A method for preparing large-particle cobalt tetroxide

Abstract

The present invention belongs to the technical field of battery material preparation, and particularly relates to a method for preparing large-particle cobalt trioxide, comprising the following steps: mixing a cobalt salt solution with a precipitant solution A containing carbonate, separating solid and liquid after reaction, taking a solid phase for drying and crushing to obtain amorphous nano cobalt carbonate; mixing a cobalt salt solution with a precipitant solution B containing carbonate and a precipitant solution C containing carbonate, reacting to generate cobalt carbonate particles, adding amorphous nano cobalt carbonate, reacting to obtain a reaction solution containing a cobalt carbonate matrix coated with amorphous nano cobalt carbonate; adding a precipitant solution D containing hydroxide to the reaction solution, and then adding a cobalt salt solution and the precipitant solution D, reacting to generate mixed particles, separating solid and liquid, taking a solid phase to obtain a cobalt carbonate / cobalt hydroxide mixture, sintering once, mixing with amorphous nano cobalt carbonate, and sintering twice to obtain large-particle cobalt trioxide.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material preparation, and in particular relates to a method for preparing large-particle cobalt tetroxide. Background Art

[0002] Lithium cobalt oxide positive electrode materials have the advantage of high energy density and are mainly used in the 3C field. Cobalt tetroxide, as a precursor of lithium cobalt oxide positive electrode materials, has been widely studied because of its stable structure, high theoretical capacity, and good electrochemical properties.

[0003] The currently disclosed method for preparing large-particle cobalt oxide precursors is generally to synthesize large-particle cobalt hydroxide or cobalt carbonate by wet method, and then calcine at high temperature. However, in the actual preparation process, due to the loose structure of cobalt hydroxide, the sintered large-particle cobalt oxide usually has a low tap density. Although cobalt carbonate has a compact structure, it releases carbon dioxide during high-temperature calcination, which easily causes cracking and damage of particles, affecting the performance of the final cobalt oxide.

[0004] Therefore, it is urgent to develop a new method for preparing large-particle cobalt tetroxide. Summary of the invention

[0005] The present disclosure aims to solve at least one of the technical problems existing in the related art. To this end, the present disclosure provides a method for preparing large particles of cobalt tetroxide, which can avoid particle breakage during the preparation process and obtain large particles of cobalt tetroxide with high tap density.

[0006] The above technical objectives of the present disclosure are achieved through the following technical solutions:

[0007] A method for preparing large-particle cobalt trioxide comprises the following steps:

[0008] (1) mixing a cobalt salt solution with a precipitant solution A containing carbonate, separating the solid and the liquid after the reaction, drying and crushing the solid phase to obtain amorphous nano-cobalt carbonate;

[0009] (2) mixing the cobalt salt solution with the precipitant solution B containing carbonate and the precipitant solution C containing carbonate to react and generate cobalt carbonate particles, and then adding the amorphous nano-cobalt carbonate prepared in step (1) to react and obtain a reaction solution containing a cobalt carbonate matrix coated with the amorphous nano-cobalt carbonate;

[0010] (3) under an inert atmosphere, adding a precipitant solution D containing hydroxide to the reaction solution of step (2) to adjust the pH to neutral or alkaline, then adding a cobalt salt solution and a precipitant solution D containing hydroxide, reacting to generate mixed particles, separating the solid and the liquid, taking the solid phase to obtain a cobalt carbonate / cobalt hydroxide mixture, and sintering once to obtain a large particle cobalt oxide semi-finished product;

[0011] (4) mixing the large-particle cobalt oxide semi-finished product obtained in step (3) with the amorphous nano-cobalt carbonate obtained in step (1), and performing secondary sintering to obtain large-particle cobalt oxide.

[0012] In one embodiment, the cobalt salt solution is at least one of cobalt chloride, cobalt nitrate and cobalt sulfate.

[0013] In one embodiment, the concentration of cobalt ions in the cobalt salt solution is 1.5-2.0 mol / L.

[0014] In one embodiment, the precipitant solution A is at least one of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, and the concentration of the precipitant solution A is 250-300 g / L.

[0015] In one embodiment, the precipitant solution B is at least one of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, and the concentration of the precipitant solution B is 60-120 g / L.

