Leaching methods for high-grade nickel matte, precursors for cathode materials, preparation methods, and applications

Abstract

This invention discloses a leaching method for high-grade nickel matte, a cathode material precursor, its preparation method, and its applications, relating to the fields of pyrometallurgy and hydrometallurgy. High-grade nickel matte undergoes a self-thermal reaction with an oxidant. The oxidant serves as a raw material, providing oxidation, while the heat generated by the self-thermal reaction replaces the external heat source. The pre-treated powder can undergo a single low-acid leaching under normal pressure. Because the material after the self-thermal reaction of high-grade nickel matte and the oxidant potassium permanganate is readily leached with acid, it requires minimal auxiliary materials for low-acid leaching and eliminates the need for high-acidity leaching, thus reducing costs. Compared to conventional high-pressure oxygen leaching, the leaching process provided by this invention has lower equipment requirements, shorter leaching time, and higher leaching efficiency. During the reaction, most of the high-grade nickel matte forms nickel oxide.

Description

Technical Field

[0001] This invention relates to the fields of pyrometallurgy and hydrometallurgy, and more specifically, to a leaching method for high-grade nickel matte, a cathode material precursor, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy technologies, the demand for high-nickel products is increasing. Providing new nickel sources has a stabilizing effect on the industrial chain system. High-grade nickel matte and nickel iron are good choices for new nickel sources.

[0003] High-grade nickel matte is a eutectic melt of nickel, copper, cobalt, iron, and sulfur metal sulfides, produced from nickel concentrate through electro- and rotary primary smelting. The nickel, copper, and cobalt phases mainly exist as sulfide and alloy phases. It is called high-grade nickel matte because of its high nickel content (55%-65%), while low-grade nickel matte has a lower nickel content. It is mainly used in the production of electrolytic nickel, nickel oxide, ferronickel, nickel-containing alloys, and various nickel salts. After special treatment, it can also be used directly in steelmaking. Ferro-nickel (NPI) is an important ferronickel alloy product, typically containing about 4-10% nickel. It is mainly used in stainless steel production, alloy steel, high-temperature alloys, and battery materials. Its main raw material is ferronickel ore, which contains both nickel and iron and is commonly found in the Philippines, Indonesia, and New Caledonia. It is clear that high-grade nickel matte is merely a transitional process; the ultimate goal is to produce nickel sulfate, which is an essential material for the production of ternary precursors, ultimately forming the cathode material of batteries. Starting with natural nickel ore and eventually reaching the cathode material, the process involves a complex and lengthy manufacturing process, with each process potentially becoming a sub-sector within it.

[0004] The leaching of high-grade nickel matte typically employs a high-pressure acid leaching process. High-pressure acid leaching places stringent requirements on equipment operating conditions, generates large amounts of slag, requires bulky equipment, has high manufacturing costs, and carries low safety risks. Traditional low-acid leaching of high-grade nickel matte, on the other hand, achieves a leaching rate of only 20% to 50% in a single pass and is time-consuming. Therefore, a more efficient, faster, safer, and more economical leaching method is needed. Furthermore, if oxidation roasting is used in the pretreatment of high-grade nickel matte, an additional heat source is required, resulting in high energy consumption and economic costs.

[0005] Furthermore, commercially available ternary precursors are hydroxides composed of nickel, cobalt, and manganese, with the proportions of each element determining the precursor's performance. With the rapid development of the new energy vehicle industry and the resulting surge in demand for high-capacity lithium-ion batteries, the performance requirements for front-end ternary cathode materials have been raised, leading to the increasing dominance of high-nickel ternary precursors. Developing new leaching methods to reduce the cost of synthesizing ternary precursors is a key direction for the industry.

[0006] In summary, there is an urgent need to develop an efficient, fast, safe, and economical high-grade nickel matte leaching process to significantly improve the leaching rate while reducing process costs.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a high-grade nickel matte leaching method, a cathode material precursor and its preparation method and application, aiming to significantly improve the leaching rate while reducing process costs.

[0009] This invention is implemented as follows:

[0010] In a first aspect, the present invention provides a leaching method for high-grade nickel matte, comprising:

[0011] Raw material pretreatment: High-grade nickel matte is mixed with an oxidant and subjected to an autothermal reaction;

[0012] One-time low-acid leaching: The powder obtained from the pretreatment of raw materials is subjected to one-time low-acid leaching under non-pressurized conditions, and the pH value of the leaching is controlled at 0.5-1.0.

[0013] In an optional embodiment, the raw material pretreatment process includes: performing a first magnetic separation on high-grade nickel matte to obtain nickel-iron element and high-grade nickel matte powder; mixing the high-grade nickel matte powder with an oxidant and a buffer to carry out an autothermal reaction to obtain pretreatment intermediate powder; and performing a second magnetic separation on the pretreatment intermediate powder to obtain pretreatment powder.

[0014] During the raw material pretreatment process, at least one of the following characteristics A1-A7 must be satisfied:

[0015] Feature A1: First, the high-grade nickel matte is crushed to a particle size of 100-400 mesh, and then subjected to magnetic separation.

[0016] Feature A2: The oxidant is selected from at least one of potassium permanganate and sodium permanganate;

[0017] Feature A3: The mass ratio of high-grade nickel matte powder to oxidant is 1:(1-3);

[0018] Feature A4: The buffer is selected from at least one of calcium carbonate and calcium hydroxide;

[0019] Feature A5: The mass ratio of buffer to total amount of high-grade nickel matte powder and oxidant is (1-10):100;

[0020] Feature A6: The reaction time for the self-heating reaction is 50 min-120 min;

[0021] Feature A7: The self-heating reaction takes place in an air atmosphere.

[0022] In an optional embodiment, a single low-acid leaching process includes: leaching the pretreated powder in a sulfuric acid solution;

[0023] After reacting for 1-2 hours, the first solid-liquid separation is performed;

[0024] Alternatively, after reacting for 1-2 hours, add pre-treated powder to adjust the pH value to 2.0-2.5, react for 2-3 hours, and then perform the first solid-liquid separation.

[0025] Alternatively, after reacting for 0.5-2.0 hours, crude nickel hydroxide or crude cobalt hydroxide can be added to adjust the pH to 2.0-2.5, react for 2-3 hours, and then perform the first solid-liquid separation.

