Separation and repair method of heterogeneous positive electrode black powder material

Abstract

The invention provides a method for separating and repairing a heterogeneous positive electrode black powder material, which comprises the following steps of: performing carbonization heat treatment on the heterogeneous positive electrode black powder material to obtain a carbonized heterogeneous positive electrode black powder material; mixing the carbonized heterogeneous positive electrode black powder material with a density heavy liquid, and carrying out cyclone separation treatment to respectively obtain a heavy product and a light product; and mixing the heavy product with a lithium source, and carrying out lithiation calcination treatment to obtain the nickel cobalt lithium manganate positive electrode material. Carrying out oxidation sintering treatment on the light product to obtain a sintered material, mixing the sintered material with a carbon source and a lithium source, and carrying out thermal reduction treatment to obtain a lithium iron phosphate positive electrode material; the heterogeneous anode black powder material comprises a mixed material of ternary nickel cobalt lithium manganate anode material black powder and lithium iron phosphate anode material black powder. According to the separation and restoration method, no strong acid, strong base or waste liquid is generated, no heavy metal is lost, efficient recovery and utilization of key elements on the material level are achieved, and density heavy liquid and water for washing can be recycled.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to a method for separating and repairing heterogeneous cathode black powder materials. Background Technology

[0002] With the booming development of the new energy vehicle industry and the rapid increase in market share, my country's power battery industry has experienced unprecedented growth. However, as a large number of batteries are put into use and gradually reach their designed lifespan, the number of retired batteries generated each year is increasing exponentially. If this massive waste resource cannot be disposed of efficiently and environmentally, it will not only cause persistent pollution to soil and water bodies due to the heavy metals and electrolytes it contains, but will also lead to a serious loss of key strategic metal resources such as lithium, cobalt, and nickel. Therefore, building a large-scale, green waste power battery recycling system and promoting its high-quality resource recycling has become an urgent task concerning resource security and sustainable environmental development.

[0003] Currently, the recycling of failed lithium-ion batteries mainly follows three technical paths: pyrometallurgy, hydrometallurgy, and direct repair. Pyrometallurgical and hydrometallurgical processes have been developed earlier and are relatively mature, but they generally suffer from lengthy processes, high energy consumption, and complex wastewater and waste gas treatment issues, facing pressure on both economic and environmental costs. In contrast, direct repair technology is an emerging method based on material structure reactivation and chemical lithium replenishment. It directly restores the electrochemical performance of the cathode material through a mild physicochemical process, offering significant advantages such as a shorter process, significantly reduced energy consumption and emissions, and high resource utilization. This technology not only aligns with the development direction of green manufacturing and the circular economy but also effectively shortens the recycling cycle and reduces dependence on primary minerals. Therefore, it is considered a key breakthrough in promoting the low-carbon and high-efficiency transformation and upgrading of the battery recycling industry, possessing extremely important strategic significance and application prospects.

[0004] In existing large-scale recycling processes, used batteries typically undergo pretreatment steps such as crushing and screening to obtain valuable components, primarily electrode materials. However, the failed electrode materials generated during industrial recycling are essentially a multiphase mixture containing various components, including positive electrode active materials, negative electrode active materials, conductive agents, binders, and residual electrolyte, commonly known as "black powder." This highly complex physical and chemical composition leads to significant differences in the microstructure, surface properties, and reactivity of each component, fundamentally restricting the adaptability and stability of direct repair processes and becoming a major technical barrier to the engineering application of this technology.

[0005] Especially driven by the current pursuit of high energy density and long driving range in new energy vehicles, battery companies are increasingly adopting composite cathode systems to balance the performance advantages of different cathode materials. This involves mixing two or more cathode materials in specific proportions. For example, combining high-capacity lithium nickel cobalt manganese oxide (NCM) with high-safety lithium iron phosphate (LFP) can improve the overall performance of the cell, but it also presents serious challenges for subsequent direct regeneration. NCM and LFP not only have vastly different crystal structures and lithium diffusion mechanisms, but their synthesis and regeneration require completely opposite thermodynamic environments. NCM typically needs to be stable in an oxidizing atmosphere for lithium replenishment and repair, while LFP needs to be in an inert or reducing atmosphere to prevent iron oxidation and maintain structural integrity. If the two are directly mixed and subjected to high-temperature regeneration, mutual interference is likely to occur, leading to material phase transitions, irreversible structural changes, intensified surface side reactions, and irreversible degradation of electrochemical performance.

