MHP coprecipitation method based on ternary precursor ratio

Abstract

The invention relates to an MHP coprecipitation method based on a ternary precursor ratio, which comprises the following steps: adjusting the ratio of nickel, cobalt and manganese contained in a solution after removing iron, aluminum and chromium, concentrating, distributing into a first mixed salt solution and a second mixed salt solution, and mixing the first mixed salt solution with ammonia water and a precipitator to form a pre-precipitation solution; and mixing the pre-precipitation solution with a second mixed salt solution, a precipitator and a complexing agent to carry out nickel-cobalt-manganese co-precipitation reaction, and promoting the sedimentation of nickel-cobalt-manganese hydroxide by controlling the reaction pH and temperature. The introduced complexing agent EDTA can utilize the stability difference of complexes of metals such as nickel, cobalt, manganese and magnesium under different pH conditions to improve the coprecipitation effect on nickel, cobalt and manganese and reduce the impurity content; meanwhile, in the coprecipitation reaction process, through a two-stage temperature setting mode, the water content of the nickel-cobalt-manganese hydroxide finished product can be effectively inhibited, and the water content is lower than 60%.

Description

Technical Field

[0001] The present invention relates to the field of hydrometallurgy, and in particular to a MHP co-precipitation method based on a ternary precursor ratio. Background Art

[0002] Nickel-cobalt-manganese ternary cathode material, usually refers to lithium nickel-cobalt-manganese oxide, with the chemical formula Li(Ni x Co y Mn (1−x−y) )O2 is a key electrode material in lithium-ion batteries, widely used in electric vehicles, mobile devices, energy storage systems, and other fields. In particular, lithium nickel cobalt manganese oxide (LNCM) is widely used in power cylindrical lithium-ion batteries due to its high energy density and excellent performance. Currently, common nickel-cobalt-manganese ternary cathode materials (NCM) include NCM523, NCM622, and NCM811, with the numbers representing the molar ratios of nickel, cobalt, and manganese.

[0003] Nickel-cobalt-manganese ternary cathode material is mainly made by sintering nickel-cobalt-manganese ternary precursor and lithium salt at high temperature. Therefore, the performance of nickel-cobalt-manganese ternary precursor largely determines the performance of the nickel-cobalt-manganese ternary cathode material synthesized from it. Nickel-cobalt-manganese ternary precursor usually refers to nickel-cobalt-manganese hydroxide, and its chemical formula is (Ni x Co y Mn (1-x-y) (OH)2) is a key intermediate product in the preparation of nickel-cobalt-manganese ternary cathode materials. With the rapid development of new energy vehicles and energy storage, the market demand for high-performance lithium-ion batteries continues to increase, driving the development of the nickel-cobalt-manganese ternary precursor market and increasing demand for nickel, cobalt, and manganese, the raw materials for the synthesis of nickel-cobalt-manganese ternary precursors.

[0004] Currently, laterite nickel ore is a key source of nickel. Containing a significant amount of cobalt and manganese, it plays a key role in the production of nickel-cobalt-manganese ternary precursors. Its abundant reserves and mineability provide a stable supply of raw materials for the development of the nickel-cobalt-manganese ternary precursor industry. Existing processes typically utilize laterite nickel ore hydrometallurgy to extract the high-purity nickel, cobalt, and manganese salts required for the preparation of nickel-cobalt-manganese ternary precursors.

