Preparation method of positive electrode material precursor and application thereof

Abstract

The application provides a preparation method of a positive electrode material precursor and application thereof. The preparation method of the positive electrode material precursor comprises the following steps: performing phosphating treatment on waste nickel-cobalt-manganese lithium acid cathode material, so that metal elements in the waste nickel-cobalt-manganese lithium acid cathode material are converted into phosphate to prepare a phosphate mixed phase; heating the phosphate mixed phase under a reducing atmosphere to perform reduction treatment, so that a positive electrode material precursor mixed phase is obtained; and performing phase separation on the positive electrode material precursor mixed phase through physical sorting, so that a positive electrode material precursor is obtained. The preparation method of the positive electrode material precursor provided by the application can realize efficient separation of valuable metals in waste NCM cathode material and directly obtain a precursor product that can be used for positive electrode material regeneration, under the premise of avoiding introduction of water phase treatment.

Description

Technical Field

[0001] This application relates to the field of battery recycling technology, specifically to a method for preparing a cathode material precursor and its application. Background Technology

[0002] The recycling of cathode materials from spent lithium-ion batteries is a crucial aspect of the sustainable development of the new energy industry. Among these, lithium nickel cobalt manganese oxide (LCO) ternary cathode materials have attracted significant attention due to their rich content of valuable metals such as nickel, cobalt, manganese, and lithium. Currently, the recycling of LCO ternary batteries primarily relies on a wet acid leaching process. This process involves leaching valuable metals from the cathode material using an acid solution, followed by multi-stage extraction and precipitation steps to achieve metal separation. However, this method suffers from inherent drawbacks such as a lengthy process, high consumption of chemical reagents, and difficulties in treating high-salt wastewater.

[0003] To address the aforementioned shortcomings, related technologies employ pyrometallurgical or semi-pyrometallurgical recovery routes. These routes utilize reducing gases such as hydrogen at high temperatures to reduce metal oxides in the cathode material into elemental metals or low-valence compounds, followed by subsequent processing to separate and recover the metals. Compared to hydrometallurgical processes, the pyrometallurgical route is simpler and requires less chemical reagents. However, traditional pyrometallurgical routes suffer from high energy consumption during the high-temperature reduction process, demanding equipment requirements. They also typically require wet processes such as water immersion to separate and extract specific elements like lithium, failing to fundamentally overcome the wastewater discharge problem. Furthermore, traditional pyrometallurgical routes rely on limited methods for separating reduction products, usually only using magnetic separation to roughly distinguish between magnetic and non-magnetic components. This makes it difficult to achieve precise separation of multiple components, resulting in the mixing of valuable elements such as nickel, cobalt, manganese, and lithium in the products, limiting the high-value utilization of the recovered products.

[0004] Therefore, how to achieve efficient separation of valuable metals from waste NCM cathode materials and obtain precursor products that can be used for cathode material regeneration while reducing wastewater discharge is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, this application provides a method for preparing a cathode material precursor and its application. This application improves the process flow for preparing cathode material precursors by recycling waste cathode materials. By using a combination of phosphorylation treatment, reduction treatment and physical sorting, the cathode material precursor phases can be fully separated. Moreover, the entire process does not require the introduction of wet treatment steps such as water immersion, which can effectively reduce wastewater discharge.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for preparing a cathode material precursor, comprising the following steps: mixing waste lithium nickel cobalt manganese oxide cathode material with a phosphate source, and then subjecting the mixture to heat treatment to convert the metal elements in the waste lithium nickel cobalt manganese oxide cathode material into phosphates, thereby preparing a phosphate mixed phase; heating the phosphate mixed phase under a reducing atmosphere for reduction treatment to obtain a cathode material precursor mixed phase; and separating the cathode material precursor mixed phase by physical sorting to obtain the cathode material precursor.

[0007] Based on the first aspect, in some embodiments, the mass ratio of waste nickel cobalt manganese oxide cathode material to phosphoric acid source is 1:(0.3~0.8).

[0008] Based on the first aspect, in some embodiments, the phosphoric acid source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium polyphosphate.

[0009] Based on the first aspect, in some embodiments, the heat treatment temperature is 300°C to 400°C.

[0010] Based on the first aspect, in some embodiments, the heat treatment time is 1 h to 2 h.

[0011] Based on the first aspect, in some embodiments, the temperature of the phosphate mixed phase is ≤530°C when it is heated in a reducing atmosphere for reduction treatment.

[0012] Based on the first aspect, in some embodiments, heating the phosphate mixed phase under a reducing atmosphere for reduction treatment includes the following steps: heating to a first temperature and holding it at a first reducing atmosphere, and heating from the first temperature to a second temperature and holding it at a second reducing atmosphere.

[0013] Based on the first aspect, in some implementations, the second temperature is higher than the first temperature.

[0014] Based on the first aspect, in some embodiments, the content of reducing gas in the second reducing atmosphere is higher than the content of reducing gas in the first reducing atmosphere.

[0015] Based on the first aspect, in some embodiments, the holding time at the second temperature is longer than the holding time at the first temperature.

[0016] Based on the first aspect, in some embodiments, the first reducing atmosphere comprises H2 at a volume percentage of 2% to 5%.

[0017] Based on the first aspect, in some embodiments, the first temperature is 400℃~450℃, and the holding time is 1 h~2 h.

[0018] Based on the first aspect, in some embodiments, the second reducing atmosphere comprises H2 at a volume percentage of 5% to 10%.