[0006] Therefore, developing efficient and precise pre-separation technologies to achieve the orderly separation and enrichment of heterogeneous cathode materials has become a core prerequisite for breaking through the technical bottleneck of direct repair of mixed black powder and promoting its large-scale industrial application. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for separating and repairing heterogeneous cathode black powder materials. In the process flow of the separation and repair method described in this invention, no strong acids, strong alkalis, or waste liquids are generated, and no heavy metals are lost. This achieves efficient recovery and reuse of key elements at the material level. The dense heavy liquid and the water used for washing can be recycled. The comprehensive resource recovery rate is greater than 98%, and the carbon emissions are far lower than those of traditional wet and pyrometallurgical processes.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a method for separating and repairing heterogeneous cathode black powder materials, the method comprising the following steps:

[0010] Carbonization heat treatment was performed on heterogeneous cathode black powder material to obtain carbonized heterogeneous cathode black powder material;

[0011] Carbonized heterogeneous cathode black powder material was mixed with a dense heavy liquid and then subjected to hydrocyclone separation to obtain heavy and light products respectively.

[0012] The heavy product was mixed with a lithium source and then subjected to lithiation calcination to obtain a ternary lithium nickel cobalt manganese oxide cathode material.

[0013] Light products are oxidized and sintered to obtain sintered material. The sintered material is mixed with a carbon source and then thermally reduced to obtain lithium iron phosphate cathode material.

[0014] The heterogeneous cathode black powder material includes a mixture of ternary lithium nickel cobalt manganese oxide cathode material black powder and lithium iron phosphate cathode material black powder.

[0015] This invention involves heat-treating a heterogeneous cathode material composed of spent ternary nickel-cobalt-manganese lithium oxide (NCM) and spent lithium iron phosphate (LFP) cathode material, followed by carbonizing the binder, separator, and other materials to obtain a carbonized heterogeneous cathode material. This material comprises three components: spent ternary nickel-cobalt-manganese oxide (NCM), spent lithium iron phosphate (LFP), and carbon materials. The actual density of NCM is 4 g / cm³. 3 ~5g / cm 3 The actual density of LFP is 2 g / cm³. 3 ~2.6g / cm 3 The density of carbon materials is 2.25 g / cm³. 3 ~2.26g / cm 3 Since LFP and carbon materials have similar densities, mixing carbonized heterogeneous cathode black powder with a dense heavy liquid allows for the separation of the heterogeneous cathode black powder through cyclone separation based on their density differences. During cyclone separation, particles undergo intense collisions and friction in the high-speed fluid. This physical action effectively strips away the loose side reaction layers (such as lithium carbonate and LiF) and residual carbon films on the surface of the failed material, exposing relatively fresh active material crystal faces. This enables surface and interface control of the particles, significantly reducing the solid-state reaction energy barrier in subsequent direct repair processes. The mixed slurry is pumped in through the inlet and moves in a spiral motion. Due to density differences, heavier particles gradually sink while lighter particles overflow, thus separating NCM from LFP and carbon materials, yielding failed LFP carbon-containing slurry (light product) and failed NCM slurry (heavy product). Failed NCM can be repaired by direct lithiation and calcination to obtain ternary lithium nickel cobalt manganese oxide cathode material. The carbon-containing LFP material is first oxidized and sintered to remove the carbon and obtain a mixture of Li3Fe2(PO4)3 and Fe2O3. The mixture of Li3Fe2(PO4)3 and Fe2O3 is supplemented with a carbon source and then subjected to thermal reduction treatment to obtain lithium iron phosphate cathode material.

[0016] This invention achieves a separation efficiency (based on metal element content) of over 95% for failed NCM and failed LFP through heavy liquid + swirling, laying the foundation for subsequent high-quality repair. The in-situ surface regulation during the swirling process removes the ion diffusion barrier, which reduces the temperature of the subsequent solid-phase lithium replenishment reaction by 50°C to 100°C and shortens the time by about 30%, while also resulting in more complete lattice repair of the material.

[0017] Preferably, the atmosphere for the carbonization heat treatment includes nitrogen and / or argon.