[0005] In the existing wet process, the MHP (nickel cobalt hydroxide) precipitation stage (i.e., nickel cobalt hydroxide) is difficult to fully co-precipitate to ensure that the resulting nickel, cobalt, and manganese hydroxide meets the nickel, cobalt, and manganese ratios required for the ternary precursor to be prepared. Furthermore, the nickel, cobalt, and manganese hydroxide obtained in the MHP precipitation stage is high in impurities and moisture, making it unsuitable for direct use as a ternary precursor. Consequently, the nickel, cobalt, and manganese must be extracted separately after the MHP precipitation stage, such as through subsequent extraction processes. This results in lengthy and costly hydrometallurgical processes. To reduce the cost of existing laterite nickel ore hydrometallurgical processes, a new process is urgently needed to address the aforementioned shortcomings of the existing MHP precipitation stage. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and provide an MHP co-precipitation method based on the ternary precursor ratio, so as to solve the technical problem that it is difficult to co-precipitate nickel, cobalt and manganese in the MHP precipitation process section in the prior art, and to ensure that the nickel, cobalt and manganese hydroxides obtained by precipitation can meet the nickel, cobalt and manganese ratio of the ternary precursor to be prepared.

[0007] In order to achieve the above technical objectives, the technical solution provided by the present invention is: The invention provides an MHP co-precipitation method based on a ternary precursor ratio, comprising the following steps: S1, adjusting the nickel, cobalt and manganese ratio contained in a solution after iron, aluminum and chromium removal based on the nickel, cobalt and manganese ratio of the ternary precursor to be prepared, and distributing the solution into a first mixed salt solution and a second mixed salt solution after concentration; S2, uniformly mixing the first mixed salt solution, water, ammonia water and a precipitant to obtain a pre-precipitation solution; S3, simultaneously adding the second mixed salt solution, the precipitant and the complexing agent to the pre-precipitation solution to carry out a precipitation reaction, and filtering to obtain a nickel, cobalt and manganese hydroxide product; the complexing agent is ETDA.

[0008] Preferably, in step S1, the chemical formula of the ternary precursor to be prepared is Ni x Co y Mn z (OH)2, where 0.5≤x<1, 0 <y<1,0<z<1,且x+y+z=1;其镍钴锰比例可包括5:2:3、6:2:2、8:1:1、9:0.5:0.5中任意一种,待制备三元前驱体可覆盖5~9系任一三元前驱体的镍钴锰比例;具体地,可以沉镍钴后液、锰渣、锰盐等回用作为锰调节剂,以钴盐作为钴调节剂,对除铁铝铬后液中所含镍钴锰比例进行调节,使其比例与后续三元前驱体的镍钴锰比例相适应。

[0009] Preferably, in step S1, the concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution after concentration is 0.7-1.1 mol / L, and the concentration of the sum of nickel, cobalt and manganese elements in the second mixed salt solution is 0.7-1.1 mol / L.

[0010] Preferably, in step S1, the volume ratio of the first mixed salt solution to the second mixed salt solution is 1:(9-20).

[0011] Preferably, in step S2, the specific steps of step S2 are as follows: water, aqueous ammonia, and a precipitant are added to a reactor and mixed, the pH is adjusted to 9-11, the temperature is raised to 60-80°C, and the first mixed salt solution is added to the reactor and reacted for 1-2 hours to obtain a pre-precipitation solution. The concentration of the precipitant solution is 4-10 mol / L, and the concentration of the aqueous ammonia is 3-8 mol / L.

[0012] Preferably, in step S2, the precipitant includes at least one of sodium carbonate and sodium hydroxide.

[0013] Preferably, the specific steps of step S3 are as follows: the second mixed salt solution, the precipitant and the complexing agent are simultaneously added to the pre-precipitation liquid at a preset flow rate for a co-precipitation reaction, the pH is maintained at 7.5-8.5 during the reaction, the temperature is 50-70°C and does not include 70°C, and the complexing agent is added for 2-4 hours; then the temperature is rapidly raised to 70-90°C, the second mixed salt solution and the precipitant are continuously added, the pH value is maintained at 7.5-8.5, the reaction is maintained for 1-2 hours, and the nickel cobalt manganese hydroxide product is obtained after filtration.

[0014] Preferably, in step S3, the flow rate ratio of the second mixed salt solution, the precipitant, and the complexing agent is (2.6-3.0):1:(0.3-0.5).