[0016] In one embodiment, the precipitant solution C is at least one of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, and the concentration of the precipitant solution C is 160-240 g.

[0017] In one embodiment, the precipitant solution D is at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the precipitant solution D is 320-480 g / L.

[0018] In one embodiment, in step (1), the cobalt salt solution is mixed with the precipitant solution A containing carbonate ions by using the precipitant solution A as the base solution and then adding the cobalt salt solution.

[0019] In one embodiment, in step (1), the cobalt salt solution is added gradually under stirring.

[0020] In one embodiment, in step (1), the stirring speed is 40-50 Hz.

[0021] In one embodiment, in step (1), the reaction temperature is 25-30°C.

[0022] In one embodiment, in step (1), the pH of the reaction is 8.0-8.5.

[0023] In one embodiment, in step (1), the dry crushing is performed using a disc-shaped grinding device.

[0024] In one embodiment, in step (1), the D50 of the amorphous nano-cobalt carbonate is less than 1 μm.

[0025] In one embodiment, in step (2), the cobalt salt solution is mixed with the precipitant solution B containing carbonate and the precipitant solution C containing carbonate, with the precipitant solution B as the base solution, and then the cobalt salt solution and the precipitant solution C containing carbonate are added.

[0026] In one embodiment, in step (2), the adding of the cobalt salt solution and the precipitant solution C containing carbonate refers to first adding the cobalt salt solution and the precipitant solution C in parallel at 38-45° C., then keeping the flow rate of the cobalt salt solution unchanged, adjusting the flow rate of the precipitant solution C to control the synthesized pH to 7-8, and controlling the stirring frequency to 15-20 Hz to generate cobalt carbonate particles with a D50 of 15-16 μm.

[0027] In one embodiment, in step (2), the mass of the amorphous nano-cobalt carbonate added is 1 / 20-1 / 50 of the total mass of the cobalt carbonate particles and the amorphous nano-cobalt carbonate.

[0028] In one embodiment, in step (3), after adding the precipitant solution D containing hydroxide to the reaction solution of step (2), the reaction temperature is controlled to be 60-70° C. and the stirring frequency is 10-15 Hz.

[0029] In one embodiment, in step (3), the pH is adjusted to 9-10.

[0030] In one embodiment, in step (3), adding the cobalt salt solution and the precipitant solution D means first adding the cobalt salt solution and the precipitant solution D in parallel, then keeping the flow rate of the cobalt salt solution unchanged, and adjusting the flow rate of the precipitant solution D to control the synthesized pH to 9-10 to generate mixed particles with a D50 of 18-20 μm.

[0031] In one embodiment, in step (3), the primary sintering temperature is 350-450° C., and the primary sintering time is 2-4 hours.

[0032] In one embodiment, in step (4), the mass ratio of the large-particle cobalt oxide semi-finished product to the amorphous nano-cobalt carbonate is (10-15):1.

[0033] In one embodiment, in step (4), the secondary sintering temperature is 720-750° C., and the secondary sintering time is 2-4 hours.

[0034] In one embodiment, a method for preparing large particles of cobalt oxide comprises the following steps:

[0035] (1) preparing a solution: preparing a cobalt salt solution, a precipitant solution A containing carbonate, a precipitant solution B and a precipitant solution C, and a precipitant solution D containing hydroxide, wherein the cobalt salt solution is one or more of a cobalt chloride solution, a cobalt nitrate solution and a cobalt sulfate solution, and the cobalt ion concentration in the cobalt salt solution is 1.5-2.0 mol / L; the precipitant solution A, the precipitant solution B and the precipitant solution C are one or more of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, the concentration of the precipitant solution A is 250-300 g / L, the concentration of the precipitant solution B is 60-120 g / L, and the concentration of the precipitant solution C is 160-240 g / L; the precipitant solution D is one or more of sodium hydroxide and potassium hydroxide, and the concentration is 320-480 g / L;