[0018] Preferably, the temperature of the carbonization heat treatment is 450℃~720℃, for example: 450℃, 500℃, 600℃, 700℃ or 720℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] The carbonization heat treatment performed at the above-mentioned temperature can not only remove organic binders, but also realize the transformation of organic matter into amorphous carbon by precisely controlling the temperature window. At the same time, it can preserve the main crystal structure of NCM and LFP to the greatest extent and create a material basis with uniform surface properties for subsequent density-based separation.

[0020] Preferably, the density heavy liquid comprises ferrosilicon heavy suspension and / or sodium polytungstate aqueous solution.

[0021] This invention utilizes a suitable type of density heavy liquid to effectively separate NCM and LFP in heterogeneous cathode black powder. In the laboratory, sodium polytungstate aqueous solution can be used, and the density can be adjusted by the concentration of sodium polytungstate. In industrial separation, ferrosilicon heavy suspension is used. By adjusting the ratio of high-density ferrosilicon to water and adding a small amount of stabilizer (such as bentonite), a stable and appropriately dense density heavy liquid can be obtained.

[0022] Preferably, the density of the heavy liquid is 2.8 g / cm³. 3 ~4g / cm 3 For example: 2.8g / cm 3 3g / cm 3 3.2g / cm 3 3.5g / cm 3 or 4g / cm 3 The term "etc." is not limited to the listed values; it also applies to other unlisted values ​​within the range.

[0023] Preferably, the mass-to-volume ratio of the carbonized heterogeneous cathode black powder material to the dense heavy liquid is (5~20):100, for example: 5:100, 8:100, 10:100, 15:100 or 20:100, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, after the cyclone separation process, the resulting heavy and light products are subjected to pressure filtration and drying processes, respectively.

[0025] Preferably, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, or lithium oxalate. Typical but non-limiting combinations include combinations of lithium hydroxide and lithium carbonate, combinations of lithium hydroxide and lithium oxalate, or combinations of lithium oxalate and lithium carbonate.

[0026] Preferably, the atmosphere for the lithium calcination treatment includes an oxygen-containing atmosphere.

[0027] The present invention obtains highly active failed NCM after swirl treatment, which can be directly lithiated and calcined to efficiently complete lithium replenishment and crystal structure rearrangement. The atmosphere of the lithiation and calcination treatment depends on the nickel content in the ternary nickel cobalt manganese oxide cathode material. The oxygen atmosphere for high nickel cathode materials (such as NCM811) is an oxygen atmosphere, and the oxygen atmosphere for low nickel cathode materials (such as NCM523) is an air atmosphere.

[0028] Preferably, the lithiation calcination temperature is 650℃~750℃, for example: 650℃, 680℃, 700℃, 720℃ or 750℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the lithiation calcination time is 2h to 5h, for example: 2h, 2.5h, 3h, 4h or 5h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the atmosphere for the oxidation sintering treatment includes an oxygen-containing atmosphere.

[0031] The oxygen-containing atmosphere described in this invention includes air or a mixture of oxygen and nitrogen. The chemical equations for the reactions occurring during the oxidation sintering process are as follows:

[0032] 12LiFePO4+3O2→4Li3Fe2(PO4)3+2Fe2O3;

[0033] C + O2 → CO2.

[0034] Preferably, the temperature of the oxidation sintering treatment is 400℃~600℃, for example: 400℃, 450℃, 500℃, 550℃ or 600℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the oxidation sintering treatment time is 1h to 3h, for example: 1h, 1.5h, 2h, 2.5h or 3h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the carbon source includes any one or a combination of at least two of glucose, sucrose, or urea.

[0037] Preferably, the mass ratio of the sintering material to the carbon source is 1:(0.03~0.15), for example: 1:0.03, 1:0.05, 1:0.1, 1:0.12 or 1:0.15, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the atmosphere for the thermal reduction treatment includes a hydrogen-containing protective gas.

[0039] The hydrogen-containing protective gas described in this invention is a mixture of hydrogen and a protective gas, including nitrogen or argon.

[0040] The chemical equation for the reaction occurring during the thermal reduction treatment is as follows:

[0041] C6H 12 O6+8Li3Fe2(PO4)3+4Fe2O3→24LiFePO4+6H2O+6CO2.