[0019] Based on the first aspect, in some embodiments, the second temperature is 480℃~530℃, and the holding time is 2 h~4 h.

[0020] Based on the first aspect, in some embodiments, physical sorting includes at least one of magnetic separation, airflow classification, and electrostatic separation.

[0021] Based on the first aspect, in some implementations, the magnetic field strength of the magnetic separation is 0.1 T to 0.3 T.

[0022] Based on the first aspect, in some implementations, the airflow velocity for airflow grading is 2 m / s to 5 m / s.

[0023] Based on the first aspect, in some implementations, the voltage for electrostatic separation is 15 kV to 30 kV.

[0024] Based on the first aspect, in some embodiments, the cathode material precursor includes one or more of the following independent phases: i) Ni2P / Co2P composite phase; ii) Li3PO4 phase; iii) Mn3(PO4)2 phase.

[0025] Based on the first aspect, in some embodiments, the Ni and Co grades in the Ni2P / Co2P composite phase are ≥93%.

[0026] Based on the first aspect, in some embodiments, the purity of Li3PO4 in the Li3PO4 phase is ≥88%.

[0027] Based on the first aspect, in some embodiments, the purity of Mn3(PO4)2 in the Mn3(PO4)2 phase is ≥85%.

[0028] Secondly, this application provides the application of the above-mentioned preparation method in the preparation of at least one of the following functional materials: i) NCM ternary precursor; ii) lithium supplement for cathode materials; iii) lithium iron manganese phosphate cathode materials.

[0029] Compared to traditional technologies, the beneficial effects of this application are as follows:

[0030] The method for preparing cathode material precursors provided in this application releases four metal elements from the original oxide lattice through phosphorylation, allowing them to recombine in the form of their respective phosphates. Utilizing the differences in chemical stability and response to reducing atmospheres among Ni3(PO4)2, Co3(PO4)2, Mn3(PO4)2, and Li3PO4, a material basis is provided for subsequent differentiated conversion through reduction treatment. Based on this, the phosphate mixture is heated under a reducing atmosphere, causing the different phosphate components to undergo differentiated reduction conversions according to their own thermodynamic properties. This results in a cathode material precursor mixture containing multiple phases with different physical properties obtained in the same reduction process. By utilizing the differences in magnetic properties, density, and conductivity among these phases, the mixture can be physically separated into multiple single phases, yielding precursor products that can be directly used for cathode material regeneration.

[0031] The method for preparing cathode material precursors provided in this application eliminates the need for wet treatment processes such as water immersion, thus mitigating the risk of generating high-salt wastewater. Furthermore, the simplified process reduces energy and reagent consumption during recycling. Therefore, the method for preparing cathode material precursors provided in this application enables the efficient separation of valuable metals from waste NCM cathode materials and the direct acquisition of precursor products suitable for cathode material regeneration, without the need for aqueous phase treatment. Detailed Implementation

[0032] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions will be provided below. The technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the technical solutions of this application more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] One embodiment of this application provides a method for preparing a cathode material precursor, comprising the following steps:

[0035] Step 1: Mix waste lithium nickel cobalt manganese oxide cathode material with phosphate source, and then perform heat treatment to convert the metal elements in the waste lithium nickel cobalt manganese oxide cathode material into phosphate, thus preparing a phosphate mixed phase.

[0036] In related technologies, in waste NCM cathode materials, nickel, cobalt, manganese, and lithium coexist in the same crystal lattice as layered oxides, with similar chemical bonding states, making it difficult to effectively distinguish them directly through physical means or conventional reduction. In the aforementioned steps, phosphorylation treatment of the waste lithium nickel cobalt manganese oxide cathode material converts the original layered oxides of nickel, cobalt, manganese, and lithium into phosphates, forming a homogeneous phosphate mixture phase. This phosphorylation treatment releases the four metal elements from the original oxide lattice, allowing them to recombine in their respective phosphate forms. Utilizing the differences in chemical stability and response to reducing atmospheres among Ni3(PO4)2, Co3(PO4)2, Mn3(PO4)2, and Li3PO4 provides a material basis for subsequent differentiated conversion through reduction treatment. Furthermore, in this application, the phosphorylation treatment is achieved by mixing the waste lithium nickel cobalt manganese oxide cathode material with a phosphoric acid source followed by heat treatment. This application employs a solid-phase reaction method involving heat treatment after mixing. This allows the phosphate source to fully contact and react with the NCM particles during heating, ensuring that the layered oxide structure in the NCM is fully penetrated and destroyed by phosphate ions, thereby achieving complete conversion of metal elements into phosphates. Compared to phosphate treatment methods performed in solution systems, this solid-phase heat treatment route eliminates the need for subsequent liquid-solid separation operations, simplifying the process and reducing wastewater generation.

[0037] In some embodiments, the mass ratio of waste lithium nickel cobalt manganese oxide cathode material to phosphoric acid source is 1:(0.3~0.8). For example, the mass ratio of waste lithium nickel cobalt manganese oxide cathode material to phosphoric acid source can be 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, or any value within the range of any two of the above values. Furthermore, controlling the mass ratio of waste lithium nickel cobalt manganese oxide cathode material to phosphoric acid source within the above range during phosphorylation treatment helps to provide sufficient phosphate ions to achieve complete phosphorylation of the metal elements, while avoiding excessive phosphoric acid source residue in the product.