[0015] Preferably, in step S3, the precipitant includes at least one of sodium carbonate and sodium hydroxide.

[0016] Preferably, the concentration of the complexing agent is 0.01-0.1 mol / L.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention prepares a mixed salt solution required for MHP precipitation based on the ratio of nickel, cobalt and manganese in the ternary precursor to be prepared, and divides the mixed salt solution into two parts. A small portion of the mixed salt solution is mixed with ammonia water and a precipitant to form a pre-precipitation liquid. Nickel, cobalt and manganese hydroxides are pre-generated in the pre-precipitation liquid. The pre-precipitation liquid is mixed with another mixed salt solution with a higher content and a precipitant to serve as a precipitation basis for nickel, cobalt and manganese hydroxides, thereby promoting the subsequent sedimentation of nickel, cobalt and manganese hydroxides. The introduced complexing agent EDTA can utilize the difference in complex stability of metals such as nickel, cobalt, manganese and magnesium under different pH conditions to enhance the co-precipitation effect of nickel, cobalt and manganese and reduce the impurity content. At the same time, the water content of the finished nickel, cobalt and manganese hydroxide can be effectively suppressed by setting two temperatures during the co-precipitation reaction, so that the water content is lower than 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of an embodiment of the MHP co-precipitation method based on a ternary precursor ratio of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0021] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0022] The existing hydrometallurgical process of laterite nickel ore is: ore dressing - high pressure leaching - CCD countercurrent washing - iron, aluminum and chromium removal - MHP precipitation - tailings treatment. In the MHP precipitation process, sodium hydroxide is usually added to the liquid after iron, aluminum and chromium removal to precipitate nickel and cobalt hydroxide to achieve nickel and cobalt enrichment. In the actual MHP precipitation process, the K content of nickel hydroxide is SP 2.0×10 −15 , cobalt hydroxide is K SP 5.92×10 −15, K of manganese hydroxide SP 1.9×10 −13 , K of magnesium hydroxide SP 1.8×10 −11 According to the solubility product of various metal hydroxides, it can be seen that nickel hydroxide and cobalt hydroxide have K SP Close to each other, so that they can be co-precipitated first, followed by manganese and magnesium. Since the solubility product of manganese hydroxide and nickel-cobalt hydroxide differs by two orders of magnitude, it is difficult to achieve co-precipitation of nickel, cobalt and manganese. In response to this existing problem, the present invention proposes the following solution.

[0023] The present invention provides a MHP co-precipitation method based on a ternary precursor ratio, comprising the following steps: S1, based on the nickel, cobalt and manganese ratio of the ternary precursor to be prepared, adjusting the nickel, cobalt and manganese ratio contained in the solution after iron, aluminum and chromium removal, and distributing it into a first mixed salt solution and a second mixed salt solution after concentration.

[0024] S2, uniformly mixing the first mixed salt solution, water, aqueous ammonia, and a precipitant to obtain a pre-precipitation solution.

[0025] S3, adding the second mixed salt solution, the precipitant and the complexing agent to the pre-precipitation solution simultaneously to carry out precipitation reaction, and filtering to obtain a finished nickel cobalt manganese hydroxide; the complexing agent is ETDA.

[0026] In some embodiments, in step S1, the chemical formula of the ternary precursor to be prepared is Ni x Co y Mn z (OH)2, where 0.5≤x<1, 0 <y<1,0<z<1,且x+y+z=1;其镍钴锰比例可包括5:2:3、6:2:2、8:1:1、9:0.5:0.5中任意一种,待制备三元前驱体可覆盖5~9系任一三元前驱体的镍钴锰比例;具体地,可以沉镍钴后液、锰渣、锰盐等作为锰调节剂,以钴盐作为钴调节剂,对除铁铝铬后液中所含镍钴锰比例进行调节,使其比例与后续三元前驱体的镍钴锰比例相适应。

[0027] In some embodiments, in step S1, the concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution after concentration is 0.7~1.1 mol / L, and the concentration of the sum of nickel, cobalt and manganese elements in the second mixed salt solution is 0.7~1.1 mol / L; specifically, the concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution and the second mixed salt solution after concentration is 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L or other values ​​within this range.