[0042] Preferably, the temperature of the heat reduction treatment is 550℃~660℃, for example: 550℃, 580℃, 600℃, 630℃ or 660℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the heat reduction treatment time is 1h to 3h, for example: 1h, 1.5h, 2h, 2.5h or 3h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] The light products rich in LFP contain impurities of carbon. This invention addresses this issue through a two-step process: controlled oxidation to remove these impurities and supplementation with a highly active reducing carbon source. This achieves the desired reduction of Fe... 2+ To Fe 3+ directional oxidation, Fe 3+ To Fe 2+ The process involves the directional reduction and reconstruction of the LiFePO4 phase. This method utilizes the removal of impurity carbon and the addition of functional carbon to directly repair failed LFPs, and the steps are simple and efficient.

[0045] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) This invention focuses on "physical separation," utilizing the density difference between NCM and LFP in heterogeneous cathode black powder to separate failed NCM and LFP by cyclone separation, while simultaneously controlling the surface and interface. Subsequently, lithium replenishment is performed to repair them, yielding ternary lithium nickel cobalt manganese oxide materials and lithium iron phosphate cathode materials, respectively. This provides a solution for the recovery of cathode material mixtures with vastly different physicochemical properties, such as NCM / LFP, without the need for dissolution or complex chemical separation. It completely eliminates the long process of "acid leaching-precipitation-resynthesis," avoiding the use of large amounts of acid and alkali reagents, expensive liquid-solid separation equipment, and complex wastewater treatment procedures. The main process involves physical operation and solid-phase sintering, with highly versatile equipment. Energy consumption and operating costs are expected to be reduced by more than 30%.

[0048] (2) The NCM and LFP materials obtained by the separation and repair method described in this invention can recover to more than 95% of the key electrochemical indicators such as the first discharge specific capacity and cycle stability of the corresponding commercial new materials, which meets the requirements for battery-grade use.

[0049] (3) The NCM separation efficiency of the separation and repair method of the heterogeneous cathode black powder material described in this invention can reach more than 99.5%, the NCM recovery rate can reach more than 98.1%, the LFP recovery rate can reach more than 96.7%, the specific capacity of NCM after repair can reach more than 193mAh / g, the specific capacity of LFP can reach more than 149%, the capacity retention rate of NCM after repair after 100 cycles can reach more than 99.1%, and the capacity retention rate of LFP after repair after 100 cycles can reach more than 99.4%. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the process flow for the separation and repair method of heterogeneous cathode black powder material according to an embodiment of the present invention.

[0051] Figure 2 This is a schematic diagram of the cyclone separation equipment used in the cyclone separation process described in the embodiments of the present invention.

[0052] Figure 3 This is a SEM image of the heterogeneous cathode black powder material described in Embodiment 1 of the present invention.

[0053] Figure 4 This is an SEM image of the light product described in Embodiment 1 of the present invention.

[0054] Figure 5 This is an SEM image of the heavy product described in Embodiment 1 of the present invention.

[0055] Figure 6 This is a SEM image of the ternary lithium nickel cobalt manganese oxide cathode material repaired as described in Example 1 of this invention.

[0056] Figure 7This is a SEM image of the lithium iron phosphate cathode material repaired as described in Example 1 of this invention. Detailed Implementation

[0057] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0058] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0059] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0060] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0061] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0062] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0063] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0064] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0065] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0066] The heterogeneous cathode black powder material described in this invention is derived from actual enterprise production. The commonly used ratio of NCM811 cathode to LFP cathode in the black powder mixture is 9:1, 8:2, 7:3, 6:4, 5:5, etc., and the proportion of binder, carbon impurities, etc. is 5~15%.

[0067] All examples used NCM811:LFP = 7:3 black powder.