[0026] In an optional embodiment, the pretreatment powder is mixed with water and concentrated sulfuric acid, and the resulting slurry is reacted under conditions with a pH of 0.5-1.0.

[0027] During a single low-acid leaching process, at least one of the following characteristics B1-B5 must be satisfied:

[0028] Feature B1: The mass ratio of pretreatment powder to water is 1:(1-4);

[0029] Feature B2: The mass ratio of pretreatment powder to concentrated sulfuric acid is 1:(1.0-1.5), and the mass fraction of concentrated sulfuric acid is greater than or equal to 98%;

[0030] Feature B3: The reaction temperature for a single low-acid leaching is 50℃-90℃;

[0031] Feature B4: Before the first solid-liquid separation, the temperature of the material after the reaction is completed is adjusted to 80℃-90℃;

[0032] Feature B5: The first solid-liquid separation is carried out in a diaphragm filter press.

[0033] In an optional embodiment, the method further includes: mixing the primary low-acid leaching residue obtained from the first solid-liquid separation with sulfuric acid to adjust the pH value to 0.5-1.0, adjusting the temperature to 50℃-70℃, and then mixing and reacting it with a reducing agent; repeatedly adding sulfuric acid and reducing agent to adjust the pH value to 0.5-1.0, and performing a secondary low-acid leaching.

[0034] Preferably, after the secondary low-acid leaching reaction is completed, a second solid-liquid separation is performed to obtain secondary low-acid leaching solution and secondary low-acid leaching residue; the secondary low-acid leaching solution is returned to the primary low-acid leaching stage and mixed with the pre-treated powder to form a pulp.

[0035] Preferably, the reducing agent is a hydrogen peroxide solution with a mass fraction of 8%-30%.

[0036] In an optional embodiment, the low-acid leachate obtained from the first solid-liquid separation is subjected to copper removal, ferrous removal, and iron-aluminum removal in sequence to obtain a purified leachate.

[0037] Preferably, the copper removal process includes: mixing a primary low-acid leaching solution with elemental nickel or nickel-iron powder and reacting for 1-2 hours, then adding sulfuric acid to adjust the pH to 0.5-1.0, and letting it stand for 2-4 hours to obtain the copper-removed solution.

[0038] More preferably, the pH value is stabilized for 1-4 hours under stirring before standing for 2-4 hours;

[0039] More preferably, by adjusting the amount of nickel-iron element or nickel-iron powder added, the molar ratio of the total amount of nickel-iron added to the copper ions in the primary low-acid leaching solution is 1:(0.5-1.5).

[0040] More preferably, the particle size of the nickel-iron powder is 60-200 mesh.

[0041] In an optional embodiment, the solution after copper removal is mixed with hydrogen peroxide solution to remove ferrous iron, heated to 80℃-95℃ and adjusted to pH 3.8-4.5 to remove iron and aluminum to a deeper level, and then calcium, magnesium, zinc and copper are removed by extraction.

[0042] Preferably, the process of removing ferrous ions includes: heating the solution after the first copper removal to 80℃-95℃, adding nickel hydroxide to adjust the pH to 2.0-3.0, and adding hydrogen peroxide solution with a mass fraction of 8%-30% to remove the remaining ferrous ions;

[0043] Preferably, the pH value is adjusted to 3.8-4.5 by adding sodium carbonate solution.

[0044] Secondly, the present invention provides a method for preparing a cathode material precursor, comprising using the leachate obtained by any of the leaching methods in the foregoing embodiments as raw material and preparing the cathode material precursor by co-precipitation method;

[0045] Preferably, a metal salt is added to the leachate, and a complexing agent and a precipitant are added during the co-precipitation reaction.

[0046] Thirdly, the present invention provides a cathode material precursor, which is prepared by the preparation method described in the foregoing embodiments.

[0047] Fourthly, the present invention provides a cathode material prepared by means of the cathode material precursor described in the foregoing embodiments.

[0048] This invention offers the following advantages: High-grade nickel matte undergoes a self-thermal reaction with an oxidant. The oxidant, acting as a raw material, provides oxidation, while the heat generated by the self-thermal reaction replaces the external heat source. The pre-treated powder can undergo a single low-acid leaching under normal pressure. Because the material resulting from the self-thermal reaction of high-grade nickel matte and the oxidant potassium permanganate is readily leached with acid, it requires minimal auxiliary materials for low-acid leaching and eliminates the need for high-acidity leaching, thus reducing costs. Compared to conventional high-pressure oxygen leaching, the leaching process provided by this invention has lower equipment requirements, shorter leaching time, and higher leaching efficiency. During the reaction, most of the high-grade nickel matte forms nickel oxide. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a flowchart of the high-grade nickel matte leaching method according to an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0052] To address the problems of low leaching rate and high process cost caused by the need for high pressure assistance in traditional high-grade nickel matte leaching processes, the inventors optimized the high-grade nickel matte leaching method and specifically adjusted the steps of the raw material pretreatment process, so that the pretreated powder obtained from the raw material pretreatment process can be leached under normal pressure conditions, and the leaching rate is significantly improved.

[0053] Please refer to Figure 1 This invention provides a leaching method for high-grade nickel matte, comprising the following steps:

[0054] S1. Raw material pretreatment

[0055] The raw material pretreatment process provided in this invention mainly includes the following three steps: primary magnetic separation, autothermal reaction, and secondary magnetic separation. High-grade nickel matte mainly contains alloy phases and sulfide phases. Primary magnetic separation removes elemental nickel-iron, enriching the sulfide phase for autothermal reaction. The difficult-to-leach sulfides in the high-grade nickel matte are essentially oxidized, greatly improving leaching efficiency. After the reaction, the iron sulfide in the sulfide phase reacts to form magnetite (Fe3O4), which is then removed by secondary magnetic separation.

[0056] In some embodiments, high-grade nickel matte is pulverized to a particle size of 100-400 mesh (e.g., 100 mesh, 200 mesh, 300 mesh, 400 mesh, etc.), and then subjected to a magnetic separation to obtain elemental nickel-iron and high-grade nickel matte powder. Utilizing the smaller particle size of the high-grade nickel matte for a single magnetic separation ensures thorough removal of elemental nickel-iron, improving the purification effect. Specifically, the first magnetic separation can be performed in a commercially available magnetic separator, with the separation parameters set according to the equipment's built-in optimal parameters. The elemental nickel-iron powder obtained from the first magnetic separation can be used for copper removal in subsequent impurity removal processes, thus reducing the elemental content in the high-grade nickel matte, increasing its utilization rate, reducing auxiliary material consumption, and consequently reducing the oxidant required for the magnetically separated high-grade nickel matte powder, resulting in lower process costs.

