[0005] Therefore, it is necessary to control the morphology of the nickel-cobalt-manganese ternary precursor to improve the electrochemical performance of the positive electrode material. Summary of the invention

[0006] The first object of the present invention is to provide a nickel-cobalt-manganese hydroxide precursor of fine whiskers and a preparation method thereof.

[0007] The second object of the present invention is to provide a method for preparing a positive electrode material for a lithium ion battery.

[0008] The third object of the present invention is to provide a method for preparing a lithium-ion button battery.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention comprises the following steps: A method for preparing a nickel-cobalt-manganese hydroxide precursor of fine whiskers, the specific preparation steps are: S1: Dissolve soluble salts of nickel, cobalt and manganese in pure water at a molar ratio of 83:11:6 to prepare a metal mixed salt solution of a certain concentration; and simultaneously prepare sodium hydroxide solution and ammonia water of a certain molar concentration; S2: adding pure water into the reaction kettle, starting stirring, and then sequentially adding the ammonia water and sodium hydroxide solution prepared in step S1 as the reaction start-up base liquid; S3: Under an inert atmosphere, the stirring speed is controlled to be 50-600 rpm, and the temperature of the reactor is controlled to be 30-80°C; S4: pumping the nickel-cobalt-manganese metal mixed salt solution, sodium hydroxide solution and ammonia solution described in S1 into the bottom liquid of the synthesis equipment, and controlling the temperature, pH value and ammonia value during the reaction; S5: When the D50 of the reaction slurry reaches the target value, the reaction slurry is filtered, washed, and dried to obtain a precursor material with a fine whisker morphology; S6: Dry the washed precursor material, and after the moisture content is qualified, sieve and demagnetize the precursor material in sequence to obtain a nickel-cobalt-manganese hydroxide precursor material product with a fine whisker morphology.

[0010] Furthermore, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x CO y Mn (1-x-y) (OH)2.

[0011] Furthermore, the particle size D50 of the secondary particles of the nickel-cobalt-manganese hydroxide precursor is 2-12 μm, and the tap density is ≥1.40 g / cm 3 , with a specific surface area of ​​3~25m 2 / g.

[0012] Furthermore, in step S1, the molar concentration of the metal mixed salt solution is 1.0-2.3 mol / L, the molar concentration of the sodium hydroxide solution is 1.0-12.0 mol / L, and the molar concentration of the ammonia water is 1.0-12.0 mol / L.

[0013] Furthermore, in step S2, the pH value of the startup base liquid is 10.0-13.0, and the ammonia concentration is 1.0 g / L-14.0 g / L.

[0014] Furthermore, the synthesis equipment in step S4 is divided into a reactor and a thickener. When the reactor is full, the thickener is fed with materials. The slurry in the thickener is kept circulating with the reactor through a circulating pump. When the thickener is full, the concentration is started, and the clear liquid is discharged. The concentrated slurry continues to react in the reactor and the thickener.

[0015] Furthermore, in step S4, the stirring speed is adjusted according to the growth of D50, specifically: the speed is 340 rpm when the kettle is started, when the particle size is 2.5 μm, the speed is adjusted to 330 rpm, when the particle size is 3.0 μm, the speed is adjusted to 310 rpm, and when the particle size is 3.5 μm, the speed is adjusted to 290 rpm.

[0016] Furthermore, the washing step in step S5 is to first wash with a prepared dilute alkali solution and then wash with pure water; the concentration of the dilute alkali solution is 0.1~2.0 mol / L, and the temperature is 50~70°C; the temperature of the pure water is 50~70°C, and the drying temperature is 80~130°C.

[0017] The present invention also provides a positive electrode material for a lithium-ion battery, which is prepared by using the cobalt-manganese ternary precursor with a fine whisker morphology prepared by the preparation method described above or the cobalt-manganese ternary precursor with a whisker morphology described above and a lithium salt, and the specific steps are: (1) Mixing with lithium: The nickel-cobalt-manganese ternary precursor with fine whisker morphology prepared above and the lithium source powder are mixed uniformly in a high-speed mixer at a stoichiometric molar ratio of 1:1.05-1.12 to obtain a mixed powder; (2) Calcination: After the mixed powder is demagnetized, bowled, cut into pieces, and stacked, it is sent to a roller kiln for sintering and cooling. After unloading, coarse crushing, pulverizing, screening, and demagnetization, the nickel-cobalt-manganese ternary positive electrode material with the fine whisker morphology is obtained.