[0068] Example 1

[0069] This embodiment provides a method for separating and repairing heterogeneous cathode black powder materials. A schematic diagram of the process flow of the separation and repair method is shown below. Figure 1 As shown, the separation and repair method includes the following steps:

[0070] The heterogeneous cathode black powder material was subjected to carbonization heat treatment at 600°C under a nitrogen atmosphere to obtain carbonized heterogeneous cathode black powder material. The SEM image of the heterogeneous cathode black powder material is shown below. Figure 3 As shown;

[0071] Carbonized heterogeneous cathode black powder material with a density of 3.5 g / cm³ 3 Sodium polytungstate aqueous solution was mixed at a mass ratio of 15:100, and then... Figure 2 The hydrocyclone separator shown performs hydrocyclone separation. Exhausted NCM slurry (heavy product) and exhausted LFP carbon-containing slurry (light product) are collected from the underflow and overflow outlets of the separator, respectively. These are then filtered (to obtain the heavy liquid for recycling), washed with water, and dried at 100°C to obtain exhausted NCM and LFP carbon-containing materials, respectively. The SEM image of the light product is shown below. Figure 4 As shown, the SEM image of the heavy product is as follows. Figure 5 As shown;

[0072] The heavy product was mixed with lithium carbonate in an elemental ratio of Ni+Co+Mn:Li = 1:1.02, and then subjected to lithiation calcination at 700°C for 3.5 h in an oxygen atmosphere to obtain the repaired ternary nickel-cobalt-manganese lithium oxide cathode material. The SEM image of the repaired ternary nickel-cobalt-manganese lithium oxide cathode material is shown below. Figure 6 As shown;

[0073] The light product was oxidized and sintered in air at 500°C for 2 hours to obtain a sintered material. The sintered material was then mixed with glucose at a ratio of 1:0.05, and subjected to thermal reduction treatment at 600°C for 2 hours under a hydrogen-containing protective atmosphere with a hydrogen to nitrogen volume ratio of 5:100 to obtain the repaired lithium iron phosphate cathode material. The SEM image of the repaired lithium iron phosphate cathode material is shown below. Figure 7 As shown;

[0074] Depend on Figure 3-7 It can be seen that the heterogeneous cathode black powder material of this invention contains multiple components such as degraded NCM, degraded LFP, impurity carbon, and graphite. After "heavy liquid + cyclone" treatment, light and heavy products are obtained. It can be found that the light product ( Figure 4 It mainly consists of a mixture of degraded LFP and graphite, with heavy products ( Figure 5 These are damaged secondary NCM particles. After lithium replenishment repair, the NCM can be restored to complete particles. Figure 6 ), reaching a commercial level. Similarly, LFP can also be restored to a commercial profile ( Figure 7 ).

[0075] Example 2

[0076] This embodiment provides a method for separating and repairing heterogeneous cathode black powder materials. A schematic diagram of the process flow of the separation and repair method is shown below. Figure 1 As shown, the separation and repair method includes the following steps:

[0077] The heterogeneous cathode black powder material was subjected to carbonization heat treatment at 450°C under a nitrogen atmosphere to obtain carbonized heterogeneous cathode black powder material.

[0078] Carbonized heterogeneous cathode black powder material with a density of 2.8 g / cm³ 3 The ferrosilicon heavy suspension (containing bentonite stabilizer) was mixed at a mass ratio of 15:100, and then... Figure 2 The cyclone separator shown is used for cyclone separation. Exhausted NCM slurry (heavy product) and exhausted LFP carbon-containing slurry (light product) are collected from the underflow and overflow of the cyclone separator, respectively. They are then filtered by pressure (to obtain heavy liquid for recycling), washed with water, and dried at 100°C to obtain exhausted NCM and exhausted LFP carbon-containing materials, respectively.

[0079] The heavy product was mixed with lithium carbonate in a ratio of Ni+Co+Mn:Li=1:1.02, and then calcined at 650°C in an oxygen atmosphere for 5 hours to obtain the repaired ternary nickel-cobalt-manganese lithium oxide cathode material.

[0080] The light product was oxidized and sintered in air at 400°C for 3 hours to obtain sintered material. The sintered material was mixed with glucose at a ratio of 1:0.05 and subjected to thermal reduction treatment at 550°C for 3 hours in a hydrogen-containing protective atmosphere with a hydrogen to nitrogen volume ratio of 5:100 to obtain the repaired lithium iron phosphate cathode material.

[0081] Example 3

[0082] This embodiment provides a method for separating and repairing heterogeneous cathode black powder materials. A schematic diagram of the process flow of the separation and repair method is shown below. Figure 1 As shown, the separation and repair method includes the following steps:

[0083] The heterogeneous cathode black powder material was subjected to carbonization heat treatment at 720°C under a nitrogen atmosphere to obtain carbonized heterogeneous cathode black powder material.