[0057] The high-grade nickel matte powder obtained from the first magnetic separation is mixed with an oxidant and a buffer and subjected to an autothermal reaction to obtain a pre-treatment intermediate powder. This intermediate powder is then subjected to a second magnetic separation to obtain the pre-treated powder. In conventional leaching methods, the presence of small amounts of oil and iron in the low-acid leaching slurry during pressure filtration can affect the filtration process of a diaphragm filter press. However, in this embodiment of the invention, the high temperature generated by the autothermal reaction promotes the decomposition of organic matter, and the iron is converted into magnetite (Fe3O4), which is then removed by magnetic separation, resulting in lower costs and solving the problem of difficult pressure filtration. Furthermore, the second magnetic separation also reduces impurities in the low-acid leaching raw material, lowering the cost of subsequent iron removal.

[0058] In some embodiments, the oxidant is selected from at least one of potassium permanganate and sodium permanganate, and the oxidant can be any one or more of the above. The mass ratio of high-grade nickel matte powder to oxidant is 1:(1-3), such as 1:1, 1:2, 1:3, etc. The high-grade nickel matte powder and oxidant undergo a self-heating reaction, and the heat of the reaction process is provided by the reaction itself, saving a lot of electricity. The reaction speed is faster than traditional heating methods. By adjusting the raw material ratio, the combustion reaction can be made more complete, and the core temperature can reach over 1000°C.

[0059] In some embodiments, the buffer is selected from at least one of calcium carbonate and calcium hydroxide, and the buffer can be any one or more of the above. The mass ratio of the buffer to the total amount of high-grade nickel matte powder and oxidant is (1-10):100. The amount of buffer used is calculated based on the total amount of high-grade nickel matte powder and oxidant, so that the mass ratio of the buffer to the total amount of high-grade nickel matte powder and oxidant can be 1:100, 3:100, 5:100, 8:100, 10:100, etc. The addition of buffers such as calcium carbonate in the pretreatment process can not only regulate the autothermal reaction rate and reduce the reaction risk factor, but also absorb the sulfur dioxide generated by the reaction of high-grade nickel matte and oxidant, greatly reducing the safety risks of the process and better meeting environmental protection requirements.

[0060] In some embodiments, the reaction time of the self-heating reaction is 50 min-120 min, specifically 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc. The reaction is terminated when the oxidant or high-grade nickel matte is completely consumed. The self-heating reaction can be carried out in an air atmosphere, which is convenient to operate.

[0061] It should be added that, compared with the use of lithium cobalt oxide or ternary cathode materials as auxiliary materials for calcination in high-grade nickel matte, the oxidant potassium permanganate in this embodiment of the invention has a single phase, does not contain copper, iron or aluminum impurities, and its oxidizing power is much higher than that of ternary cathode materials. The pretreatment process adopts two magnetic separations, which is lower in cost than calcination. The alloy phase nickel-iron element obtained by the first magnetic separation can be used for the subsequent first copper removal, and the second magnetic separation removes iron tetroxide. While removing impurities, the extraction process does not need to consider lithium recovery at the back end, and the overall process route is optimized and upgraded.

[0062] S2, single low-acid leaching

[0063] The pretreated powder is subjected to a low-acid leaching under non-pressurized conditions, with the leaching pH controlled at 0.5-1.0. Since the material after the self-thermal reaction of high-grade nickel matte with oxidants such as potassium permanganate is readily leached with acid, it requires minimal auxiliary materials to assist in low-acid leaching, and also eliminates the need for high-acidity leaching, thus reducing process costs. Compared to conventional high-pressure oxygen leaching, this method has lower equipment requirements, shorter leaching time, and improved leaching efficiency, with most of the high-grade nickel matte forming nickel oxide during the reaction. Although the method provided in this embodiment is atmospheric pressure leaching, its leaching efficiency is close to that of high-pressure leaching, requiring simpler equipment and resulting in lower costs.

[0064] Specifically, the leaching pH value for a single low-acid leaching can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc.

[0065] In some embodiments, the pretreatment powder is mixed with water and concentrated sulfuric acid, and the resulting slurry is reacted under conditions of pH 0.5-1.0. Since the reactor (e.g., crucible) is at a high temperature after the self-heating reaction, the crucible can be used to mix water with part of the pretreatment powder to form a slurry. Water can be sprayed into the crucible to cool it down, and the residual heat can be used to indirectly raise the temperature, reducing the amount of steam required for subsequent heating of the liquid. The resulting slurry is then introduced into the corresponding reaction tank for batching.

[0066] In some embodiments, during a single low-acid leaching process, the mass ratio of pretreatment powder to water is 1:(1-4), such as 1:1, 1:2, 1:3, 1:4, etc. The mass ratio of pretreatment powder to concentrated sulfuric acid is 1:(1.0-1.5), such as 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc., and the mass fraction of concentrated sulfuric acid is greater than or equal to 98%, such as commercially available 98% concentrated sulfuric acid. By adjusting the amounts of pretreatment powder, water, and concentrated sulfuric acid, the reaction is made sufficient, thereby increasing the nickel leaching rate.

[0067] Furthermore, the reaction temperature for a single low-acid leaching is 50℃-90℃, such as 50℃, 60℃, 70℃, 80℃, 90℃, etc. Within this temperature range, it is beneficial to further improve the leaching effect.

[0068] In some embodiments, a single low-acid leaching process can be employed using the following three methods:

[0069] (1) After reacting for 1-2 hours, the first solid-liquid separation is carried out to obtain a low-acid leaching residue and a low-acid leaching solution. Specifically, the reaction time can be 1 hour, 2 hours, 3 hours, etc.

[0070] (2) After reacting for 1-2 hours, add pretreatment powder to adjust the pH value to 2.0-2.5, react for 2-3 hours, and then perform the first solid-liquid separation. Specifically, after adding pretreatment powder to adjust the pH value, the pH value can be 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, etc., and the reaction time can be 2.0 hours, 2.5 hours, 3.0 hours, etc.