[0036] (2) Preparation of amorphous nano-cobalt carbonate: Add precipitant solution A as a bottom liquid into a reactor, accounting for 50% of the volume of the reactor, control the reaction temperature at 25-30°C, stir at 40-50Hz, pass the cobalt salt solution through a single channel, and control the reaction pH at 8.0-8.5. When the volume of the reactor liquid reaches 80% of the effective volume, stop adding liquid, and drain the obtained slurry into a centrifuge for centrifugal dehydration, wash with pure water 3-5 times, and then dry and crush by a disc nest mill to obtain amorphous nano-cobalt carbonate with D50 <1μm;

[0037] (3) Synthesis of cobalt carbonate matrix: Add precipitant solution B as the bottom liquid in the reaction kettle, accounting for 50% of the volume of the reaction kettle, add a certain amount of cobalt salt solution and precipitant solution C in parallel at 38-45° C., keep the flow rate of the cobalt salt solution unchanged, adjust the flow rate of the precipitant solution C to control the synthesis pH to 7-8, stir at 15-20 Hz, let the kettle stand after it is full, remove the supernatant liquid, continue to feed, and terminate the reaction when D50 reaches 15-16 μm, add the amorphous nano-cobalt carbonate prepared in step (2) into the reaction kettle and stir for 30-60 min, wherein the mass of the added material is 1 / 20-1 / 50 of the mass of the material in the kettle, to obtain a reaction liquid containing a cobalt carbonate matrix coated with amorphous nano-cobalt carbonate;

[0038] (4) Synthesis of the cobalt hydroxide coating layer: the reactor of step (3) is continuously filled with an inert gas, wherein the inert gas is nitrogen or argon, and then a certain amount of precipitant solution D is pumped into the reaction solution of step (3), the pH value of the bottom solution is adjusted to 9.0-10.0, the temperature is 60-70° C., and the stirring frequency is 10-15 Hz, and then the cobalt salt solution and the precipitant solution D are added in parallel, the flow rate of the cobalt salt solution is kept constant, the flow rate of the precipitant solution D is adjusted, the pH of the synthesis is controlled to be 9-10, and the inert gas is continuously introduced until the D50 reaches 18-20 μm, the reaction is terminated, the material is filtered in a centrifuge to dry the mother liquor, and the material is washed with pure water for 3-5 times to obtain a cobalt carbonate / cobalt hydroxide mixture;

[0039] (5) primary sintering: calcining the cobalt carbonate / cobalt hydroxide mixture obtained in step (4) at 350-450° C. for 2-4 h in a box furnace to obtain a large-particle cobalt oxide semi-finished product;

[0040] (6) Coating amorphous cobalt carbonate: The large-particle cobalt oxide semi-finished product obtained in the above step (5) and the amorphous cobalt carbonate obtained in the step (2) are mixed in a spiral mixer at a mass ratio of (10-15):1 for 30-60 minutes to obtain a sample of cobalt oxide coated amorphous cobalt carbonate;

[0041] (7) Secondary sintering: The sample obtained in step (6) is calcined in a box furnace at 720-750° C. for 2-4 h to obtain a large-particle cobalt trioxide product.

[0042] The beneficial effects of the present disclosure are:

[0043] (1) Cobalt hydroxide is synthesized into an intercalated stacking growth mode of hexagonal wafers, which is usually loose and has a low tap density. After being sintered into cobalt tetroxide, it will also inherit its loose structure, which ultimately affects the volume energy density of the positive electrode material; cobalt carbonate is synthesized into a granular primary particle stacking growth mode, which is usually compact and has a high tap density. However, during the sintering process into cobalt tetroxide, if the carbon dioxide gas cannot be released in time, it will cause the internal stress of the particles to increase, resulting in the cracking and crushing of the spherical particles, affecting the material processing performance. The present disclosure synthesizes a large-particle mixed material with a core of cobalt carbonate and an outer shell of cobalt hydroxide, thereby ensuring the compactness of the core and making it have a high tap density; at the same time, the flaky structure on the surface of the particles can provide a wider channel for the release of carbon dioxide gas generated during the thermal decomposition of the core cobalt carbonate, reduce the internal stress of the particles, and completely release the gas under the condition of low-temperature sintering, avoiding particle damage. In view of the relatively loose surface structure, the present invention first synthesizes amorphous cobalt carbonate, and grinds and dries it through a disc nest mill to make it more dispersible. The amorphous cobalt carbonate is fully mixed with the semi-finished cobalt oxide after primary sintering in a certain proportion to fill the gaps on the surface. Then, through high-temperature sintering, the amorphous cobalt carbonate coated on the surface is fully decomposed and fused with the matrix cobalt oxide, thereby improving the overall crystallinity of the particles. Finally, large particles of cobalt oxide with a complete surface, a dense inner core and an outer layer are prepared, which have a high tap density.