[0018] The present invention also provides a lithium ion button battery, using the lithium ion battery positive electrode material prepared as described above as the lithium ion battery positive electrode, and the specific steps are: The positive electrode material, conductive carbon and polyvinylidene fluoride (PVDF) were added to N-methyl-2-pyrrolidone (NMP) in a mass ratio of 92.5:5:2.5, mixed evenly to form a positive electrode slurry, and coated on the positive electrode collector and vacuum dried to form a positive electrode. The lithium sheet was used as the negative electrode and assembled into a 2025 button battery in a glove box.

[0019] The beneficial effects of the present invention are: (1) The present invention can control the product morphology by adjusting the temperature and the pH value of the particle size during the growth reaction stage without introducing compressed air, thereby preparing a precursor product with fine whisker morphology and large specific surface area, and has good repeatability and controllability.

[0020] (2) This fine whisker morphology is conducive to the transmission of lithium ions. Sintered lithium ions will diffuse into the interior of the particles as much as possible, reducing particle agglomeration and adhesion at high temperatures and residual alkali. At the same time, the single crystal ternary material obtained by this method has a low degree of cation mixing and a large single particle diameter, which makes the material have a higher first-cycle coulomb efficiency. As a result, the positive electrode material can better maintain its capacitance when it is working under high voltage conditions, thereby improving the high-voltage performance of the ternary positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the nickel-cobalt-manganese hydroxide precursor prepared in Example 1 of the present invention.

[0022] Figure 2 This is a SEM image of the nickel-cobalt-manganese hydroxide precursor prepared in Example 2 of the present invention.

[0023] Figure 3 This is a SEM image of the nickel-cobalt-manganese hydroxide precursor prepared in Example 3 of the present invention.

[0024] Figure 4 This is a SEM image of the nickel-cobalt-manganese hydroxide precursor prepared in Comparative Example 1 of the present invention.

[0025] Figure 5 This is a discharge curve diagram of a lithium-ion button cell prepared from the ternary precursor obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the embodiments.

[0027] Example 1 1. Prepare a 2 mol / L metal salt mixed solution of NiSO4, CoSO4 and MnSO4 in a molar ratio of 83:11:6, and prepare a sodium hydroxide solution with a concentration of 10.5 mol / L and an ammonia solution with a concentration of 7.5 mol / L.

[0028] 2. First add pure water to the stirring area on the upper layer of the reactor, and then add the above-prepared ammonia water and sodium hydroxide solution into the reactor in turn to form a startup base liquid with an ammonia concentration of 3.50g / L and a pH of 12.20.

[0029] 3. Introduce nitrogen into the reactor, start stirring, control the speed of the reactor to 340 rpm, and raise the temperature of the reactor to 38°C and stabilize it.

[0030] 4. Use a metering pump to add the prepared nickel, cobalt, manganese metal mixed salt solution, ammonia water and sodium hydroxide solution into the reactor in sequence, and start the feeding reaction under the protection of nitrogen gas. During the reaction granulation, the temperature is controlled at 38°C, the ammonia value is 3.50g / L, and the reaction is carried out at a pH value of 12.20 for 10 minutes. After 10 minutes, the pH is slowly reduced to 10.70, and the other conditions remain unchanged.

[0031] 5. After the reactor liquid level reaches full, the slurry in the reactor begins to be pumped into the thickener, and the slurry keeps circulating between the reactor and the thickener. After the thickener reaches full level, the concentration is turned on, the clear liquid is discharged, and the concentrated slurry continues to react in the system. When D50 reaches 4μm, stop feeding into the reactor, and then discharge the slurry from the reactor and the thickener into the aging tank.

[0032] 6. After solid-liquid separation, the slurry in the aging tank is washed with 0.8 mol / L alkali solution at a temperature of 60°C and pure water at a temperature of 60°C in turn to obtain a precursor material with a fine whisker morphology.