[0071] (3) After reacting for 0.5-2.0 hours, add crude nickel hydroxide (MHP) or crude cobalt hydroxide to adjust the pH to 2.0-2.5, react for 2-3 hours, and then perform the first solid-liquid separation. The crude nickel hydroxide (MHP) or crude cobalt hydroxide is a commercially available raw material. After adjusting the pH, the pH can be 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, etc., and the reaction time can be 2.0 hours, 2.5 hours, 3.0 hours, etc.

[0072] Of the three processes mentioned above, processes (2) and (3) can further improve the leaching rate and increase the utilization rate of raw materials.

[0073] In some embodiments, before the first solid-liquid separation, the temperature of the material after the reaction is adjusted to 80℃-90℃, such as 80℃, 83℃, 85℃, 88℃, 90℃, etc. Because the slurry concentration is high, crystallization easily occurs at low temperatures, clogging the solid-liquid separation equipment. Appropriately raising the temperature before solid-liquid separation can prevent crystallization. The first solid-liquid separation can be carried out in a diaphragm filter press, but is not limited to this.

[0074] S3, Primary low-acid leaching residue treatment

[0075] The residue from a single low-acid leaching process still contains a small amount of valuable metals, which can be used for a second low-acid leaching process to improve the utilization rate of raw materials.

[0076] In some embodiments, the primary low-acid leaching residue obtained from the first solid-liquid separation is mixed with sulfuric acid to adjust the pH to 0.5-1.0. After adjusting the temperature to 50℃-70℃, it is mixed with a reducing agent and reacted. After adding the reducing agent, the pH rises, requiring the addition of sulfuric acid to adjust the pH again. This process of adding sulfuric acid and reducing agent is repeated until the pH is maintained at 0.5-1.0, resulting in a secondary low-acid leaching. The primary low-acid leaching residue contains high-valence manganese; by adding sulfuric acid and a reducing agent for secondary leaching, the leaching rate of valuable metals is improved. Specifically, the leaching pH for the secondary low-acid leaching can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc., and the leaching temperature can be 50℃, 55℃, 60℃, 65℃, 70℃, etc.

[0077] In some embodiments, the reducing agent is a hydrogen peroxide solution with a mass fraction of 8%-30%, and the specific mass fraction can be 8%, 10%, 15%, 20%, 25%, 30%, etc.

[0078] In some embodiments, after the secondary low-acid leaching reaction is completed, a second solid-liquid separation is performed to obtain secondary low-acid leaching solution and secondary low-acid leaching residue. The secondary low-acid leaching solution is returned to the primary low-acid leaching stage and mixed with pretreatment powder to form a pulp to recover manganese.

[0079] S4, Primary low-acid leachate treatment

[0080] The low-acid leachate obtained from the first solid-liquid separation is subjected to copper removal, ferrous removal, and iron-aluminum removal in sequence to obtain a purified leachate, which can be directly used to prepare cathode material precursors.

[0081] In some embodiments, the copper removal process includes: mixing a primary low-acid leaching solution with elemental nickel-iron or nickel-iron powder and reacting for 1-2 hours; then adding sulfuric acid to adjust the pH to 0.5-1.0; stabilizing the pH under stirring for 1-4 hours; and then allowing the solution to stand for 2-4 hours to age the fine sponge copper, resulting in a primary copper removal solution. Elemental nickel-iron is the material obtained after primary magnetic separation, and the nickel-iron powder can be commercially available NPI powder. Compared to traditional copper removal using iron powder in leaching solutions, this embodiment of the invention uses nickel-iron powder for copper removal, providing a new nickel source while achieving copper removal, and also reducing the introduction of iron impurities into the system, significantly reducing the cost of subsequent impurity removal and solid waste iron-aluminum slag treatment.

[0082] It should be noted that the copper removal effect of nickel-iron powder is similar to that of iron powder, but some unreacted nickel-iron powder will remain in the generated sponge copper, resulting in substandard sponge copper. The nickel-iron elemental powder used in this embodiment of the invention is mainly derived from high-grade nickel matte powder after one magnetic separation. After adding a certain amount of nickel-iron powder to remove copper, acid is added to lower the pH value to consume the small amount of residual nickel-iron powder. This not only improves the utilization rate of high-grade nickel matte raw materials but also saves iron powder auxiliary materials and ensures the quality of sponge copper.

[0083] Specifically, the reaction time for mixing low-acid leaching solution with elemental nickel-iron or nickel-iron powder can be 1.0h, 1.5h, 2.0h, etc.; then sulfuric acid is added to adjust the pH value to 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc.; the stabilization time can be 1h, 2h, 3h, 4h, etc.; no stirring is performed during standing, and the standing time can be 2h, 3h, 4h, 5h, etc.

[0084] In some embodiments, by adjusting the amount of nickel-iron element or nickel-iron powder added, the molar ratio of the total amount of nickel-iron added to copper ions in the primary low-acid leaching solution is 1:(0.5-1.5), such as 1:0.5, 1:0.8, 1:1.0, 1:1.2, 1:1.5, etc. Controlling the total amount of nickel-iron within the above range can more fully displace copper and improve the impurity removal effect.

[0085] Furthermore, the particle size of nickel-iron powder is 60-200 mesh. Commercially available nickel-iron powder (NPI) can be pulverized before being used for copper removal.

[0086] In some embodiments, the copper-removing solution after the first copper removal is mixed with hydrogen peroxide solution to remove ferrous iron. The temperature is then raised to 80℃-95℃, and the pH is adjusted to 3.8-4.5 for further iron and aluminum removal. Subsequently, calcium, magnesium, zinc, and copper are removed using extraction. Optimizing the impurity removal process further removes impurities from the leachate, improving product purity and avoiding the influence of impurity elements. Specifically, the amount of hydrogen peroxide solution added can be calculated based on the ferrous iron content in the leachate. The reaction temperature for deep iron and aluminum removal can be controlled at 80℃, 85℃, 90℃, 95℃, etc., and the specific pH value can be controlled at 3.8, 4.0, 4.2, 4.5, etc., which can be adjusted by adding sodium carbonate solution.