[0044] (2) The present disclosure adopts a positive addition method in the process of synthesizing amorphous cobalt carbonate: adding a cobalt salt solution alone to a solution containing a carbonate precipitant solution as a base solution can increase the supersaturation at the moment of feeding, which is beneficial to the formation of amorphous cobalt carbonate.

[0045] (3) In order to make cobalt hydroxide uniformly coated on the cobalt carbonate matrix, the present invention utilizes the characteristics of amorphous nano-cobalt carbonate with high specific surface area, adsorption capacity and surface energy, and first coats it on the cobalt carbonate matrix, which not only improves the density of the cobalt carbonate matrix, fills surface defects, and further improves the tap density of the finished product, but also enables the cobalt carbonate matrix to have strong adsorption capacity and surface energy, which helps the cobalt hydroxide primary particles to be uniformly adsorbed and grown on the surface of the cobalt carbonate matrix in the early stage of synthesizing cobalt hydroxide, rather than cobalt hydroxide nucleating alone in the system, so that the product has better consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a SEM image of the amorphous cobalt carbonate obtained in step (2) of Example 1 of the present disclosure;

[0047] Figure 2 This is a SEM image of the semi-finished product of large-particle cobalt oxide obtained in step (5) of Example 1 of the present disclosure;

[0048] Figure 3 This is a SEM image of the finished product of large-particle cobalt tetroxide obtained in Example 1 of the present disclosure;

[0049] Figure 4 This is the XRD diagram of the finished product of large-particle cobalt tetroxide obtained in Example 1 of the present disclosure;

[0050] Figure 5 This is a SEM image of the finished product of large-particle cobalt tetroxide obtained in Comparative Example 1 of the present disclosure;

[0051] Figure 6 This is a SEM image of the coated cobalt hydroxide obtained in Comparative Example 2 of the present disclosure. DETAILED DESCRIPTION

[0052] The present disclosure is further described below in conjunction with specific embodiments.

[0053] Embodiment 1:

[0054] A method for preparing large-particle cobalt oxide comprises the following steps:

[0055] (1) preparing a solution: 1.5 mol / L cobalt chloride solution, 250 g / L ammonium bicarbonate solution A, 60 g / L ammonium bicarbonate solution B, 160 g / L ammonium bicarbonate solution C, and 320 g / L sodium hydroxide solution D;

[0056] (2) Preparation of amorphous cobalt carbonate:

[0057] Ammonium bicarbonate solution A was added into the reactor as the bottom liquid, accounting for 50% of the volume of the reactor, the temperature was 25°C, the stirring speed was 50 Hz, and the cobalt chloride solution was introduced separately, and the flow rate of the cobalt chloride solution was adjusted to control the pH to 8.2. When the volume of the reactor liquid reached 80% of the effective volume, the liquid was stopped, and the obtained slurry was discharged into a centrifuge for centrifugal dehydration, washed with pure water 5 times, and dried and crushed by a disc nest mill to obtain amorphous cobalt carbonate with D50=0.82μm. The SEM image of the obtained amorphous cobalt carbonate is as shown below: Figure 1 As shown, from Figure 1 It can be seen that the prepared amorphous cobalt carbonate has good dispersibility;

[0058] (3) Cobalt carbonate matrix synthesis:

[0059] Add ammonium bicarbonate solution B as a bottom liquid in a reaction kettle, accounting for 50% of the volume of the reaction kettle, add 5 L / h of cobalt chloride solution and ammonium bicarbonate solution C in parallel at 38° C., keep the flow rate of the cobalt chloride solution unchanged, adjust the flow rate of the ammonium bicarbonate solution C to control the synthesized pH to 7.0, stir at 20 Hz, let the kettle stand after it is full, remove the supernatant, continue to add materials, and terminate the reaction when D50 reaches 15.2 μm, add the amorphous nano-cobalt carbonate prepared in step (2) into the reaction kettle and stir for 30 minutes, wherein the added mass is 1 / 30 of the mass of the material in the kettle, to obtain a reaction solution containing a cobalt carbonate matrix coated with amorphous nano-cobalt carbonate;