[0084] Carbonized heterogeneous cathode black powder material with a density of 4 g / cm³ 3 The ferrosilicon heavy suspension (containing bentonite stabilizer) was mixed at a mass ratio of 15:100, and then... Figure 2 The cyclone separator shown is used for cyclone separation. Expired NCM slurry (heavy product) and exhausted LFP carbon-containing slurry (light product) are collected from the underflow and overflow of the cyclone separator, respectively. They are then filtered by pressure (to obtain heavy liquid for recycling), washed with water, and dried at 100°C to obtain LFP carbon-containing material and exhausted NCM, respectively.

[0085] The heavy product was mixed with lithium carbonate in a ratio of Ni+Co+Mn:Li=1:1.02, and then calcined at 750°C in an oxygen atmosphere for 2 hours to obtain the repaired ternary nickel cobalt manganese oxide cathode material.

[0086] The light product was oxidized and sintered in air at 600°C for 1 hour to obtain sintered material. The sintered material was mixed with glucose at a ratio of 100:5 and then thermally reduced at 660°C for 1 hour in a hydrogen-containing protective atmosphere with a hydrogen to nitrogen volume ratio of 5:100 to obtain the repaired lithium iron phosphate cathode material.

[0087] Example 4

[0088] The only difference between this embodiment and Embodiment 1 is that the carbonization heat treatment temperature is 400℃, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0089] Example 5

[0090] The only difference between this embodiment and Embodiment 1 is that the carbonization heat treatment temperature is 750°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0091] Example 6

[0092] The only difference between this embodiment and Example 1 is that the density of the sodium polytungstate aqueous solution is 2.5 g / cm³. 3 Other conditions and parameters are exactly the same as in Example 1.

[0093] Example 7

[0094] The only difference between this embodiment and Example 1 is that the density of the sodium polytungstate aqueous solution is 4.2 g / cm³. 3 Other conditions and parameters are exactly the same as in Example 1.

[0095] Example 8

[0096] The only difference between this embodiment and Embodiment 1 is that the temperature of the heat reduction treatment is 520°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0097] Example 9

[0098] The only difference between this embodiment and Embodiment 1 is that the temperature of the heat reduction treatment is 680°C, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0099] Comparative Example 1

[0100] The only difference between this embodiment and Embodiment 1 is that the cyclone separation is replaced with spiral chute separation; all other conditions and parameters are exactly the same as in Embodiment 1.

[0101] Comparative Example 2

[0102] This comparative example uses a wet recovery process, specifically including the following steps:

[0103] (1) Acid leaching: The failed positive electrode black powder is mixed with 2M hydrochloric acid solution at a solid-liquid ratio of 50g / L, and 1.5vol% hydrogen peroxide is added as a reducing agent. The mixture is reacted in a stirred leaching reactor at 90℃ for 2h to convert valuable metals such as Li, Ni, Co, Mn and Fe in the black powder into ions that enter the solution.

[0104] (2) Fractional precipitation and solution preparation: The leachate was filtered, and the pH of the filtrate was first adjusted to 3.5 with 30wt% sodium hydroxide solution. Fe was then precipitated and filtered to remove the precipitate. 3+ And Al 3+ Impurities were removed. Subsequently, an aqueous sodium hypochlorite solution (10% available chlorine content, NaClO / Co molar ratio 3:1) was added to the filtrate. The mixture was stirred at pH 3 and room temperature for 30 minutes, selectively precipitating Co₂O₃·3H₂O, which was then separated by pressure filtration. The filtrate after cobalt separation was further adjusted to pH 11 with sodium hydroxide, and after stirring, Ni(OH)₂ precipitated, which was then separated by pressure filtration. Thus, three intermediate products were obtained: cobalt slag, nickel slag, and a product rich in Mn. 2+ With Li + The filtrate.