[0028] In some embodiments, in step S1, the volume ratio of the first mixed salt solution to the second mixed salt solution is 1:(9~20); for the distribution of the mixed salt solution, only a small amount needs to be separated as the first mixed salt solution and used to prepare the pre-precipitation solution, so that the pre-generated small amount of nickel cobalt manganese hydroxide can promote the subsequent reaction sedimentation without affecting the subsequent nickel cobalt manganese hydroxide sedimentation ratio.

[0029] In some embodiments, in step S2, the specific steps of step S2 are as follows: water, ammonia water, and a precipitant are added to a reactor and mixed, the pH is adjusted to 9-11, the temperature is raised to 60-80°C, and the first mixed salt solution is added to the reactor and reacted for 1-2 hours to obtain a pre-precipitation solution. The concentration of the precipitant solution is 4-10 mol / L, and the concentration of ammonia water is 3-8 mol / L. Specifically, in step S2, the pH can be adjusted to 9, 9.5, 10, 10.5, 11, or other values ​​within the range, the reaction temperature can be adjusted to 60°C, 65°C, 70°C, 75°C, 80°C, or other values ​​within the range, and the reaction time can be controlled to 1 hour, 1.5 hours, 2 hours, or other values ​​within the range.

[0030] In some embodiments, in step S2, the precipitant includes at least one of sodium carbonate and sodium hydroxide.

[0031] In some embodiments, the specific steps of step S3 are as follows: the second mixed salt solution, the precipitant and the complexing agent are simultaneously added to the pre-precipitation liquid at a preset flow rate for a co-precipitation reaction, the pH is maintained at 7.5-8.5 during the reaction, the temperature is 50-70°C and does not include 70°C, and the complexing agent is added for 2-4 hours; then the temperature is rapidly raised to 70-90°C, maintained for 1-2 hours, and filtered to obtain the finished nickel cobalt manganese hydroxide. Specifically, in step S3, the pH can be adjusted to 7.5, 8, 8.5 or other values ​​within the range, the temperature during the addition of the complexing agent can be adjusted to 50°C, 55°C, 60°C, 65°C, 68°C or other values ​​within the range, the time for adding the complexing agent can be controlled at 2 h, 2.5 h, 3 h, 3.5 h, 4 h or other values ​​within the range, and after the complexing agent is added, the temperature can be rapidly raised to 70°C, 75°C, 80°C, 85°C, 90°C or other values ​​within the range, and the temperature can be maintained for 1 h, 1.5 h, 2 h or other values ​​within the range.

[0032] The mechanism of the above S3 step setting is: 1) EDTA is introduced as a complexing agent. On the one hand, from the perspective of the stability constants LgK of different metal ions and complexing agents, the LgK of nickel ion is 18.56, the LgK of cobalt ion is 16.21, the LgK of manganese ion is 13.98, and the LgK of magnesium ion is 8.69. The LgK of nickel, cobalt and manganese are relatively close and differ greatly from the LgK of magnesium. Since the impurity contained in the system during the coprecipitation reaction is mainly magnesium, the stability difference between the complexing agent and nickel, cobalt, manganese and magnesium can be used to achieve preferential complexation of nickel, cobalt and manganese, thereby promoting the coprecipitation of nickel, cobalt and manganese. On the other hand, the complexing capacity of different metal ions also has a pH value range that is suitable for it. Experimental verification shows that the suitable pH range for EDTA complexing magnesium ions is 9-11. The present invention controls the pH of the coprecipitation reaction to 7.5-8.5, making the pH conditions more suitable for nickel, cobalt and manganese complexation but not for magnesium complexation, thereby further promoting the stability of the nickel, cobalt and manganese complex.