[0060] (4) Synthesis of cobalt hydroxide coating layer:

[0061] The reactor in step (3) is continuously charged with nitrogen, and then a certain amount of sodium hydroxide solution D is pumped into the reaction solution to adjust the pH value of the bottom solution to 9.0, the temperature to 60° C., and the stirring frequency to 15 Hz. Then, the cobalt chloride solution and the sodium hydroxide solution D are flowed in parallel, the flow rate of the cobalt chloride solution is kept at 5 L / h, and the flow rate of the sodium hydroxide solution D is adjusted to control the synthesized pH to 9.0. Nitrogen is continuously introduced during the parallel flow, and the reaction is terminated when the D50 reaches 18.3 μm. The material is filtered in a centrifuge to dry the mother liquor and washed 3 times to obtain a cobalt carbonate / cobalt hydroxide mixture;

[0062] (5) Primary sintering: The cobalt carbonate / cobalt hydroxide mixture obtained in step (4) was calcined in a box furnace at 350° C. for 4 h to obtain a large-particle cobalt oxide semi-finished product. The SEM image of the obtained large-particle cobalt oxide semi-finished product is as follows: Figure 2 As shown, from Figure 2 It can be seen that there are many gaps on the surface of the large-particle cobalt oxide semi-finished product;

[0063] (6) Coating amorphous cobalt carbonate

[0064] The large-particle cobalt oxide semi-finished product obtained in step (5) and the amorphous cobalt carbonate obtained in step (2) are mixed in a spiral mixer at a mass ratio of 10:1 for 30 to 60 minutes to obtain a sample of cobalt oxide coated amorphous cobalt carbonate;

[0065] (7) Secondary sintering: the sample obtained in step (6) is calcined in a box furnace at 750° C. for 4 h to obtain a large-particle cobalt oxide product. The SEM image of the large-particle cobalt oxide product is as follows: Figure 3 As shown, the XRD pattern of the obtained large particle cobalt oxide product is as follows Figure 4 As shown, from Figure 3 It can be seen that the surface of the large cobalt oxide finished particles is dense and smooth. Figure 4 The results show that the large-particle cobalt oxide product is pure cobalt oxide with good crystallinity. The D50 of the large-particle cobalt oxide product is 16.7 μm and the tap density is 2.74 g / cm 3 , where the measurement standard for tap density is: GB / T5162-2006.

[0066] Embodiment 2:

[0067] A method for preparing large-particle cobalt oxide comprises the following steps:

[0068] (1) preparing a solution: 1.8 mol / L cobalt chloride solution, 300 g / L ammonium bicarbonate solution A, 80 g / L ammonium bicarbonate solution B, 200 g / L ammonium bicarbonate solution C, and 400 g / L sodium hydroxide solution D;

[0069] (2) Preparation of amorphous cobalt carbonate:

[0070] Add ammonium bicarbonate solution A as a bottom liquid in a reactor, accounting for 50% of the volume of the reactor, the temperature is 30° C., the stirring speed is 45 Hz, and cobalt chloride solution is introduced separately, and the flow rate of the cobalt chloride solution is adjusted to control the pH value to 8.5. When the volume of the reactor liquid reaches 80% of the effective volume, the liquid is stopped, and the obtained slurry is discharged into a centrifuge for centrifugal dehydration, washed with pure water 5 times, and dried and crushed by a disc nest mill to obtain amorphous cobalt carbonate with D50=0.74 μm;

[0071] (3) Cobalt carbonate matrix synthesis:

[0072] Add ammonium bicarbonate solution B as a bottom liquid in a reaction kettle, accounting for 50% of the volume of the reaction kettle, add 50L / h of cobalt chloride solution and ammonium bicarbonate solution C in parallel at 41°C, keep the flow rate of the cobalt chloride solution unchanged, adjust the flow rate of the ammonium bicarbonate solution C to control the synthesized pH to 7.5, stir at 18Hz, let the kettle stand after it is full, remove the supernatant, continue to feed, and terminate the reaction when D50 reaches 15.7μm, add the amorphous nano cobalt carbonate prepared in step (2) into the reaction kettle and stir for 60min, wherein the input mass is 1 / 20 of the mass of the material in the kettle, to obtain a reaction solution containing a cobalt carbonate matrix coated with amorphous nano cobalt carbonate;

[0073] (4) Synthesis of cobalt hydroxide coating layer:

[0074] The reactor in step (3) is continuously filled with argon gas, and then a certain amount of sodium hydroxide solution D is pumped into the reaction solution to adjust the pH value of the bottom solution to 9.5, the temperature to 65° C., and the stirring frequency to 13 Hz. Then, the cobalt chloride solution and the sodium hydroxide solution D are flowed in parallel, the flow rate of the cobalt chloride solution is kept at 50 L / h, and the flow rate of the sodium hydroxide solution D is adjusted to control the synthesized pH to 9.5. Argon gas is continuously introduced during the parallel flow, and the reaction is terminated when the D50 reaches 19.2 μm. The material is filtered in a centrifuge to dry the mother liquor and washed 5 times to obtain a cobalt carbonate / cobalt hydroxide mixture;

[0075] (5) primary sintering: calcining the cobalt carbonate / cobalt hydroxide mixture obtained in step (4) in a box furnace at 400° C. for 4 h to obtain a large-particle cobalt trioxide semi-finished product;

[0076] (6) Coating amorphous cobalt carbonate

[0077] The large-particle cobalt oxide semi-finished product obtained in step (5) and the amorphous cobalt carbonate obtained in step (2) are mixed in a spiral mixer at a mass ratio of 12:1 for 50 minutes to obtain a sample of cobalt oxide-coated amorphous cobalt carbonate;

[0078] (7) Secondary sintering: the sample obtained in step (6) was calcined in a box furnace at 730° C. for 4 h to obtain a large-particle cobalt oxide product. The obtained large-particle cobalt oxide product has a D50 of 16.7 μm and a tap density of 2.69 g / cm 3 ;

[0079] Comparative Example 1:

[0080] A method for preparing large-particle cobalt trioxide comprises the following steps:

[0081] (1) Prepare solution: 1.5 mol / L cobalt chloride solution, 60 g / L ammonium bicarbonate solution A, and 160 g / L ammonium bicarbonate solution B;

[0082] (2) Cobalt carbonate synthesis:

[0083] Add 60 g / L ammonium bicarbonate solution A as a bottom liquid in a reaction kettle, accounting for 50% of the volume of the reaction kettle, add 5 L / h of cobalt chloride solution and ammonium bicarbonate solution B in parallel at 38° C., keep the flow rate of the cobalt chloride solution unchanged, adjust the flow rate of the ammonium bicarbonate solution B to control the synthesized pH to 7.0, stir at 20 Hz, let the kettle stand after it is full, remove the supernatant, continue to feed, and terminate the reaction when D50 reaches 18.4 μm, and filter the mother liquor in a centrifuge to obtain large-particle cobalt carbonate;

[0084] (3) Calcination

[0085] The large-particle cobalt carbonate obtained in the above step (2) was calcined at 720° C. in a box furnace for 4 h to obtain a large-particle cobalt tetroxide product. The SEM image of the obtained large-particle cobalt tetroxide product is as follows: Figure 5 As shown, Figure 5 The particles showed cracking and powdering. The D50 of the large cobalt oxide particles was 16.4 μm and the tap density was 2.10 g / cm 3 .