[0038] In some embodiments, the phosphoric acid source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium polyphosphate. Furthermore, when the phosphoric acid source is selected from the above substances, the ammonium salt phosphoric acid source releases phosphate ions during heating and decomposes to produce gaseous products, which helps to reduce the introduction of impurity elements.

[0039] In some embodiments, the heat treatment temperature is 300°C to 400°C. For example, the heat treatment temperature can be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, or any value within the range of any two of the above values. Furthermore, controlling the heat treatment temperature within the above range during phosphorylation provides sufficient energy to break the layered structure of NCM and drive the phosphorylation reaction, while also preventing excessive sintering of phosphates or abnormal grain growth due to excessively high temperatures.

[0040] In some embodiments, the heat treatment time is 1 h to 2 h. For example, the heat treatment time can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, or any value within the range of any two of the above values. Furthermore, controlling the heat treatment time during phosphorylation within the above range helps to ensure that the phosphorylation reaction proceeds fully, while also helping to avoid grain coarsening and increased energy consumption caused by excessively long treatment times.

[0041] Step 2: The phosphate mixed phase is heated under a reducing atmosphere to undergo reduction treatment, thereby obtaining the cathode material precursor mixed phase.

[0042] In the above steps, the phosphate mixed phase is heated under a reducing atmosphere, so that different phosphate components undergo differentiated reduction transformations according to their own thermodynamic properties, thereby obtaining a cathode material precursor mixed phase containing multiple phases with different physical properties in the same reduction process.

[0043] In some embodiments, the phosphate mixed phase is heated under a reducing atmosphere for reduction treatment at a temperature ≤530°C. Further, this application has found that at ≤530°C, the reduction reaction of Mn3(PO4)2 is difficult to proceed spontaneously, thus maintaining its weakly paramagnetic phosphate phase state; while Ni3(PO4)2 and Co3(PO4)2 can be reduced to ferromagnetic Ni2P / Co2P at this temperature. By controlling the temperature to not exceed 530°C during the reduction treatment, it is helpful to prevent Mn reduction while Ni and Co are fully reduced, thereby creating an order-of-magnitude difference in magnetic properties between Ni / Co and Mn / Li. This upper temperature limit helps prevent Mn from entering the magnetic product phase, creating the necessary phase conditions for subsequent physical sorting to obtain pure Mn3(PO4)2 and Ni2P / Co2P phases. Simultaneously, controlling the above temperature threshold also helps reduce high-temperature energy consumption and lower production costs.

[0044] In some embodiments, the phosphate mixed phase is heated under a reducing atmosphere for reduction treatment, comprising the following steps: heating to a first temperature and holding at that temperature under a first reducing atmosphere, and heating from the first temperature to a second temperature and holding at that temperature under a second reducing atmosphere. In some embodiments, the second temperature is higher than the first temperature. In some embodiments, the content of reducing gas in the second reducing atmosphere is higher than the content of reducing gas in the first reducing atmosphere. In some embodiments, the holding time at the second temperature is longer than the holding time at the first temperature. Further, the reduction treatment employs a two-stage heating program, and when at least one of the H2 content, temperature, and holding time of the reducing atmosphere in the first and second heating programs meets the above conditions, the Ni / Co phosphate surface can be locally activated and the PO bond weakened during the first induction period, forming a metastable precursor with high reactivity, which helps overcome the reduction kinetic barrier of Ni / Co phosphate at low temperatures. Then, during the second main reduction period, the activated precursor is fully converted into Ni2P / Co2P, which helps ensure the complete progress of the reduction reaction.

[0045] In some embodiments, the first reducing atmosphere includes H2 at a volume percentage of 2% to 5%. For example, in the first reducing atmosphere, the volume percentage of H2 can be 2%, 2.3%, 2.6%, 2.9%, 3.2%, 3.5%, 3.8%, 4.1%, 4.4%, 4.7%, 5%, or any value within the range of any two of the above values.

[0046] In some embodiments, the first temperature is 400℃~450℃, and the holding time is 1 h~2 h. For example, the first temperature can be 400℃, 405℃, 410℃, 415℃, 420℃, 425℃, 430℃, 435℃, 440℃, 445℃, 450℃, or any value within the range of any two of the above values; the holding time for the first temperature can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, or any value within the range of any two of the above values.

[0047] In some embodiments, the second reducing atmosphere comprises H2 at a volume percentage of 5% to 10%. For example, in the second reducing atmosphere, the volume percentage of H2 can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any value within the range of any two of the above values.

[0048] In some embodiments, the second temperature is 480℃~530℃, and the holding time is 2 h~4 h. For example, the second temperature can be 480℃, 485℃, 490℃, 495℃, 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, or any value within the range of any two of the above values; the holding time of the second temperature can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, 4 h, or any value within the range of any two of the above values.

[0049] Step 3: The mixed phase of the cathode material precursor is separated by physical sorting to obtain the cathode material precursor.

[0050] In the above steps, by taking advantage of the differences in physical properties such as magnetism, density and conductivity of these phases, the mixed phase can be separated into multiple single phases through physical sorting, and precursor products that can be directly used for the regeneration of cathode materials can be obtained.

[0051] The above preparation method eliminates the need for wet treatment processes such as water immersion, thus mitigating the risk of generating high-salt wastewater. Furthermore, its streamlined process reduces energy and reagent consumption during recycling. Therefore, this method enables the efficient separation of valuable metals from waste NCM cathode materials and the direct acquisition of precursor products suitable for cathode material regeneration, without the need for aqueous phase treatment.