[0033] 2) Temperature has a significant effect on the complexing activity of EDTA. During the addition of the complexing agent, suitable complexing temperature conditions are maintained so that the complexing agent can better complex with nickel, cobalt and manganese. After the complexing agent is added, the temperature is quickly raised to exceed the optimal temperature conditions for the complexation of EDTA with nickel, cobalt and manganese ions, thereby inhibiting the degree of complexation and thus inhibiting the crystallization water of the complex, so that the water content of the final nickel, cobalt and manganese hydroxide product will not be too high.

[0034] In some embodiments, in step S3, the flow rate ratio of the second mixed salt solution, the precipitant, and the complexing agent is (2.6~3.0):1:(0.3~0.5), and the raw material ratio is controlled by the flow rates of the three.

[0035] In some embodiments, in step S3, the precipitant includes at least one of sodium carbonate and sodium hydroxide.

[0036] In some embodiments, the concentration of the complexing agent is 0.01-0.1 mol / L, and can be 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L or other values ​​within this range.

[0037] The present invention will be further described in detail below by way of specific examples. To avoid redundancy, the laterite nickel ore liquid after iron and aluminum removal used in the examples and comparative examples is described as follows: The laterite nickel ore iron and aluminum removal liquid used in the present invention is the liquid phase obtained after the laterite nickel ore is subjected to high-pressure acid leaching, first-stage iron and aluminum removal, and second-stage iron and aluminum removal, wherein the main components are shown in Table 1 below.

[0038] Table 1 Composition of the liquid after the second stage of iron and aluminum removal from laterite nickel ore (g / L)

[0039] Example 1 The MHP co-precipitation method based on the ternary precursor ratio in this embodiment has the following specific steps: (1) Based on the molar ratio of nickel, cobalt and manganese of the ternary precursor to be prepared being 5:2:3, the ratio of nickel, cobalt and manganese contained in the solution after removing iron, aluminum and chromium was adjusted, and after concentration, the solution was divided into a first mixed salt solution and a second mixed salt solution at a ratio of 1:20. The concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution was 0.8 mol / L, and the concentration of the sum of nickel, cobalt and manganese elements in the second mixed salt solution was 0.8 mol / L.

[0040] (2) The first mixed salt solution, water, ammonia water, and sodium hydroxide solution were mixed evenly. The concentration of the sodium hydroxide solution was 5 mol / L, and the concentration of the ammonia water was 4 mol / L. The first coprecipitation reaction was carried out at a pH of 9 and a temperature of 60°C for 1 hour to obtain a preprecipitation solution.

[0041] (3) Take EDTA with a concentration of 0.01 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.6:1:0.3. The co-precipitation reaction is carried out at a pH of 7.5 and a temperature of 50°C for 4 hours; then the temperature is quickly raised to 90°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 7.5, and the reaction is maintained for 1 hour. After filtration, the nickel cobalt manganese hydroxide product is obtained.

[0042] Example 2 The MHP co-precipitation method based on the ternary precursor ratio in this embodiment has the following specific steps: (1) Based on the molar ratio of nickel, cobalt and manganese of the ternary precursor to be prepared being 6:2:2, the ratio of nickel, cobalt and manganese contained in the solution after removing iron, aluminum and chromium was adjusted, and after concentration, the solution was divided into a first mixed salt solution and a second mixed salt solution at a ratio of 1:15. The concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution was 0.7 mol / L, and the concentration of the sum of nickel, cobalt and manganese elements in the second mixed salt solution was 0.7 mol / L.

[0043] (2) The first mixed salt solution, water, ammonia water, and sodium hydroxide solution were mixed evenly. The concentration of the sodium hydroxide solution was 4 mol / L, and the concentration of the ammonia water was 5 mol / L. The first coprecipitation reaction was carried out at a pH of 10 and a temperature of 70°C for 1 hour to obtain a preprecipitation solution.