[0086] Comparative Example 2: (The only difference from Example 1 is that the amorphous nano-cobalt carbonate is not coated in step (3))

[0087] A method for preparing large-particle cobalt oxide comprises the following steps:

[0088] (1) preparing a solution: 1.5 mol / L cobalt chloride solution, 250 g / L ammonium bicarbonate solution A, 60 g / L ammonium bicarbonate solution B, 160 g / L ammonium bicarbonate solution C, and 320 g / L sodium hydroxide solution D;

[0089] (2) Preparation of amorphous cobalt carbonate:

[0090] Add ammonium bicarbonate solution A as a bottom liquid in a reactor, accounting for 50% of the volume of the reactor, the temperature is 25° C., the stirring speed is 50 Hz, and cobalt chloride solution is introduced separately, and the flow rate of the cobalt chloride solution is adjusted to control the pH value to 8.2. When the volume of the reactor liquid reaches 80% of the effective volume, the liquid is stopped, and the obtained slurry is discharged into a centrifuge for centrifugal dehydration, washed with pure water 5 times, and dried and crushed by a disc nest mill to obtain amorphous cobalt carbonate with D50=0.82 μm;

[0091] (3) Cobalt carbonate matrix synthesis:

[0092] Add ammonium bicarbonate solution B as a bottom liquid in the reaction kettle, accounting for 50% of the volume of the reaction kettle, add 5 L / h of cobalt chloride solution and ammonium bicarbonate solution C in parallel at 38° C., keep the flow rate of the cobalt chloride solution unchanged, adjust the flow rate of the ammonium bicarbonate solution C to control the synthesized pH to 7.0, stir at 20 Hz, let the kettle stand after it is full, remove the supernatant liquid, and continue to add materials, and terminate the reaction when D50 reaches 15.2 μm to obtain a reaction solution containing a cobalt carbonate matrix;

[0093] (4) Synthesis of cobalt hydroxide coating layer:

[0094] The reactor in step (3) is continuously charged with nitrogen, and then a certain amount of sodium hydroxide solution D is pumped into the reaction solution to adjust the pH value of the bottom solution to 9.0, the temperature to 60° C., and the stirring frequency to 15 Hz. Then, the cobalt chloride solution and the sodium hydroxide solution D are flowed in parallel, the flow rate of the cobalt chloride solution is kept at 5 L / h, and the flow rate of the sodium hydroxide solution D is adjusted to control the synthesized pH to 9.0. Nitrogen is continuously introduced during the parallel flow, and the reaction is terminated when the D50 reaches 18.3 μm. The material is filtered in a centrifuge to dry the mother liquor and washed 3 times to obtain a cobalt carbonate / cobalt hydroxide mixture;

[0095] (5) Primary sintering: The cobalt carbonate / cobalt hydroxide mixture obtained in step (4) was calcined in a box furnace at 350° C. for 4 h to obtain a large-particle cobalt oxide semi-finished product. The SEM image of the obtained large-particle cobalt oxide semi-finished product is as follows: Figure 6 As shown, from Figure 6 It can be seen that cobalt hydroxide is nucleated alone in the obtained large-particle cobalt oxide semi-finished product;

[0096] (6) Coating amorphous cobalt carbonate

[0097] The large-particle cobalt oxide semi-finished product obtained in step (5) and the amorphous cobalt carbonate obtained in step (2) are mixed in a spiral mixer at a mass ratio of 10:1 for 30 to 60 minutes to obtain a sample of cobalt oxide coated amorphous cobalt carbonate;

[0098] (7) Secondary sintering: the sample obtained in step (6) was calcined in a box furnace at 750° C. for 4 h to obtain a large-particle cobalt oxide product, wherein D50 was 15.8 μm and the tap density was 2.4 g / cm 3 .

Claims

1. A method for preparing large-particle cobalt tetroxide, characterized in that: The following steps are involved: (1) mixing a cobalt salt solution with a precipitant solution A containing carbonate, separating the solid and the liquid after the reaction, drying and crushing the solid phase to obtain amorphous nano-cobalt carbonate; (2) mixing the cobalt salt solution with the precipitant solution B containing carbonate and the precipitant solution C containing carbonate to react and generate cobalt carbonate particles, and then adding the amorphous nano-cobalt carbonate prepared in step (1) to react and obtain a reaction solution containing a cobalt carbonate matrix coated with the amorphous nano-cobalt carbonate; (3) under an inert atmosphere, adding a precipitant solution D containing hydroxide to the reaction solution of step (2) to adjust the pH to neutral or alkaline, then adding a cobalt salt solution and a precipitant solution D containing hydroxide, reacting to generate mixed particles, separating the solid and the liquid, taking the solid phase to obtain a cobalt carbonate / cobalt hydroxide mixture, and sintering once to obtain a large particle cobalt oxide semi-finished product; (4) mixing the large-particle cobalt oxide semi-finished product obtained in step (3) with the amorphous nano-cobalt carbonate obtained in step (1), and performing secondary sintering to obtain large-particle cobalt oxide.