[0052] In some embodiments, physical sorting includes at least one of magnetic separation, air classification, and electrostatic separation. Further, this application utilizes the physical sorting methods described above to separate different phases based on differences in their physical properties of magnetism, density, and conductivity. Specifically, magnetic separation leverages the significant magnetic difference between Ni2P / Co2P (ferromagnetic) and Li3PO4 / Mn3(PO4)2 (non-magnetic / weakly paramagnetic) to achieve a first-stage coarse separation; air classification utilizes the significant magnetic difference between Li3PO4 (approximately 2.54 g / cm³) to achieve a first-stage coarse separation; and air classification leverages the significant magnetic difference between Ni2P / Co2P (ferromagnetic) and Li3PO4 / Mn3(PO4)2 (non-magnetic / weakly paramagnetic). 3 ) and Mn3(PO4)2 (approximately 3.33~3.78 g / cm³) 3 The density difference between the two particles enables a second-stage fine separation; electrostatic separation can utilize the difference in conductivity between metal phosphides (conductors) and residual non-magnetic particles (non-conductors) to perform a third-stage purification of magnetic products.

[0053] In some embodiments, the magnetic field strength for magnetic separation is 0.1 T to 0.3 T. For example, the magnetic field strength for magnetic separation can be 0.1 T, 0.12 T, 0.14 T, 0.16 T, 0.18 T, 0.2 T, 0.22 T, 0.24 T, 0.26 T, 0.28 T, 0.3 T, or any value within the range of any two of the above values. Furthermore, controlling the magnetic field strength within the above range helps to capture strongly magnetic Ni2P / Co2P while avoiding the entrainment of weakly magnetic phases.

[0054] In some embodiments, the airflow velocity for airflow grading is 2 m / s to 5 m / s. For example, the airflow velocity for airflow grading can be 2 m / s, 2.3 m / s, 2.6 m / s, 2.9 m / s, 3.2 m / s, 3.5 m / s, 3.8 m / s, 4.1 m / s, 4.4 m / s, 4.7 m / s, 5 m / s, or any value within the range of any two of the above values. Furthermore, controlling the airflow velocity for airflow grading within the above range helps to match the density difference between Li3PO4 and Mn3(PO4)2 to achieve accurate grading.

[0055] In some embodiments, the electrostatic separation voltage is 15 kV to 30 kV. For example, the electrostatic separation voltage can be 15 kV, 16 kV, 17 kV, 18 kV, 19 kV, 20 kV, 21 kV, 22 kV, 23 kV, 24 kV, 25 kV, 26 kV, 27 kV, 28 kV, 29 kV, 30 kV, or any value within the range of any two of the above values. Furthermore, controlling the electrostatic separation voltage within the above range helps to form sufficient separation force between the conductor and the non-conductor, thereby improving the concentrate grade.

[0056] In some embodiments, the cathode material precursor comprises one or more of the following independent phases: i) Ni2P / Co2P composite phase; ii) Li3PO4 phase; iii) Mn3(PO4)2 phase. Further, the Ni2P / Co2P composite phase exists as phosphides of Ni and Co, and its ferromagnetism originates from the intrinsic properties of the Ni2P and Co2P crystal structures. A higher Ni+Co grade means that the product has a lower amount of non-magnetic impurities, making it directly usable for subsequent acid dissolution and NCM precursor synthesis. The Li3PO4 and Mn3(PO4)2 phases each maintain a single phosphate phase with fewer magnetic metal phosphide impurities, which is beneficial for their use as lithium and manganese / phosphorus sources, respectively.

[0057] In some embodiments, the Ni2P / Co2P composite phase has a Ni and Co purity ≥ 93%. In some embodiments, the Li3PO4 phase has a Li3PO4 purity ≥ 88%. In some embodiments, the Mn3(PO4)2 phase has a Mn3(PO4)2 purity ≥ 85%. Furthermore, the high purity indicators of each phase in the cathode material precursor indicate that the above preparation method, through a combination of phosphorylation, reduction, and physical sorting processes, can achieve sufficient separation of the three phases.

[0058] One embodiment of this application also provides the application of the above preparation method in the preparation of at least one of the following functional materials: i) NCM ternary precursor; ii) lithium supplement for cathode materials; iii) lithium iron manganese phosphate cathode materials.

[0059] In this application, the cathode material precursor prepared based on waste nickel-cobalt-manganese lithium cathode material may contain one or more of the following: Ni2P / Co2P composite phase, Li3PO4 phase, and Mn3(PO4)2 phase. The Ni2P / Co2P composite phase exhibits good solubility in dilute sulfuric acid at room temperature, which facilitates the entry of Ni and Co into the solution in ionic form, while avoiding the introduction of other metal impurities into the NCM precursor synthesis system. The Li3PO4 phase has a purity of not less than 90% and few magnetic metal impurities, making it suitable as a direct lithium source for lithium replenishment and regeneration of the cathode material, avoiding the risk of introducing additional impurities due to insufficient lithium source purity during conventional lithium replenishment processes. The Mn3(PO4)2 phase can simultaneously provide manganese and phosphorus sources, with the molar ratio of Mn to P matching the stoichiometric ratio required for LMFP synthesis in this field. This simplifies the raw material preparation steps in the LMFP synthesis process, enabling the product to be directly used as a precursor for the preparation of LMFP cathode materials.