[0044] (3) Take EDTA with a concentration of 0.05 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.8:1:0.4. The co-precipitation reaction is carried out at a pH of 8.0 and a temperature of 60°C for 2 hours; then the temperature is quickly raised to 70°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 8.0, and the reaction is maintained for 1.5 hours. After filtration, the nickel cobalt manganese hydroxide product is obtained.

[0045] Example 3 The MHP co-precipitation method based on the ternary precursor ratio in this embodiment has the following specific steps: (1) Based on the molar ratio of nickel, cobalt and manganese of the ternary precursor to be prepared being 8:1:1, the ratio of nickel, cobalt and manganese contained in the solution after removing iron, aluminum and chromium was adjusted, and after concentration, the solution was divided into a first mixed salt solution and a second mixed salt solution in a ratio of 1:12. The concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution was 0.8 mol / L, and the concentration of the sum of nickel, cobalt and manganese elements in the second mixed salt solution was 0.8 mol / L.

[0046] (2) The first mixed salt solution, water, ammonia water, and sodium hydroxide solution were mixed evenly. The concentration of the sodium hydroxide solution was 5 mol / L, and the concentration of the ammonia water was 7 mol / L. The first coprecipitation reaction was carried out at a pH of 10.5 and a temperature of 70°C for 1 hour to obtain a preprecipitation solution.

[0047] (3) Take EDTA with a concentration of 0.05 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.9:1:0.3. The co-precipitation reaction is carried out at a pH of 8.0 and a temperature of 60°C for 4 hours; then the temperature is quickly raised to 90°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 8.0, and the reaction is maintained for 1 hour. After filtration, the finished nickel-cobalt-manganese hydroxide is obtained.

[0048] Example 4 The MHP co-precipitation method based on the ternary precursor ratio in this embodiment has the following specific steps: (1) Based on the molar ratio of nickel, cobalt and manganese in the ternary precursor to be prepared of 9:0.5:0.5, the ratio of nickel, cobalt and manganese in the solution after removing iron, aluminum and chromium was adjusted. After concentration, the solution was divided into a first mixed salt solution and a second mixed salt solution in a ratio of 1:9. The concentration of the sum of nickel, cobalt and manganese in the first mixed salt solution was 1.1 mol / L, and the concentration of the sum of nickel, cobalt and manganese in the second mixed salt solution was 1.1 mol / L.

[0049] (2) The first mixed salt solution, water, ammonia water, and sodium hydroxide solution were mixed evenly. The concentration of the sodium hydroxide solution was 10 mol / L and the concentration of the ammonia water was 8 mol / L. The first coprecipitation reaction was carried out at a pH of 11 and a temperature of 75°C for 1 hour to obtain a preprecipitation solution.

[0050] (3) Take EDTA with a concentration of 0.1 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 3.0:1:0.5. The co-precipitation reaction is carried out at a pH of 8.5 and a temperature of 70°C for 3 hours; then the temperature is quickly raised to 80°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 8.5, and the reaction is maintained for 2 hours. After filtration, the nickel cobalt manganese hydroxide product is obtained.

[0051] Comparative Example 1 (without pre-precipitation solution) The specific steps in this comparative example are as follows: (1) Based on the molar ratio of nickel, cobalt and manganese of the ternary precursor to be prepared being 8:1:1, the ratio of nickel, cobalt and manganese contained in the solution after removing iron, aluminum and chromium was adjusted, and after concentration, the solution was divided into a mixed salt solution at a ratio of 1:12. The concentration of the sum of nickel, cobalt and manganese elements in the mixed salt solution was 0.8 mol / L.

[0052] (2) Take EDTA with a concentration of 0.05 mol / L, and add the mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.9:1:0.3. The co-precipitation reaction is carried out at a pH of 8.0 and a temperature of 60°C for 4 hours; then the temperature is quickly raised to 90°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 8.0, and the reaction is maintained for 1 hour. After filtration, the finished nickel-cobalt-manganese hydroxide is obtained.