2. The method for preparing large-particle cobalt tetroxide according to claim 1, characterized in that: The cobalt salt solution is at least one of a cobalt chloride solution, a cobalt nitrate solution and a cobalt sulfate solution.

3. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: The concentration of cobalt ions in the cobalt salt solution is 1.5-2.0 mol / L.

4. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: The precipitant solution A is at least one of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, and the concentration of the precipitant solution A is 250-300 g / L.

5. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: The precipitant solution B is at least one of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, and the concentration of the precipitant solution B is 60-120 g / L.

6. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: The precipitant solution C is at least one of a sodium carbonate solution, a potassium bicarbonate solution, a sodium bicarbonate solution and a potassium carbonate solution, and the concentration of the precipitant solution C is 160-240 g / L.

7. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: The precipitant solution D is at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the precipitant solution D is 320-480 g / L.

8. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (1), the cobalt salt solution is mixed with the precipitant solution A containing carbonate, with the precipitant solution A as the base solution, and then the cobalt salt solution is added.

9. The method for preparing large-particle cobalt trioxide according to claim 8, characterized in that: In step (1), the cobalt salt solution is added gradually under stirring.

10. The method for preparing large-particle cobalt trioxide according to claim 9, characterized in that: In step (1), the stirring speed is 40-50 Hz.

11. The method for preparing large-particle cobalt trioxide according to claim 10, characterized in that: In step (1), the reaction temperature is 25-30°C.

12. The method for preparing large-particle cobalt trioxide according to claim 11, characterized in that: In step (1), the pH of the reaction is 8.0-8.

5.

13. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (1), the drying and crushing is carried out using a disc-nest mill.

14. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (1), the D50 of the amorphous nano-cobalt carbonate is less than 1 μm.

15. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (2), the cobalt salt solution is mixed with the precipitant solution B containing carbonate and the precipitant solution C containing carbonate, with the precipitant solution B as the base solution, and then the cobalt salt solution and the precipitant solution C containing carbonate are added.

16. The method for preparing large-particle cobalt trioxide according to claim 15, characterized in that: In step (2), the adding of the cobalt salt solution and the precipitant solution C containing carbonate refers to first adding the cobalt salt solution and the precipitant solution C in parallel at 38-45° C., then keeping the flow rate of the cobalt salt solution unchanged, adjusting the flow rate of the precipitant solution C to control the synthesized pH to 7-8, and controlling the stirring frequency to 15-20 Hz to generate cobalt carbonate particles with a D50 of 15-16 μm.

17. The method for preparing large-particle cobalt trioxide according to claim 16, characterized in that: In step (2), the mass of the amorphous nano-cobalt carbonate added is 1 / 20-1 / 50 of the total mass of the cobalt carbonate particles and the amorphous nano-cobalt carbonate.

18. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (3), after adding the precipitant solution D containing hydroxide to the reaction solution of step (2), the reaction temperature is controlled to be 60-70° C. and the stirring frequency is 10-15 Hz.

19. The method for preparing large-particle cobalt trioxide according to claim 18, characterized in that: In step (3), the pH is adjusted to 9-10.

20. The method for preparing large-particle cobalt trioxide according to claim 19, characterized in that: In step (3), adding the cobalt salt solution and the precipitant solution D means first adding the cobalt salt solution and the precipitant solution D in parallel, then keeping the flow rate of the cobalt salt solution unchanged, and adjusting the flow rate of the precipitant solution D to control the synthesized pH to 9-10 to generate mixed particles with a D50 of 18-20 μm.

21. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (3), the primary sintering temperature is 350-450° C., and the primary sintering time is 2-4 hours.

22. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (4), the mass ratio of the large-particle cobalt oxide semi-finished product to the amorphous nano-cobalt carbonate is (10-15):

1.

23. The method for preparing large-particle cobalt trioxide according to claim 1, characterized in that: In step (4), the secondary sintering temperature is 720-750° C., and the secondary sintering time is 2-4 hours.

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