[0087] In some embodiments, the ferrous removal process includes: heating the solution after the first copper removal to 80℃-95℃, adding crude nickel hydroxide to adjust the pH to 2.0-3.0, and adding a hydrogen peroxide solution with a mass fraction of 8%-30% to remove remaining ferrous ions. Using crude nickel hydroxide (MHP) to adjust the pH has three advantages: it utilizes the reaction between ferrous ions and the difficult-to-leach high-valence manganese slag in MHP, effectively oxidizing the ferrous ions and improving the MHP leaching effect; it also consumes the residual acid from the first copper removal; and it saves on soda ash (i.e., sodium carbonate). The amount of hydrogen peroxide solution added is calculated based on the ferrous content and the amount of nickel hydroxide in the solution after the first copper removal, aiming to achieve sufficient ferrous removal.

[0088] In summary, compared with traditional leaching raw materials, the embodiments of the present invention provide high-grade nickel matte as the main material, supplemented by crude nickel hydroxide (MHP) or cobalt hydroxide and nickel-iron powder (NPI) as a wide range of nickel supply sources, avoiding excessive reliance on a single supply source, and the combination of multiple materials better reduces the risk and cost of purchasing raw materials.

[0089] This invention also provides a method for preparing a cathode material precursor, comprising using the leachate obtained by the leaching method provided in this invention as a raw material, and preparing the cathode material precursor by co-precipitation. Since the preparation cost of the leachate is low, it helps to reduce the preparation cost of the cathode material precursor; the leachate provided in this invention has a low impurity content, which can improve the purity of the precursor product and thus improve the electrochemical performance of the cathode material.

[0090] Specifically, the qualified wet process solution obtained by the method of the present invention is used to synthesize a ternary precursor (nickel-cobalt-manganese hydroxide) by adding cobalt and manganese sources and adjusting the ratio, thereby providing a new source of raw materials for high-nickel ternary precursors.

[0091] In actual operation, metal salts can be added to the leachate according to the chemical formula of the target precursor, the proportion of elements such as nickel, cobalt and manganese can be adjusted, and complexing agents and precipitants can be added during the co-precipitation reaction to promote the co-precipitation reaction and obtain a precursor product with uniform particle size.

[0092] This invention also provides a cathode material precursor, which is prepared by the above-described preparation method and has the advantages of low preparation cost and high product purity.

[0093] This invention also provides a cathode material, which is prepared from the cathode material precursor provided in this invention, and also has the advantages of low preparation cost and high product purity.

[0094] This invention also provides a positive electrode sheet, including the above-mentioned positive electrode material, and may further include a positive electrode current collector. A positive electrode active coating is formed on at least one surface of the positive electrode current collector. The positive electrode material provided in this invention exists as a positive electrode active material in the positive electrode active coating.

[0095] This invention provides a secondary battery, including the above-mentioned positive electrode, and may also include a negative electrode, electrolyte, separator, etc. to form a complete battery structure with good cycle performance.

[0096] In other embodiments, it may not be in the form of a secondary battery, but may be in the form of a battery module, battery pack, etc.

[0097] This invention provides a device comprising the aforementioned secondary battery, battery module, or battery pack. The secondary battery, battery module, or battery pack can serve as a power source for the device or as an energy storage unit. This device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0098] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0099] Example 1

[0100] This embodiment provides a leaching method for high-grade nickel matte, including the following specific steps:

[0101] (1) The composition of the provided high-grade nickel matte by mass fraction is as follows: nickel content 47.92%, Co content 1.19%, Mn content 0.0187%, Cu content 13.81%, Ca content 0.6054%, and Fe content 9%. The high-grade nickel matte is first coarsely crushed and then pulverized into 100-400 mesh powder by a conical ball mill. After the first magnetic separation, nickel-iron elemental powder and the processed high-grade nickel matte powder are obtained.

[0102] (2) The high-grade nickel matte powder obtained after the first magnetic separation is mixed with potassium permanganate at a ratio of 1:2, and calcium carbonate buffer is added at 3% of the total weight (i.e., the mass ratio of calcium carbonate buffer to the total amount of high-grade nickel matte powder and potassium permanganate is 3:100). The mixture is prepared in alumina trough crucible and ignited in an air atmosphere for a self-heating reaction (ignition temperature of about 150°C). The reaction process continues until the potassium permanganate or high-grade nickel matte material is completely burned. The powder after the reaction is then subjected to a second magnetic separation to remove iron.

[0103] (3) After the secondary magnetic separation to remove iron, the material (i.e., the pre-treated powder) is subjected to a low-acid leaching. The specific steps are as follows: the pre-treated powder is placed in a crucible, and tap water is sprayed at a solid-liquid mass ratio of 1:3. The slurry is introduced into the corresponding reaction tank, and tap water is added to the reaction tank as the bottom water. The reaction vessel is a normal pressure steel-lined acid-resistant brick reaction tank. 98% concentrated sulfuric acid is slowly added. The mass ratio of pre-treated powder to concentrated sulfuric acid is 1:1.2. The pH is adjusted to 0.5-1.0. After stabilizing for 1 hour, crude nickel hydroxide (MHP, purchased from GEM Co., Ltd.) is added to adjust the pH value to 2.0-2.5. The reaction is carried out for 2 hours. The reaction temperature of the entire leaching process is 70℃. The nickel, cobalt and manganese in the leaching solution and leaching residue are detected to obtain qualified low-acid leaching slurry.

[0104] (4) Adjust the temperature of the qualified low-acid leaching slurry after the reaction in step (3) to 85°C, and filter it through a diaphragm filter press to separate the low-acid leaching residue and low-acid leaching liquid.

[0105] The low-acid leaching residue is mixed with 98% concentrated sulfuric acid, and the pH is adjusted to 0.5-1.0. After adjusting the temperature to 60°C, it is mixed with 20% hydrogen peroxide solution for reaction. After the pH increases, concentrated sulfuric acid is added again for adjustment. The addition of sulfuric acid and reducing agent is repeated several times to keep the pH at 0.5-1.0 for secondary low-acid leaching. After the secondary low-acid leaching reaction is completed, the mixture is filtered to obtain secondary low-acid leaching solution and secondary low-acid leaching residue. The secondary low-acid leaching solution is returned to the primary low-acid leaching stage and mixed with the pretreated powder to make a pulp.

[0106] After a chemical impurity removal process, nickel-iron powder with a particle size of 100-150 mesh is slowly added to the low-acid leaching solution at a ratio of 1:1 to remove copper once (the molar ratio of the total amount of nickel-iron to the copper content in the low-acid leaching solution is 1:1). The reaction is carried out for 2 hours, and sulfuric acid is added to adjust the pH value to 0.5-1.0. The solution is stabilized under stirring for 2 hours and then allowed to stand for 4 hours before being transferred to an aging storage tank to enter the next process.