[0060] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0061] Example 1:

[0062] A cathode material precursor is prepared by the following method:

[0063] Step 1: Place waste NCM523 cathode black powder and ammonium dihydrogen phosphate (NH4H2PO4) in a V-type mixer at a mass ratio of 1:0.5 and mix at 30 r / min for 30 min; load the mixture into an alumina boat and place it in a tube furnace, heat it to 400℃ at 5℃ / min, and keep it at this temperature for 1 h in an air atmosphere for phosphorylation pretreatment.

[0064] Step 2: After the pretreated product is cooled to room temperature in the furnace, a mixture of 2% H2 and 98% Ar (flow rate 100 mL / min) is introduced, and the temperature is increased to 400℃ at 5℃ / min and held for 1.5 h for the first stage of reduction. Then, the temperature is increased to 480℃ at 3℃ / min, and the mixture of 5% H2 and 95% Ar (flow rate 100 mL / min) is switched and held for 3 h for the second stage of reduction. After the reduction is completed, the product is cooled to <50℃ in the furnace under Ar atmosphere (flow rate 50 mL / min).

[0065] Step 3: The reduction product is fed into a roller permanent magnet separator with a magnetic field strength of 0.1 T and a roller speed of 60 r / min, for one separation, collecting both magnetic and non-magnetic products. The non-magnetic product is then fed into an air classifier with an air velocity of 2 m / s and a feed rate of 50 g / min, collecting the light and heavy phases separately. The magnetic product is then fed into a roller electrostatic separator with a voltage of 15 kV and a roller speed of 80 r / min, for two separations, collecting the concentrate product.

[0066] Example 2:

[0067] The difference from Example 1 is that in the first step, waste NCM523 cathode black powder and ammonium dihydrogen phosphate (NH4H2PO4) are heat-treated at 350℃ for 1.5 h for phosphorylation pretreatment at a mass ratio of 1:0.3. In the second step, a mixture of 3% H2 and 97% Ar gas (flow rate 100 mL / min) is introduced, and the temperature is increased to 430℃ at a rate of 5℃ / min and held for 1.5 h for the first stage of reduction; then the temperature is increased to 510℃ at a rate of 3℃ / min, and the mixture of 8% H2 and 92% Ar gas (flow rate 100 mL / min) is switched to a rate of 100 mL / min and held for 3 h for the second stage of reduction. In the third step, during magnetic separation, the magnetic field strength is 0.2 T, the roller speed is 60 r / min, and the separation is performed once; during air classification, the air velocity is 3.5 m / s, and the feed rate is 50 g / min; during electrostatic separation, the voltage is 22 kV, the roller speed is 80 r / min, and the separation is performed twice.

[0068] Example 3:

[0069] The difference from Example 1 is that in the first step, waste NCM523 cathode black powder and ammonium dihydrogen phosphate (NH4H2PO4) are heat-treated at 300℃ for 2 h for phosphorylation pretreatment at a mass ratio of 1:0.8. In the second step, a mixture of 5% H2 and 95% Ar gas (flow rate 100 mL / min) is introduced, and the temperature is increased to 450℃ at a rate of 5℃ / min and held for 2 h for the first stage of reduction; then the temperature is increased to 530℃ at a rate of 3℃ / min, and the mixture of 10% H2 and 90% Ar gas (flow rate 100 mL / min) is switched and held for 4 h for the second stage of reduction. In the third step, during magnetic separation, the magnetic field strength is 0.3 T, the roller speed is 60 r / min, and the separation is performed once; during air classification, the air velocity is 5 m / s, and the feed rate is 50 g / min; during electrostatic separation, the voltage is 30 kV, the roller speed is 80 r / min, and the separation is performed twice.

[0070] Example 4:

[0071] The difference from Example 2 is that in the first step, diammonium hydrogen phosphate ((NH4)2HPO4) is used instead of ammonium dihydrogen phosphate, with a mass ratio of 1:0.5 to NCM black powder.

[0072] Example 5:

[0073] The difference from Example 2 is that in the first step, waste NCM811 cathode black powder is used instead of NCM523, with a mass ratio of 1:0.5 with the phosphoric acid source.

[0074] Example 6:

[0075] The difference from Example 2 is that in the second step, the temperature is directly increased to 510°C at 5°C / min, and a mixture of 8%H2 and 92%Ar gas (flow rate 100 mL / min) is introduced and kept at this temperature for 4.5 h for a one-stage reduction (the total holding time is the same as in Example 2).

[0076] Example 7:

[0077] The difference from Example 2 is that in the second step, the temperature is directly increased to 540°C at 5°C / min, and a mixture of 8%H2 and 92%Ar gas (flow rate 100 mL / min) is introduced and kept at this temperature for 3 h for a one-stage reduction.

[0078] Example 8:

[0079] The difference from Example 2 is that in the second step, the temperature is directly increased to 600°C at 5°C / min, and a mixture of 8%H2 and 92%Ar gas (flow rate 100 mL / min) is introduced and kept at this temperature for 3 hours for a one-stage reduction.

[0080] Example 9:

[0081] The difference from Example 2 is that in the second step, the temperature of the second stage of reduction is adjusted to 540°C.

[0082] Example 10:

[0083] The difference from Example 2 is that in the first step, the temperature of the phosphorylation pretreatment is reduced to 250°C and the treatment time is appropriately extended to 2 hours.