[0053] Comparative Example 2 (no temperature increase after adding complexing agent) This comparative example is based on the steps of Example 3, with only step (3) adjusted as follows: (3) Take EDTA with a concentration of 0.05 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.9:1:0.3. The precipitation reaction is carried out at a pH of 8.0 and a temperature of 60°C for 4 hours; then, the temperature is maintained at 60°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 8.0, and the reaction is continued for 1 hour. After filtration, the nickel cobalt manganese hydroxide product is obtained.

[0054] Comparative Example 3 (pH too high during complexation reaction) This comparative example is based on the steps of Example 3, with only step (3) adjusted as follows: (3) Take EDTA with a concentration of 0.05 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.9:1:0.3. The co-precipitation reaction is carried out at a pH of 9.5 and a temperature of 60°C for 4 hours; then the temperature is quickly raised to 90°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 9.5, and the reaction is maintained for 1 hour. After filtration, the nickel cobalt manganese hydroxide product is obtained.

[0055] Comparative Example 4 (Temperature is too high during complexation reaction) This comparative example is based on the steps of Example 3, with only step (3) adjusted as follows: (3) Take EDTA with a concentration of 0.05 mol / L, and add the second mixed salt solution, sodium hydroxide solution and EDTA to the pre-precipitation solution at a flow rate ratio of 2.9:1:0.3. The co-precipitation reaction is carried out at a pH of 8.0 and a temperature of 90°C for 4 hours; then the temperature is quickly raised to 90°C, and the second mixed salt solution and precipitant are continuously added. The pH value is maintained at 8.0, and the reaction is maintained for 1 hour. After filtration, the nickel cobalt manganese hydroxide product is obtained.

[0056] Test Case The molar ratio of nickel, cobalt and manganese, the mass fraction of magnesium and the water content of the nickel, cobalt and manganese hydroxide products prepared in Examples 1 to 4 and Comparative Examples 1 to 4 are specifically shown in Table 2.

[0057] Table 2

[0058] As can be seen from Examples 1 to 4, the prepared nickel-cobalt-manganese hydroxide product has a very close ratio of the nickel-cobalt-manganese substances to the initial ternary precursor to be prepared, which proves that the MHP co-precipitation method based on the ternary precursor ratio described in the present invention can well achieve nickel-cobalt-manganese co-precipitation; at the same time, the magnesium impurity content is low and the water content can be controlled at a level below 60%.

[0059] By comparing the finished nickel-cobalt-manganese hydroxide products prepared in Example 3 and Comparative Example 1, the mass percentage of Ni in Comparative Example 1 was reduced by 8%, the mass percentage of Co was reduced by 5%, and the mass percentage of Mn was reduced by 9% compared with Example 3, demonstrating that if the pre-precipitation solution is not introduced during the complex reaction, the precipitation rate of nickel-cobalt-manganese will be reduced.

[0060] Comparing Example 3 with Comparative Example 2, it can be seen that in Comparative Example 2, compared with Example 3, the temperature is not increased after the complexing agent is added, so that the complexing process of EDTA is not inhibited during the latter stage of the reaction, and the water content of the final nickel-cobalt-manganese hydroxide product is significantly increased.

[0061] By comparing Example 3 with Comparative Example 3, it can be seen that in Comparative Example 3, the pH is increased during the complexation reaction relative to Example 3, so that the degree of complexation of EDTA with nickel, cobalt and manganese is reduced, while the degree of complexation with magnesium is increased, thereby causing the molar ratio of nickel, cobalt and manganese to fluctuate, and the magnesium impurity content is significantly increased.