[0107] (5) The copper-removed liquid obtained in step (4) is heated to 90℃ and MHP (crude nickel hydroxide, purchased from GEM Co., Ltd.) is added to adjust the pH to 2.0-2.5. After stabilizing for 2 hours, hydrogen peroxide with a mass fraction of 8% is added to oxidize the ferrous iron according to the remaining ferrous iron content. The temperature is controlled between 80℃ and 95℃, and soda ash solution is added to adjust the pH to 3.8 to 4.2 to remove iron and aluminum. After stabilizing for 1 hour, after solid-liquid separation, the obtained wet process liquid is further extracted to remove calcium, magnesium, zinc and copper to obtain a qualified wet process liquid. The specific operation steps for extracting calcium, magnesium, zinc and copper are as follows (the same below): the wet process liquid is extracted with P204 to remove calcium, zinc and copper to obtain manganese sulfate solution (obtained by organic reverse extraction), the first stage raffinate is extracted with P507 to separate cobalt to obtain cobalt sulfate solution, the second stage raffinate is extracted with C272 to separate magnesium, and the third stage raffinate is extracted with P507 to separate nickel to obtain nickel sulfate solution. The three are mixed to form the required nickel cobalt manganese sulfate solution.

[0108] (6) A 10% ammonia solution, a 30% sodium hydroxide solution, and water are added to the reactor as the base liquid, with the ammonia concentration controlled at 10% and the pH value at 8. Nickel sulfate, cobalt sulfate, and manganese sulfate are added to the prepared qualified wet process solution at a molar ratio of 8:1:1 to prepare a nickel-cobalt-manganese mixed solution with a total concentration of 100 g / L. The nickel-cobalt-manganese mixed solution, ammonia solution, and sodium hydroxide solution are added to the reactor, and nitrogen is introduced as a protective gas. The pH in the reactor is adjusted to 10, the ammonia concentration to 10%, the temperature to 50℃-60℃, and the stirring speed to 150 r / min. A nucleation reaction is carried out in the reactor (the residence time is controlled by a nucleus generator so that the reaction only generates nuclei and does not grow), resulting in a slurry. The design incorporates a series overflow process to allow the prepared slurry to overflow into the growth vessel, enabling the nuclei of the ternary precursor to grow without generating new nuclei. The slurry from the growth vessel is then overflowed into the synthesis vessel (the reactor used in the synthesis process), where precipitation, washing, separation, and drying are performed to obtain the 8-series ternary precursor.

[0109] Example 2

[0110] This embodiment provides a leaching method for high-grade nickel matte, including the following specific steps:

[0111] (1) The composition of the provided high-grade nickel matte is as follows by mass fraction: nickel content is 47.92%, Co content is 1.19%, Mn content is 0.0187%, Cu content is 13.81%, Ca content is 0.6054%, and Fe content is 9%. The high-grade nickel matte is first coarsely crushed and then pulverized into 100-400 mesh powder by a conical ball mill.

[0112] (2) Mix the ground high-grade nickel matte powder with potassium permanganate at a ratio of 1:2 in an alumina trough crucible according to the quantitative configuration, and ignite the self-heating reaction in an air atmosphere (ignition temperature of about 150°C). The reaction process continues until the potassium permanganate or high-grade nickel matte material is completely burned.

[0113] (3) The material obtained in step (2) is subjected to a low-acid leaching process. The specific steps are as follows: According to the amount of material in the crucible, spray tap water at a solid-liquid mass ratio of 1:3. The slurry is introduced into the corresponding reaction tank. Tap water is added to the reaction tank as the bottom water. The reaction vessel is a normal pressure steel-lined acid-resistant brick reaction tank. Slowly add concentrated sulfuric acid with a mass fraction of 98%. The mass ratio of pretreatment powder to concentrated sulfuric acid is 1:1.2. Adjust the pH to 0.5-1.0. After stabilizing for 1 hour, add cobalt hydroxide to adjust the pH to 2.0-2.5. React for 2 hours. The reaction temperature of the entire leaching process is 70℃. Detect nickel, cobalt and manganese in the leaching solution and leaching residue to obtain qualified low-acid leaching slurry.

[0114] (4) Adjust the temperature of the qualified low-acid leaching slurry after the reaction in step (3) to 85°C, and filter it through a diaphragm filter press to separate the low-acid leaching residue and low-acid leaching liquid.

[0115] The low-acid leaching residue undergoes a secondary low-acid leaching process: the low-acid leaching residue is mixed with 98% concentrated sulfuric acid, the pH is adjusted to 0.5-1.0, and the temperature is adjusted to 60℃ before being mixed with 20% hydrogen peroxide solution for reaction. As the pH rises, concentrated sulfuric acid is added again for adjustment. This process of adding sulfuric acid and reducing agent is repeated multiple times until the pH reaches 0.5-1.0, resulting in a secondary low-acid leaching. After the secondary low-acid leaching reaction is complete, the residue is filtered to obtain a secondary low-acid leaching solution and a secondary low-acid leaching residue. The secondary low-acid leaching solution is returned to the primary low-acid leaching stage and mixed with the pre-treated powder to form a slurry.

[0116] After a chemical impurity removal process, nickel-iron powder with a particle size of 100-150 mesh is slowly added to the low-acid leaching solution at a ratio of 1:1 to remove copper once (the molar ratio of the total amount of nickel-iron to the copper content in the low-acid leaching solution is 1:1). The reaction is carried out for 2 hours, and sulfuric acid is added to adjust the pH value to 0.5-1.0. The solution is stabilized under stirring for 2 hours and then allowed to stand for 4 hours before being transferred to an aging storage tank to enter the next process.

[0117] (5) According to step (4), the copper-removed liquid is heated to 90℃ and MHP (crude nickel hydroxide, purchased from GEM Co., Ltd.) is added to adjust the pH to 2.0-2.5. After stabilizing for 2 hours, hydrogen peroxide with a mass fraction of 8% is added to oxidize the ferrous iron according to the remaining ferrous iron content. The temperature is controlled at 80℃ to 95℃. Soda ash solution is added to adjust the pH value to 3.8 to 4.2 to remove iron and aluminum. After stabilizing for 1 hour, after solid-liquid separation, the obtained wet process liquid is further extracted to remove calcium, magnesium, zinc and copper to obtain a qualified wet process liquid. The specific operation steps for extracting calcium, magnesium, zinc and copper are as follows (the same below): the wet process liquid is extracted with P204 to remove calcium, zinc and copper to obtain manganese sulfate solution (obtained by organic reverse extraction). The first stage raffinate is extracted with P507 to separate cobalt to obtain cobalt sulfate solution. The second stage raffinate is extracted with C272 to separate magnesium. The third stage raffinate is extracted with P507 to separate nickel to obtain nickel sulfate solution. The three are mixed to form the required nickel cobalt manganese sulfate solution.