[0084] Example 11:

[0085] The difference from Example 2 is that in the third step, only 0.2T dry magnetic separation (roller speed 60 r / min, 1 separation) is performed, without airflow classification and electrostatic separation.

[0086] Comparative Example 1:

[0087] The difference from Example 2 is that the second step is omitted, and the product after the first step of phosphorylation pretreatment is cooled and directly subjected to the third step of three-stage physical sorting.

[0088] Comparative Example 2:

[0089] The difference from Example 2 is that the first step is omitted, and NCM523 black powder is directly loaded into the tube furnace for the second step of two-stage reduction and the third step of physical sorting.

[0090] Comparative Example 3:

[0091] A cathode material precursor is prepared by the following method:

[0092] Step 1: Place NCM523 black powder in a microwave tube furnace, introduce a mixture of 10% H2 and 90% Ar (flow rate 150 mL / min), and heat to 620℃ at 10℃ / min, then hold for 3 h for microwave hydrogen reduction.

[0093] Step 2: After the reduction product is cooled, deionized water is added at a solid-liquid ratio of 1:10. The mixture is stirred at room temperature for 30 minutes, and then filtered to separate the water leaching liquid and the water leaching residue. The water leaching residue is dried at 105℃ for 12 hours and then fed into a wet magnetic separator (slurry concentration 15%). The magnetic field strength is gradient-separated at 0.1T→0.3T→0.5T to collect the magnetic products.

[0094] The testing method for this application is as follows:

[0095] 1. Phase analysis (XRD): X-ray diffraction is used to analyze the phase composition of the products at each stage.

[0096] 2. Saturation magnetization (M) sDetermination: The hysteresis loops of the reduction and sorting products were measured using a vibrating sample magnetometer (VSM) at room temperature (298 K), with an applied magnetic field range of -20000 to +20000 Oe. Sample mass was 100–300 mg (accurate to 0.01 mg), calibrated with a pure nickel standard (54.56 emu / g). s Take the average value when the magnetization intensity in the high field region (|H|≥15000 Oe) approaches saturation, and repeat 3 times to take the average value.

[0097] 3. Elemental content (ICP-OES): Take 0.5 g of sample (accurate to 0.0001 g), digest with HNO3-HCl-HF-H2O2 using microwave, and then dilute to volume. Determine the mass concentration of Li, Ni, Co, and Mn using inductively coupled plasma optical emission spectrometry. The spiked recovery rate is controlled at 95%~105%, and the absolute deviation of parallel determinations is ≤0.5%.

[0098] 4. Ni₂P / Co₂P Magnetic Concentrate Grade Determination: The mass concentrations of Ni and Co in the magnetic concentrate were determined using ICP-OES. The (Ni+Co) grade (%) was calculated as follows: ,in and The values ​​represent the mass concentrations of Ni and Co (mg / L) as measured by ICP-OES, and V represents the volume of the digestion solution (mL). The sample mass is (g).

[0099] 5. Determination of Li3PO4 enriched phase purity: The mass concentration of Li in the light phase was determined by ICP-OES. The purity of the Li3PO4 enriched phase (%) = ,in The concentration of Li (mg / L) is measured by ICP-OES, and V is the volume of the digestion solution (mL). The sample mass (g) is the mass of the sample taken. This represents the molar mass of lithium phosphate. This is the atomic weight of lithium.

[0100] 6. Determination of purity of Mn3(PO4)2 enriched phase: The mass concentration of Li in the light phase was determined by ICP-OES. Purity of Mn3(PO4)2 enriched phase (%) = ,in V represents the mass concentration of Mn (mg / L) measured by ICP-OES, and V is the volume of the digestion solution (mL). The sample mass (g) is the mass of the sample taken. The molar mass of manganese phosphate is... This is the atomic weight of manganese.

[0101] 7. Sorting efficiency evaluation indicators:

[0102] Ni / Co recovery rate = ;

[0103] Li recovery rate = ;

[0104] Mn recovery rate = ;

[0105] Separation selectivity index (S) = The larger the S value, the better the separation selectivity between Ni / Co and Mn.

[0106] Please refer to Table 1 for the differences in preparation conditions of Examples 1-11, and Table 2 for the above test results of Examples 1-11 and Comparative Examples 1-3.

[0107] Table 1 Comparison of preparation conditions in Examples 1-11 of this application

[0108]

[0109] Table 2. Test results of cathode material precursors in Examples 1-11 and Comparative Examples 1-3 of this application.

[0110]

[0111] Referring to Tables 1 and 2, Examples 1-11 of this application release four metal elements from the original oxide lattice through phosphorylation, allowing them to recombine in their respective phosphate forms. Utilizing the differences in chemical stability and response to reducing atmosphere among Ni3(PO4)2, Co3(PO4)2, Mn3(PO4)2, and Li3PO4, a material basis is provided for subsequent differentiated transformation through reduction treatment. Based on this, the phosphate mixture is heated under a reducing atmosphere, causing the different phosphate components to undergo differentiated reduction transformations according to their own thermodynamic properties. This results in a cathode material precursor mixture containing multiple phases with different physical properties obtained in the same reduction process. Utilizing the differences in magnetic properties, density, and conductivity among these phases, the mixture can be separated into multiple single phases through physical sorting, yielding precursor products that can be directly used for cathode material regeneration. Examples 1-11 of this application can achieve simultaneous separation of Ni / Co, Li and Mn components without the need for wet process steps such as water immersion, which helps to eliminate the risk of high-salt wastewater generation. At the same time, the process is short, which helps to reduce energy consumption and reagent consumption in the recovery process.