[0033] 7. After drying the washed precursor material at 80° C. for 4 hours, the temperature is raised to 120° C., and after the moisture content is qualified, the precursor material is sieved and demagnetized in sequence to obtain a nickel-cobalt-manganese hydroxide precursor material product with a fine whisker morphology.

[0034] Example 2 1. Prepare a 2 mol / L metal salt mixed solution of NiSO4, CoSO4 and MnSO4 in a molar ratio of 83:11:6, and prepare a sodium hydroxide solution with a concentration of 10.5 mol / L and an ammonia solution with a concentration of 7.5 mol / L.

[0035] 2. First add pure water to the stirring area on the upper layer of the reactor, and then add the above-prepared ammonia water and sodium hydroxide solution into the reactor in turn to form a startup base liquid with an ammonia concentration of 3.50g / L and a pH of 12.20.

[0036] 3. Introduce nitrogen into the reactor, start stirring, control the speed of the reactor to 340 rpm, and raise the temperature of the reactor to 55°C and stabilize it.

[0037] 4. Use a metering pump to add the prepared nickel, cobalt, manganese metal mixed salt solution, ammonia water and sodium hydroxide solution into the reactor in sequence, and start the feeding reaction under the protection of nitrogen gas. During the reaction granulation, the temperature is controlled at 55°C, the ammonia value is 3.50g / L, and the reaction is carried out at a pH value of 12.20 for 10 minutes. After 10 minutes, the pH is slowly reduced to 10.70, and the other conditions remain unchanged.

[0038] 5. After the reactor liquid level reaches full, the slurry in the reactor begins to be pumped into the thickener. The slurry keeps circulating between the reactor and the thickener. After the thickener reaches full level, the concentration is started and the clear liquid is discharged. The concentrated slurry continues to react in the system. When D50 reaches 4μm, the feeding to the reactor is stopped, and then the slurry in the reactor and the thickener is discharged into the aging tank.

[0039] 6. After solid-liquid separation, the slurry in the aging tank is washed with 0.8 mol / L alkali solution at a temperature of 60°C and pure water at a temperature of 60°C in turn to obtain a precursor material with a fine whisker morphology.

[0040] 7. After drying the washed precursor material at 80°C for 4 hours, the temperature is raised to 120°C. After the moisture content is qualified, the precursor material is sieved and demagnetized to obtain a nickel-cobalt-manganese hydroxide precursor material product.

[0041] Example 3 1. Prepare a 2 mol / L metal salt mixed solution of NiSO4, CoSO4 and MnSO4 in a molar ratio of 83:11:6, and prepare a sodium hydroxide solution with a concentration of 10.5 mol / L and an ammonia solution with a concentration of 7.5 mol / L.

[0042] 2. First add pure water to the stirring area on the upper layer of the reactor, and then add the above-prepared ammonia water and sodium hydroxide solution into the reactor in turn to form a startup base liquid with an ammonia concentration of 3.50g / L and a pH of 12.20.

[0043] 3. Introduce nitrogen into the reactor, start stirring, control the speed of the reactor to 340 rpm, and raise the temperature of the reactor to 38°C and stabilize it.

[0044] 4. Use a metering pump to add the prepared nickel, cobalt, manganese metal mixed salt solution, ammonia water and sodium hydroxide solution into the reactor in sequence, and start the feeding reaction under the protection of nitrogen gas. During the reaction granulation, the temperature is controlled at 38°C, the ammonia value is 3.50g / L, and the reaction is carried out at a pH value of 12.20 for 10 minutes. After 10 minutes, the pH is slowly reduced to 12.10, and the other conditions remain unchanged.

[0045] 5. After the reactor liquid level reaches full, the slurry in the reactor begins to be pumped into the thickener, and the slurry keeps circulating between the reactor and the thickener. When the thickener reaches full level, the concentration is turned on, the clear liquid is discharged, and the concentrated slurry continues to react in the system. When D50 reaches 4μm, the feed to the reactor is stopped, and the slurry in the reactor and the thickener is discharged into the aging tank.

[0046] 6. After solid-liquid separation, the slurry in the aging tank is washed with 0.8 mol / L alkali solution at a temperature of 60°C and pure water at a temperature of 60°C in turn to obtain a washed filter cake.