[0118] (6) The specific steps are the same as in Example 1.

[0119] Example 3

[0120] The only difference from Example 2 is that in step (4), nickel-iron powder is replaced with iron powder, and the molar ratio of iron to copper is controlled to be 1:1.

[0121] Example 4

[0122] The only difference from Example 1 is that the pre-treated material is not subjected to magnetic separation to remove iron (i.e., no primary or secondary magnetic separation is performed).

[0123] Example 5

[0124] The only difference from Example 1 is that iron powder is used in the copper removal process.

[0125] Comparative Example 1

[0126] The only difference from Example 1 is that no oxidant is added in the pretreatment process, and the sample is calcined at 1000°C in an oxygen atmosphere for 4 hours, followed by low-acid leaching.

[0127] Comparative Example 2

[0128] The only difference from Example 1 is that the high-grade nickel matte does not undergo a pretreatment process (i.e., steps (1) and (2) are not performed), and is directly leached with low acid.

[0129] Comparative Example 3

[0130] This comparative example provides a traditional high-grade nickel matte leaching process, with the following specific steps:

[0131] (1) The composition of the provided high-grade nickel matte by mass fraction is as follows: nickel content 47.92%, Co content 1.19%, Mn content 0.0187%, Cu content 13.81%, Ca content 0.6054%, and Fe content 9%. The high-grade nickel matte is first coarsely crushed and then pulverized into 60-200 mesh powder by a conical ball mill. The powder is mixed with lithium manganese oxide electrode powder at a mass ratio of 1:1. The mixture is then roasted in a rotary kiln at a temperature of 200°C for 60 minutes. After the first roasting, the material is roasted in a second roasting at a temperature of 400°C. Water is sprayed once at 90 minutes of roasting, with the water volume controlled at 5% of the total weight of the material. The roasting time is 180 minutes, and the protective atmosphere is air. After cooling, the pretreated powder of high-grade nickel matte is obtained.

[0132] (2) The pretreated high nickel matte pretreatment powder is mixed with cathode material powder at a mass ratio of 1:2, concentrated water is added as bottom water, and slurry is prepared at a solid-liquid ratio of 1:3 (other ratios are also acceptable, but the leaching rate will be slightly different). The reaction vessel is a normal pressure steel-lined acid-resistant brick reaction tank. Sulfuric acid is added to repeatedly adjust the pH to 0.5-1.0. Unqualified ternary precursor is added to adjust the pH to 2.0-2.5. 50 kg of filter aid is added, and the temperature is raised to 80℃ to obtain low acid leaching slurry.

[0133] (3) The above reaction solution was filtered through a diaphragm filter press with a filtration efficiency of 20 m³ / s. 3 / h, low-acid leaching residue and low-acid leaching solution are separated. The low-acid leaching residue undergoes a normal pressure high-acid leaching process. The high-acid leaching solution is returned to the normal pressure low-acid leaching step and mixed with pretreatment powder to form a pulp. The low-acid leaching solution undergoes a chemical impurity removal process, with iron powder added to remove copper once, 8% hydrogen peroxide to oxidize ferrous iron, and the temperature controlled at 80℃ to 95℃. Unqualified precursors are added to adjust the pH to 3.0 to 3.5, and then soda ash solution is added to adjust the pH to 3.8 to 4.2 to remove iron and aluminum. After solid-liquid separation, the obtained wet process solution is further subjected to extraction to remove calcium, magnesium and zinc, and raffinate to remove lithium, to obtain a qualified wet process solution.

[0134] (4) Mix 1 / 3 of sodium borohydride with a mass concentration of 0.5wt%, 1 / 3 of ammonia with a mass concentration of 6wt%, water and sodium hydroxide, and add them to the reactor as the base liquid. Add cobalt sulfate and manganese sulfate to the qualified wet process liquid to prepare a nickel-cobalt-manganese mixed solution with a nickel-cobalt-manganese molar ratio of 6:2:2 and a total nickel-cobalt-manganese concentration of 100g / L. Mix the solution with the remaining ammonia and sodium borohydride and add it to the reactor. Then, introduce nitrogen gas as a protective gas.

[0135] (5) Adjust the pH in the reactor to 10.1, the temperature to 50℃-60℃, and the stirring speed to 250r / min. Carry out the nucleation reaction in the reactor (control the residence time through the nucleus generator so that the reaction only generates nuclei and does not grow) to obtain a slurry. Design and configure the overflow program of the reactor series to overflow the obtained slurry to the growth reactor, so that the nuclei of the ternary precursor can grow without generating new nuclei. Overflow the slurry of the growth reactor to the synthesis reactor (the reactor used in the synthesis process). After precipitation, washing, separation and drying, the 6-series ternary precursor is obtained.

[0136] Experimental Example 1

[0137] The leaching effects of the above embodiments and comparative leaching methods were tested, and the results are shown in Table 1.

[0138] Test method:

[0139] (1) Low acid leaching nickel leaching rate: atomic absorption spectrometry;

[0140] (2) Copper removal effect: Atomic absorption spectrometry.

[0141] Table 1. Leaching effects of the leaching methods in the examples and comparative examples.

[0142] Low acid leaching nickel leaching rate Low acid reaction time (h) Copper removal effect Copper removal reaction time (h) Example 1 95.4％ 3 97.4％ 2 Example 2 95.1％ 3 95.8％ 2 Example 3 94.5％ 3 94.9％ 2 Example 4 95.2％ 3 97.2％ 2 Example 5 95.3％ 3 96.5％ 2 Comparative Example 1 72.5％ 12 95.7％ 2 Comparative Example 2 30.2％ 12 96.1％ 2 Comparative Example 3 75.5％ 8 95.2％ 2

[0143] It can be seen that the leaching method provided in the embodiments of the present invention has a high leaching rate, a short low-acid leaching time, and a relatively ideal copper removal effect.