[0105] (3) Precursor regeneration and cathode material resynthesis: The separated nickel slag (Ni(OH)2) and cobalt slag (Co2O3·3H2O) are dissolved separately and then mixed with Mn-rich materials. 2+ and Li + The filtrate was prepared according to the required stoichiometric ratio of the product (e.g., Ni:Co:Mn=8:1:1; Ni+Co+Mn:Li=1:1.02 when preparing NCM811). The corresponding ternary carbonate precursor (Ni...) was prepared by co-precipitation under conditions of pH=7.8, 55℃, and ammonia complexation. 0.8 Co 0.1 Mn 0.1 After filtering to obtain the precursor, the remaining mother liquor mainly contains lithium, which can be precipitated and recovered as high-purity Li₂CO₃ by passing it through a saturated sodium carbonate solution. The precursor and the recovered lithium carbonate are uniformly mixed at a Li / (Ni+Co+Mn) molar ratio of 1.05:1, and sintered at 900℃ for 12 hours under an oxygen atmosphere to regenerate a layered ternary cathode material. In addition, the separated iron precipitate (Fe(OH)₃) is used as an iron source and mixed with the recovered Li₂CO₃ and phosphorus source in a stoichiometric ratio. 5% carbon source is added, and the mixture is sintered at 700℃ for 10 hours under an inert atmosphere to obtain carbon-coated lithium iron phosphate (LFP) cathode material.

[0106] Comparative Example 3

[0107] This comparative example uses commercially available NCM811 material.

[0108] Comparative Example 4

[0109] This comparative example uses commercially available LFP materials.

[0110] Performance testing:

[0111] The performance tests mainly determined the separation efficiency of NCM and LFP, the material recovery rate, and the electrochemical performance of the battery assembled with the repaired materials (Comparative Example 1 recovers metal elements by wet process). The test results are shown in Table 1:

[0112] Table 1

[0113]

[0114] As shown in Table 1, and based on Examples 1 to 3, the NCM separation efficiency of the separation and repair method for heterogeneous cathode black powder materials described in this invention can reach over 99.5%, the NCM recovery rate can reach over 98.1%, the LFP recovery rate can reach over 96.7%, the specific capacity of the repaired NCM can reach over 193 mAh / g, the specific capacity of the LFP can reach over 149%, the capacity retention rate of the repaired NCM material after 100 cycles can reach over 99.1%, and the capacity retention rate of the repaired LFP material after 100 cycles can reach over 99.4%.

[0115] Comparing Examples 1 and 4-5, it can be seen that in the separation and repair method of heterogeneous cathode black powder material of the present invention, the temperature of carbonization heat treatment affects the separation and repair effect. Controlling the temperature of carbonization heat treatment at 450℃~720℃ results in a better separation and repair effect. If the temperature of carbonization heat treatment is too high, lithium inside the cathode material will be lost, affecting the subsequent lithium replenishment process (increase in lithium content) and the material repair effect. If the temperature of carbonization heat treatment is too low, the binder cannot be completely carbonized, resulting in mixed powder still having mixed powder agglomerates, making further separation difficult.

[0116] A comparison of Examples 1 and 6-7 shows that in the separation and repair method of heterogeneous cathode black powder material described in this invention, the density of the heavy liquid affects the separation and repair effect. The density of the heavy liquid should be controlled at 2.8 g / cm³. 3 ~4g / cm 3 The separation and remediation effect is relatively good. If the density of the heavy liquid is too high, the light products will contain some NCM, affecting the purity of LFP products. The proportion of LFP will lead to a decrease in the specific capacity of the final remediated LFP electrochemical performance test. If the density of the carbon-density heavy liquid is too low, the heavy products will contain LFP and carbon materials. In a further oxidizing atmosphere, LFP decomposes into iron phosphate, and the proportion of LFP will lead to a decrease in the specific capacity of the final remediated NCM electrochemical performance test.

[0117] A comparison of Examples 1 and 8-9 shows that in the separation and repair method of heterogeneous cathode black powder materials described in this invention, the temperature of the thermal reduction treatment affects the separation and repair effect. Controlling the thermal reduction treatment temperature between 550℃ and 660℃ results in a better separation and repair effect. If the thermal reduction treatment temperature is too high, the carbon source loss is too large, the carbon material's coating effect on the LFP surface is poor, leading to poor conductivity and poor capacity performance in electrochemical performance testing. If the thermal reduction treatment temperature is too low, some carbon sources cannot be completely carbonized, resulting in poor conductivity, affecting capacity performance, and the proportion of carbon sources also leads to a decrease in the specific capacity of the finally repaired LFP in electrochemical performance testing.