[0047] 7. After drying the washed filter cake at 80°C for 4 hours, the temperature is raised to 120°C. After the moisture content is qualified, the filter cake is sieved and demagnetized to obtain the nickel-cobalt-manganese hydroxide precursor material product.

[0048] Comparative Example 1 1. Prepare a 2 mol / L metal salt mixed solution of NiSO4, CoSO4 and MnSO4 in a molar ratio of 83:11:6, and prepare a sodium hydroxide solution with a concentration of 10.5 mol / L and an ammonia solution with a concentration of 7.5 mol / L.

[0049] 2. First add pure water to the stirring area on the upper layer of the reactor, and then add the above-prepared ammonia water and sodium hydroxide solution into the reactor in turn to form a startup base liquid with an ammonia concentration of 3.50g / L and a pH of 12.20.

[0050] 3. Introduce nitrogen into the reactor, start stirring, control the speed of the reactor to 340 rpm, and raise the temperature of the reactor to 55°C and stabilize it.

[0051] 4. Use a metering pump to add the prepared nickel, cobalt, manganese metal mixed salt solution, ammonia water and sodium hydroxide solution into the reactor in sequence, and start the feeding reaction under the protection of nitrogen gas. During the reaction granulation, the temperature is controlled at 55°C, the ammonia value is 3.50g / L, and the reaction is carried out at a pH value of 12.20 for 10 minutes. After 10 minutes, the pH is slowly reduced to 10.70, and the other conditions remain unchanged.

[0052] 5. After the reactor liquid level reaches full, the slurry in the reactor begins to be pumped into the thickener, and the slurry keeps circulating between the reactor and the thickener. After the thickener reaches full reactor liquid level, the concentration is started, and the clear liquid is discharged. The concentrated slurry continues to react in the system. When D50 reaches 2.0μm, compressed air is introduced into the reactor at an oxygen content of 2%. When D50 reaches 2.5μm, compressed air is introduced into the reactor at an oxygen content of 4%. When D50 reaches 3.0μm, compressed air is introduced into the reactor at an oxygen content of 6%. When D50 reaches 3.5μm, compressed air is introduced into the reactor at an oxygen content of 10%. When D50 reaches 4μm, stop feeding into the reactor, and then discharge the slurry in the reactor and the thickener into the aging tank.

[0053] 6. After solid-liquid separation, the slurry in the aging tank is washed with 0.8 mol / L alkali solution at a temperature of 60°C and pure water at a temperature of 60°C in turn to obtain a washed filter cake.

[0054] 7. After drying the washed filter cake at 80°C for 4 hours, the temperature is raised to 120°C. After the moisture content is qualified, the filter cake is sieved and demagnetized to obtain the nickel-cobalt-manganese hydroxide precursor material product.

[0055] Experiment 1: Using an electron scanning microscope to observe and detect the nickel-cobalt-manganese hydroxide precursor materials prepared in Examples 1 to 3 and Comparative Example 1, the particle size and specific surface area data are shown in Table 1, and the SEM images are shown in Figures 1 to 4 .

[0056] Table 1 Particle size and specific surface area data of products of Examples 1 to 3 and Comparative Example 1 From Table 1 and Figures 1 to 4 It can be seen that the nickel-cobalt-manganese hydroxide precursor material prepared in Example 1 has the largest specific surface area and the material particle size is more uniform.

[0057] Experiment 2: The nickel cobalt manganese hydroxide precursor materials prepared in Examples 1 to 3 and Comparative Example 1 were used to prepare lithium-ion battery positive electrode materials, and then these lithium-ion battery positive electrode materials were used as lithium-ion battery positive electrodes to prepare lithium-ion button batteries. Finally, these lithium-ion button batteries were subjected to electrochemical performance tests under conditions of 2.75 to 4.35 V. The results are shown in Table 2.

[0058] Table 2 Electrochemical performance data of each embodiment and comparative example 1 It can be seen from Table 2 that the positive electrode material prepared from the ternary precursor obtained in Example 1 performs best in lithium ion, with an initial discharge capacity of up to 207.4 mAh / g at 0.2C and an initial efficiency of up to 89.2%.

Claims

1. A method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor, characterized in that: The chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x CO y Mn (1-x-y) (OH)2, where 0.4 < x < 0.95, 0.02 < y < 0.