[0144] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A leaching method for high-grade nickel matte, characterized in that, include: Raw material pretreatment: High-grade nickel matte is mixed with an oxidant and subjected to an ignition-based autothermal reaction; One-time low-acid leaching: The powder obtained from the pretreatment of the raw materials is subjected to one-time low-acid leaching under non-pressurized conditions, and the pH value of the leaching is controlled to be 0.5-1.0; The oxidant is selected from at least one of potassium permanganate and sodium permanganate.

2. The leaching method according to claim 1, characterized in that, The raw material pretreatment process includes: performing a first magnetic separation on high-grade nickel matte to obtain nickel-iron element and high-grade nickel matte powder; mixing the high-grade nickel matte powder with an oxidant and a buffer to carry out an autothermal reaction to obtain intermediate pretreatment powder; and performing a second magnetic separation on the intermediate pretreatment powder to obtain pretreatment powder. During the raw material pretreatment process, at least one of features A1-A6 is satisfied: Feature A1: The high-grade nickel matte is first pulverized to a particle size of 100-400 mesh, and then subjected to the first magnetic separation. Feature A2: The mass ratio of the high-grade nickel matte powder to the oxidant is 1:(1-3); Feature A3: The buffer is selected from at least one of calcium carbonate and calcium hydroxide; Feature A4: The mass ratio of the buffer to the total amount of the high-grade nickel matte powder and the oxidant is (1-10):100; Feature A5: The reaction time of the self-heating reaction is 50 min-120 min; Feature A6: The self-heating reaction is carried out in an air atmosphere.

3. The leaching method according to claim 2, characterized in that, The process of the first low-acid leaching includes: leaching the pretreated powder in a sulfuric acid solution; After reacting for 1-2 hours, the first solid-liquid separation is performed; Alternatively, after reacting for 1-2 hours, add pre-treated powder to adjust the pH value to 2.0-2.5, react for 2-3 hours, and then perform the first solid-liquid separation. Alternatively, after reacting for 0.5-2.0 hours, crude nickel hydroxide or crude cobalt hydroxide can be added to adjust the pH to 2.0-2.5, react for 2-3 hours, and then perform the first solid-liquid separation.

4. The leaching method according to claim 3, characterized in that, The pretreated powder is mixed with water and concentrated sulfuric acid, and the resulting slurry is reacted under conditions with a pH of 0.5-1.

0. During the single low-acid leaching process, at least one of the following characteristics B1-B5 is satisfied: Feature B1: The mass ratio of the pretreatment powder to water is 1:(1-4); Feature B2: The mass ratio of the pretreatment powder to concentrated sulfuric acid is 1:(1.0-1.5), and the mass fraction of the concentrated sulfuric acid is greater than or equal to 98%; Feature B3: The reaction temperature for the first low-acid leaching is 50℃-90℃; Feature B4: Before the first solid-liquid separation, the temperature of the material after the reaction is completed is adjusted to 80℃-90℃; Feature B5: The first solid-liquid separation is carried out in a diaphragm filter press.

5. The leaching method according to claim 3, characterized in that, Also includes: The first low-acid leaching residue obtained from the first solid-liquid separation is mixed with sulfuric acid to adjust the pH value to 0.5-1.

0. After adjusting the temperature to 50℃-70℃, it is mixed with a reducing agent and reacted. Sulfuric acid and the reducing agent are repeatedly added to adjust the pH value to 0.5-1.0 for a second low-acid leaching.

6. The leaching method according to claim 5, characterized in that, After the secondary low-acid leaching reaction is completed, a second solid-liquid separation is performed to obtain secondary low-acid leaching solution and secondary low-acid leaching residue; the secondary low-acid leaching solution is returned to the primary low-acid leaching stage and mixed with the pre-treated powder to form a pulp.

7. The leaching method according to claim 5, characterized in that, The reducing agent is a hydrogen peroxide solution with a mass fraction of 8%-30%.

8. The leaching method according to claim 3, characterized in that, The first low-acid leachate obtained from the first solid-liquid separation is subjected to copper removal, ferrous removal, and iron-aluminum removal in sequence to obtain a purified leachate.

9. The leaching method according to claim 8, characterized in that, The copper removal process includes: mixing the primary low-acid leaching solution with the nickel-iron element or nickel-iron powder and reacting for 1-2 hours, then adding sulfuric acid to adjust the pH value to 0.5-1.0, and letting it stand for 2-4 hours to obtain the copper-removed solution.

10. The leaching method according to claim 9, characterized in that, Before allowing it to stand for 2-4 hours, allow the pH value to stabilize for 1-4 hours under stirring conditions.

11. The leaching method according to claim 9, characterized in that, By adjusting the amount of nickel-iron element or nickel-iron powder added, the molar ratio of the total amount of nickel-iron added to the copper ions in the primary low-acid leaching solution is 1:(0.5-1.5).

12. The leaching method according to claim 11, characterized in that, The particle size of the nickel-iron powder is 60-200 mesh.

13. The leaching method according to claim 9, characterized in that, The solution after the first copper removal is mixed with hydrogen peroxide solution to remove ferrous iron. The temperature is raised to 80℃-95℃ and the pH is adjusted to 3.8-4.5 to further remove iron and aluminum. Then, calcium, magnesium, zinc and copper are removed by extraction.

14. The leaching method according to claim 13, characterized in that, The process of removing ferrous ions includes: heating the solution after the first copper removal to 80℃-95℃, adding crude nickel hydroxide to adjust the pH to 2.0-3.0, and adding hydrogen peroxide solution with a mass fraction of 8%-30% to remove the remaining ferrous ions.

15. The leaching method according to claim 13, characterized in that, The pH value can be adjusted to 3.8-4.5 by adding sodium carbonate solution.

16. A method for preparing a cathode material precursor, characterized in that, The method includes using the leachate obtained by any one of the leaching methods described in claims 1-15 as raw material to prepare the cathode material precursor by co-precipitation.

17. The preparation method according to claim 16, characterized in that, Metal salts are added to the leachate, and complexing agents and precipitants are added during the co-precipitation reaction.

18. A cathode material precursor, characterized in that, It is prepared by the preparation method described in claim 16 or 17.

19. A positive electrode material, characterized in that, It is prepared using the cathode material precursor described in claim 18.

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