[0062] By comparing the finished nickel-cobalt-manganese hydroxide products prepared in Example 3 and Comparative Example 4, the mass percentage of Ni in Comparative Example 4 was reduced by 6%, the mass percentage of Co was reduced by 2%, and the mass percentage of Mn was reduced by 8% relative to Example 3. This indicates that in Comparative Example 4, the reaction temperature was increased during the complexation reaction relative to Example 3, so that the temperature conditions exceeded the suitable complexation range of EDTA for nickel, cobalt and manganese, reducing the degree of complexation of nickel, cobalt and manganese by EDTA, thereby reducing the precipitation rate of nickel, cobalt and manganese.

[0063] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A MHP co-precipitation method based on a ternary precursor ratio, characterized in that: The following steps are involved: S1, adjusting the nickel, cobalt and manganese ratios in the solution after iron, aluminum and chromium removal based on the nickel, cobalt and manganese ratios of the ternary precursor to be prepared, and concentrating and distributing the solution into a first mixed salt solution and a second mixed salt solution; S2, uniformly mixing the first mixed salt solution, water, aqueous ammonia, and a precipitant to obtain a pre-precipitation solution; S3, adding the second mixed salt solution, precipitant and complexing agent to the pre-precipitation solution simultaneously to carry out precipitation reaction, and filtering to obtain a finished nickel-cobalt-manganese hydroxide product; The complexing agent is ETDA.

2. The MHP co-precipitation method based on a ternary precursor ratio according to claim 1, characterized in that: In the step S1, the chemical formula of the ternary precursor to be prepared is Ni x Co y Mn z (OH)2, where 0.5 ≤ x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1.

3. The MHP co-precipitation method based on a ternary precursor ratio according to claim 1, characterized in that: In the step S1, after concentration, the concentration of the sum of nickel, cobalt and manganese elements in the first mixed salt solution is 0.7-1.1 mol / L, and the concentration of the sum of nickel, cobalt and manganese elements in the second mixed salt solution is 0.7-1.1 mol / L.

4. The MHP co-precipitation method based on a ternary precursor ratio according to claim 3, characterized in that: In step S1, the volume ratio of the first mixed salt solution to the second mixed salt solution is 1:(9-20).

5. The MHP co-precipitation method based on the ternary precursor ratio according to claim 4, characterized in that: In the step S2, the specific steps of the step S2 are as follows: Add water, ammonia water, and a precipitant into a reactor and mix, adjust the pH to 9-11, raise the temperature to 60-80° C., then add the first mixed salt solution into the reactor and react for 1-2 hours to obtain the pre-precipitation solution; The concentration of the precipitant solution is 4-10 mol / L, and the concentration of the ammonia water is 3-8 mol / L.

6. The MHP co-precipitation method based on a ternary precursor ratio according to claim 4, characterized in that: In the step S2, the precipitant includes at least one of sodium carbonate and sodium hydroxide.

7. The MHP co-precipitation method based on a ternary precursor ratio according to claim 1, characterized in that: The specific steps of the S3 step are as follows: The second mixed salt solution, the precipitant and the complexing agent are simultaneously added to the pre-precipitation liquid at a preset flow rate to carry out a co-precipitation reaction. During the reaction, the pH is maintained at 7.5-8.5, the temperature is 50-70° C. and excluding 70° C., and the complexing agent is added for 2-4 hours; then the temperature is rapidly raised to 70-90° C., the second mixed salt solution and the precipitant are continuously added, the pH value is maintained at 7.5-8.5, the reaction is maintained for 1-2 hours, and the nickel cobalt manganese hydroxide product is obtained after filtration.

8. The MHP co-precipitation method based on a ternary precursor ratio according to claim 7, characterized in that: In the step S3, the flow rate ratio of the second mixed salt solution, the precipitant, and the complexing agent is (2.6-3.0):1:(0.3-0.5).

9. The MHP co-precipitation method based on a ternary precursor ratio according to claim 7, characterized in that: In the step S3, the precipitant includes at least one of sodium carbonate and sodium hydroxide.

10. The MHP co-precipitation method based on a ternary precursor ratio according to claim 7, characterized in that: The concentration of the complexing agent is 0.01-0.1 mol / L.

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