[0118] As can be seen from the comparison between Example 1 and Comparative Example 1, in the separation and repair method of heterogeneous cathode black powder material of the present invention, the separation of heterogeneous cathode black powder can be achieved by cyclone separation. During the cyclone separation process, the particles undergo violent collision and friction in the high-speed fluid. This physical action can effectively peel off the loose side reaction layer (such as lithium carbonate, LiF, etc.) and residual carbon film on the surface of the failed material, exposing the relatively fresh active material crystal surface, thereby achieving surface modification of the particles and significantly reducing the reaction energy barrier in the subsequent direct repair process.

[0119] As can be seen from the comparison of Example 1 and Comparative Examples 2-4, this invention takes "physical separation" as its core, and utilizes the density difference of heterogeneous cathode black powder to separate and repair failed NCM and failed LFP, respectively, to obtain ternary lithium nickel cobalt manganese oxide cathode materials and lithium iron phosphate cathode materials. This provides a solution for the recycling of cathode material mixtures with different physicochemical properties, such as NCM / LFP, without the need for dissolution or complex chemical separation. It completely eliminates the long process of "acid leaching-precipitation-resynthesis", avoids the use of a large amount of acid and alkali reagents, expensive liquid-solid separation equipment, and complex wastewater treatment processes. The key electrochemical indicators such as the first discharge specific capacity and cycle stability of the obtained NCM and LFP materials can be restored to more than 95% of the corresponding commercial new materials, meeting the requirements for battery-grade use.

[0120] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for separating and repairing heterogeneous cathode black powder materials, characterized in that, The separation and repair method includes the following steps: Carbonization heat treatment was performed on heterogeneous cathode black powder material to obtain carbonized heterogeneous cathode black powder material; Carbonized heterogeneous cathode black powder material was mixed with a dense heavy liquid and then subjected to hydrocyclone separation to obtain heavy and light products respectively. The heavy product was mixed with the first lithium source and then subjected to lithiation calcination to obtain a ternary lithium nickel cobalt manganese oxide cathode material. Light products are oxidized and sintered to obtain sintered material. The sintered material, carbon source and second lithium source are mixed and thermally reduced to obtain lithium iron phosphate cathode material. The heterogeneous cathode black powder material includes a mixture of ternary lithium nickel cobalt manganese oxide cathode material black powder and lithium iron phosphate cathode material black powder.

2. The separation and repair method as described in claim 1, characterized in that, The atmosphere for the carbonization heat treatment includes nitrogen and / or argon. And / or, the temperature of the carbonization heat treatment is 450℃~720℃.

3. The separation and repair method as described in claim 1, characterized in that, The density heavy liquid includes ferrosilicon heavy suspension and / or sodium polytungstate aqueous solution; And / or, the density of the heavy liquid is 2.8 g / cm³. 3 ~4g / cm 3 .

4. The separation and repair method as described in claim 1, characterized in that, The mass ratio of the carbonized heterogeneous cathode black powder material to the density heavy liquid is (5~20):

100.

5. The separation and repair method as described in claim 1, characterized in that, The heavy and light products obtained after the hydrocyclone separation process are subjected to pressure filtration and drying, respectively.

6. The separation and repair method as described in claim 1, characterized in that, The first lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, or lithium oxalate.

7. The separation and repair method as described in claim 1, characterized in that, The atmosphere for the lithium calcination treatment includes an oxygen-containing atmosphere; And / or, the lithiation calcination temperature is 650℃~750℃; And / or, the lithiation calcination time is 2h~5h.

8. The separation and repair method as described in claim 1, characterized in that, The atmosphere for the oxidation sintering treatment includes an oxygen-containing atmosphere; And / or, the temperature of the oxidation sintering treatment is 400℃~600℃; And / or, the oxidation sintering treatment time is 1h to 3h.

9. The separation and repair method as described in claim 1, characterized in that, The carbon source includes any one or a combination of at least two of glucose, sucrose, or urea. And / or, the mass ratio of the sintered material to the carbon source is 1:(0.03~0.15); And / or, the second lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, or lithium oxalate; And / or, the mass ratio of the sintered material to the second lithium source is 100:(1~3).

10. The separation and repair method as described in claim 1, characterized in that, The atmosphere for the thermal reduction treatment includes a hydrogen-containing protective gas; And / or, the temperature of the thermal reduction treatment is 550℃~660℃; And / or, the heat reduction treatment time is 1h to 3h.

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