[0112] In Example 6, the phosphate mixed phase was directly heated to the main reduction temperature and subjected to a one-stage reduction. Building upon Example 6, Example 2 further employed a two-stage reduction, setting a low-temperature induction period of 400℃~450℃ in the first stage to pre-activate the Ni / Co phosphate surface at a lower temperature. Table 2 shows that after low-temperature induction activation, the diffraction peaks of Ni / Co phosphate completely disappeared, while the diffraction peaks of Ni2P / Co2P became sharper and more complete. The yield and purity of the magnetic product were significantly improved, indicating that the low-temperature induction period helps weaken the PO bonds of Ni / Co phosphate and form a highly reactive metastable precursor, thereby overcoming the kinetic barrier of low-temperature reduction and creating favorable conditions for full conversion during the main reduction period.

[0113] In Example 7, the main reduction temperature was 540℃ (one-stage reduction). Based on Example 7, Example 2 further employed a two-stage reduction while controlling the second-stage reduction temperature below 530℃. Table 2 shows that when the temperature was controlled below 530℃, no Mn2P phase was detected in the reduction product, and the purity and recovery rate of the Mn3(PO4)2 enriched phase remained at a high level. This indicates that controlling the reduction temperature below 530℃ helps maintain the thermodynamic stability of Mn3(PO4)2, preventing it from being reduced to ferromagnetic Mn2P, thereby preventing Mn from migrating to the magnetic product phase and facilitating the high selective separation between Ni / Co and Mn.

[0114] In Example 8, the main reduction temperature was 600℃ (one-stage reduction). Based on Example 8, Example 2 further employed a two-stage reduction while controlling the second-stage reduction temperature below 530℃. As shown in Table 2, in the low-temperature range, Ni / Co phosphate was selectively reduced to Ni2P / Co2P metal phosphide rather than a metal alloy, and Mn3(PO4)2 retained its phosphate phase. This resulted in more significant differences in magnetism and density between the phases, indicating that controlling the reduction temperature to no more than 530℃ helps Ni / Co and Mn / Li form phases with more significant differences in physical properties, providing a more favorable phase basis for subsequent physical separation.

[0115] Example 9 employed a two-stage reduction process, with the second-stage reduction temperature at 540°C. Building upon Example 9, Example 2 further controlled the second-stage reduction temperature below 530°C. Table 2 shows that even with a two-stage process, the reduction reaction of Mn3(PO4)2 is still triggered when the second-stage temperature exceeds 530°C, while maintaining the stability of each phase when the temperature is below 530°C. This indicates that 530°C is a universally applicable critical temperature boundary, and controlling the second-stage reduction temperature below this boundary is crucial to ensuring that Mn is not reduced.

[0116] The phosphorylation pretreatment in Example 10 was carried out at 250°C. Based on Example 10, Example 2 further increased the phosphorylation temperature to above 300°C. As shown in Table 2, when the phosphorylation temperature reaches above 300°C, the diffraction peaks of the layered structure of NCM completely disappear, and the metal element is fully converted into the phosphate precursor. The formation of Ni2P / Co2P in the subsequent reduction process is more complete. This indicates that controlling the phosphorylation temperature to be no lower than 300°C helps to fully destroy the layered structure of NCM and achieve complete phosphorylation of the metal element, thereby providing a good phase basis for subsequent selective reduction.

[0117] Example 11 uses single magnetic separation to separate the reduced phase. Building upon Example 11, Example 2 further introduces airflow staging and electrostatic separation as the second and third stages of separation. Table 2 shows that after three stages of separation, the purity of both the Li3PO4-enriched phase and the Mn3(PO4)2-enriched phase was further improved, and the recovery rates of Li and Mn were also further increased. This indicates that by introducing airflow staging and electrostatic separation on top of magnetic separation, the density and conductivity differences between different phases can be utilized for step-by-step separation. The combination of these three physical separation methods helps to achieve simultaneous and fine separation of the three components.

[0118] Compared to Examples 1-11 of this application, Comparative Example 1 does not perform the second reduction treatment, but directly performs tertiary physical sorting on the product after the first phosphorylation pretreatment. As shown in Table 2, the reduction product of Comparative Example 1 contains only Li3PO4, Ni3(PO4)2, Co3(PO4)2, and Mn3(PO4)2 phases. s The magnetic flux density was only 0.2 emu / g (virtually non-magnetic), and magnetic separation could not effectively separate any magnetic products. The Ni+Co recovery rate was only 4.8%, the Mn recovery rate was only 9.3%, and the S value was only 1.1, indicating that the components in the unreduced phosphate mixture lacked sufficient magnetic differences, and physical separation could not achieve effective separation. Therefore, reduction treatment is an essential step in converting the phosphate mixture into phases with different physical properties.