3. The specific preparation steps are as follows: S1: Dissolve soluble salts of nickel, cobalt and manganese in pure water at a molar ratio of 83:11:6 to prepare a metal mixed salt solution of a certain concentration; and simultaneously prepare sodium hydroxide solution and ammonia water of a certain molar concentration; S2: Add pure water into the reactor, start stirring, and then add the ammonia water and sodium hydroxide solution prepared in S1 in sequence as the reaction start-up base liquid; S3: Under an inert atmosphere, the stirring speed is controlled to be 50-600 rpm, and the temperature of the reactor is controlled to be 30-80°C; S4: pumping the nickel-cobalt-manganese metal mixed salt solution, sodium hydroxide solution and ammonia solution described in S1 into the bottom liquid of the synthesis equipment, starting the feeding reaction under the protection of nitrogen gas, controlling the temperature at 36-40°C during the reaction granulation, and the ammonia value at 3.45-3.55 g / L, reacting for 10 minutes at a pH value of 12.20, and then slowly reducing the pH to 10.65-10.75 after 10 minutes, and keeping the other conditions unchanged; S5: When the D50 of the reaction slurry reaches the target value, the reaction slurry is filtered, washed, and dried to obtain a precursor material with a fine whisker morphology; S6: Dry the washed precursor material, and after the moisture content is qualified, sieve and demagnetize the precursor material in sequence to obtain a nickel-cobalt-manganese hydroxide precursor material product with a fine whisker morphology.

2. The method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor according to claim 1, characterized in that: The particle size D50 of the secondary particles of the nickel-cobalt-manganese hydroxide precursor is 2~12μm; the tap density is ≥1.40g / cm 3 , with a specific surface area of ​​3~25m 2 / g.

3. The method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor according to claim 1, characterized in that: The molar concentration of the metal mixed salt solution in S1 is 1.0-2.3 mol / L, the molar concentration of the sodium hydroxide solution is 1.0-12.0 mol / L, and the molar concentration of the ammonia water is 1.0-12.0 mol / L.

4. The method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor according to claim 1, characterized in that: The pH value of the startup base liquid described in S2 is 10.0~13.0, and the ammonia concentration is 1.0g / L~14.0g / L.

5. The method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor according to claim 1, characterized in that: The synthesis equipment described in S4 is divided into a reactor and a thickener. When the reactor is full, the thickener is fed with materials. The slurry in the thickener is kept circulating with the reactor through a circulation pump. When the thickener is full, the concentration is started and the clear liquid is discharged. The concentrated slurry continues to react in the reactor and the thickener.

6. The method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor according to claim 1, characterized in that: The stirring speed in S4 is adjusted according to the growth of D50, specifically: the speed is 340 rpm when the kettle is started, when the particle size is 2.5 μm, the speed is adjusted to 330 rpm, when the particle size is 3.0 μm, the speed is adjusted to 310 rpm, and when the particle size is 3.5 μm, the speed is adjusted to 290 rpm.

7. The method for preparing a fine whisker nickel-cobalt-manganese hydroxide precursor according to claim 1, characterized in that: The washing step in S5 is to first wash with a prepared dilute alkali solution and then wash with pure water; the concentration of the dilute alkali solution is 0.1-2.0 mol / L, and the temperature is 50-70°C; the temperature of the pure water is 50-70°C, and the drying temperature is 80-130°C.

8. A positive electrode material for a lithium ion battery, characterized in that: The fine whisker is prepared by using a nickel-cobalt-manganese ternary precursor and a lithium salt prepared by the preparation method according to any one of claims 1 to 7, and the specific preparation steps are: (1) Mixing with lithium: The nickel-cobalt-manganese ternary precursor with fine whisker morphology prepared above and the lithium source powder are weighed in a molar ratio of 1:1.05-1.12, and mixed evenly in a high-speed mixer to obtain a mixed powder; (2) Calcination: After the mixed powder is demagnetized, bowled, cut into pieces, and stacked, it is sent to a roller kiln for sintering and cooling. After unloading, coarse crushing, pulverizing, screening, and demagnetization, the nickel-cobalt-manganese ternary positive electrode material with the fine whisker morphology is obtained.

9. A lithium ion battery, comprising a positive electrode prepared from the lithium ion battery positive electrode material according to claim 8.

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