[0119] Compared to Examples 1-11 of this application, Comparative Example 2 did not undergo the first step of phosphorylation pretreatment, but instead directly subjected the NCM black powder to a two-stage reduction and three-stage physical separation. As shown in Table 2, the main phases in the reduction products of Comparative Example 2 were Ni-Co alloy, MnO, and Li2O, with no Ni2P / Co2P or Mn3(PO4)2 formed. The Ni+Co grade in its Ni2P / Co2P concentrate was 80.3%, but the Li3PO4 enriched phase was undetectable (Li exists in the form of Li2O and is unstable in water). The Li recovery rate was only 58.4%, and the separation selectivity index S value was only 15.2. This indicates that without phosphorylation pretreatment, the metal oxides in NCM cannot be converted into metal phosphides and phosphates with sufficient phase differences during the reduction process. The physical property differences between Ni / Co and Mn / Li are insufficient to support subsequent physical separation, and Li is severely lost due to failure to be anchored by phosphate ions. Therefore, phosphorylation pretreatment is an important prerequisite for constructing the target phase and achieving effective Li recovery.

[0120] Compared to Examples 1-11 of this application, Comparative Example 3 uses a single-stage microwave hydrogen reduction at 620℃, followed by wet gradient magnetic separation after water immersion treatment. As shown in Table 2, the reduction products of Comparative Example 3 are Ni-Co alloy, MnO, and LiOH·H2O (entering the water immersion phase), a completely different phase composition from Example 2. The magnetic product has a Ni+Co grade of 85.3%, a Ni+Co recovery rate of 90.2%, and a Li recovery rate of 92.3% (requiring water immersion extraction). However, Mn could not be recovered separately (it was mixed into the magnetic product or residue in the form of MnO). The separation selectivity index S value was only 10.4, indicating that reducing NCM without phosphorylation pretreatment at temperatures above 550℃ produces a conventional combination of metal / alloy and metal oxide, making effective separation of Ni / Co and Mn difficult. Furthermore, a water immersion step is required to recover lithium, making a completely dry separation impossible. This application obtains a phase combination of Ni2P / Co2P, Li3PO4 and Mn3(PO4)2 by combining phosphorylation pretreatment with two-stage low-temperature reduction at ≤530℃. With the addition of three-stage combined sorting, it achieves highly selective separation of Ni / Co and Mn (S value up to 142.7) and efficient recovery of Li (98.6%), without the need for a water immersion step.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a cathode material precursor, characterized in that, Includes the following steps: Waste lithium nickel cobalt manganese oxide cathode material is mixed with a phosphoric acid source and then subjected to heat treatment to convert the metal elements in the waste lithium nickel cobalt manganese oxide cathode material into phosphates, thus preparing a phosphate mixed phase. The phosphate mixed phase was heated under a reducing atmosphere to undergo reduction treatment, thereby obtaining a cathode material precursor mixed phase. The cathode material precursor mixture is separated by physical sorting to obtain the cathode material precursor.

2. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (1) The mass ratio of the waste lithium nickel cobalt manganese oxide cathode material to the phosphoric acid source is 1:(0.3~0.8); (2) The phosphoric acid source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium polyphosphate; (3) The temperature of the heat treatment is 300℃~400℃; (4) The heat treatment time is 1 h to 2 h.

3. The preparation method according to claim 1, characterized in that, In the reduction treatment of the phosphate mixed phase by heating it in the reducing atmosphere, the heating temperature is ≤530℃.

4. The preparation method according to claim 3, characterized in that, The phosphate mixture is heated under the reducing atmosphere to undergo reduction treatment, including the following steps: The preparation method involves heating to a first temperature and holding at that temperature under a first reducing atmosphere, followed by heating from the first temperature to a second temperature and holding at that temperature under a second reducing atmosphere; the preparation method also satisfies at least one of the following conditions: (1) The second temperature is higher than the first temperature; (2) The content of reducing gas in the second reducing atmosphere is higher than the content of reducing gas in the first reducing atmosphere; (3) The heat preservation time at the second temperature is longer than that at the first temperature.

5. The preparation method according to claim 4, characterized in that, The preparation method also satisfies at least one of the following conditions: The first reducing atmosphere comprises H2 at a volume percentage of 2% to 5%; The first temperature is 400℃~450℃, and the holding time is 1 h~2 h; The second reducing atmosphere comprises H2 at a volume percentage of 5% to 10%; The second temperature is 480℃~530℃, and the holding time is 2 h~4 h.

6. The preparation method according to claim 1, characterized in that, The physical sorting includes at least one of magnetic separation, airflow classification, and electrostatic separation.

7. The preparation method according to claim 6, characterized in that, The physical sorting also satisfies at least one of the following conditions: (1) The magnetic field strength of the magnetic separation is 0.1 T~0.3 T; (2) The airflow velocity for the airflow grading is 2 m / s to 5 m / s; (3) The voltage of electrostatic separation is 15 kV~30 kV.

8. The preparation method according to claim 1, characterized in that, The cathode material precursor comprises one or more of the following independent phases: i) Ni2P / Co2P composite phase; ii) Li3PO4 phase; iii) Mn3(PO4)2 phase.

9. The preparation method according to claim 8, characterized in that, The independent phase also satisfies at least one of the following conditions: (1) In the Ni2P / Co2P composite phase, the grades of Ni and Co are ≥93%; (2) The purity of Li3PO4 in the Li3PO4 phase is ≥88%; (3) The purity of Mn3(PO4)2 in the Mn3(PO4)2 phase is ≥85%.

10. The application of the preparation method according to any one of claims 1-9 in the preparation of at least one of the following functional materials: i) NCM ternary precursor; ii) Lithium supplement for cathode materials; iii) Lithium iron manganese phosphate cathode material.

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