Method for recycling positive and negative black powder of waste battery, slurry processing and separating device and repaired lithium iron phosphate material

Abstract

The application provides a recovery method of positive and negative black powder of waste batteries, a slurry processing and separating device and a repaired lithium iron phosphate material, and belongs to the technical field of recycling of waste batteries. The recovery method comprises the following steps: mixing the positive and negative black powder and a solvent to obtain positive and negative black powder slurry; wherein the positive and negative black powder comprises lithium iron phosphate black powder particles and graphite; the positive and negative black powder slurry is subjected to homogenization treatment to obtain homogenized material, and then the positive and negative products are separated; wherein the homogenized material comprises modified lithium iron phosphate particles and graphene. The recovery method realizes the separation of the lithium iron phosphate material and the graphite, the dispersion of the agglomerates and the modification of the surface of the lithium iron phosphate material, and the conversion of the graphite into graphene. In addition, the recovery method is flexible in cooperation with the slurry processing and separating device, and is beneficial to improving the large-scale processing efficiency. Moreover, in combination with the solid-phase lithium supplement repair technology, the efficient direct repair of the structure and performance of the failed lithium iron phosphate can be realized.

Description

Technical Field

[0001] This invention belongs to the field of waste battery recycling technology, specifically relating to a method for recycling positive and negative electrode black powder from waste batteries, a slurry processing and separation device, and repaired lithium iron phosphate material. Background Technology

[0002] With the continued expansion of the new energy vehicle market and the increasing number of vehicles, the power battery industry has experienced significant growth. However, as more and more batteries enter the market and gradually reach the end of their service life, the number of batteries retired each year is also increasing annually. If these large quantities of used batteries are not properly disposed of, they will not only pose a serious threat to the environment but also lead to a huge waste of resources. Therefore, establishing an effective recycling system for used power batteries and promoting their reuse has become an urgent task.

[0003] There are three main methods for recycling and reusing spent lithium-ion batteries: pyrometallurgy, hydrometallurgy, and direct regeneration. Pyrometallurgical and hydrometallurgical methods have the advantage of mature technology, but they typically involve long processing cycles and complex wastewater and waste gas treatment processes, leading to higher costs. Direct regeneration, on the other hand, is a repair method developed based on lithium replenishment technology. It features a short regeneration process, low pollution emissions, and low energy consumption costs, and has broad application prospects.

[0004] However, current methods for processing large quantities of waste batteries typically involve direct crushing and screening to obtain valuable components. The more economically valuable cathode materials are usually mixed with anode materials to form "black powder" materials. In the context of direct remediation technology, this complex composition presents significant challenges to the direct regeneration of cathode materials. This is especially true for degraded lithium iron phosphate cathode black powder, which usually requires sintering in a reducing atmosphere. The graphite contained within is not burned off during this subsequent sintering process. The presence of carbon materials affects the subsequent remediation process; in particular, a certain amount of graphite reduces the specific capacity of the cathode material in the mixture, making it difficult to restore the performance level of commercial products.

[0005] In the context of battery recycling, the treatment of lithium iron phosphate (LFP) black powder primarily employs hydrometallurgy, extracting the most valuable lithium salts from the black powder for reuse. Further studies have explored wet purification and regeneration of the entire black powder composition; others involve sintering LFP black powder materials in an oxidizing atmosphere to remove carbon materials, yielding iron phosphate; or, after removing carbon materials in an oxidizing atmosphere, adding lithium salts and reducing agents, and then regenerating LFP through reduction roasting. However, while these studies have achieved some degree of regeneration of LFP black powder, they inevitably increase the complexity of the LFP recycling process. Additionally, some studies have used aeration in circulating equipment to recover carbon powder from LFP black powder, but these neglect the direct high-value utilization of the valuable lithium iron phosphate component. At the current laboratory level, direct LFP remediation methods include hydrothermal methods and eutectic flux methods, none of which consider the influence of graphite in the black powder material.

[0006] Therefore, there is an urgent need to provide an effective processing technology to separate the valuable component lithium iron phosphate, modify it, promote the solid-phase lithium replenishment process, and at the same time separate and upgrade graphite for utilization, so as to achieve short-process, low-cost remediation of lithium iron phosphate black powder and full-component recycling of waste battery positive and negative electrode black powder. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for recycling positive and negative electrode black powder from waste batteries, a slurry processing and separation device, and repaired lithium iron phosphate material. The recycling method provided by this invention achieves the separation of lithium iron phosphate material and graphite, the dispersion of agglomerates, and the modification of the lithium iron phosphate material surface. Furthermore, it upgrades graphite into graphene, efficiently recycling both materials and improving large-scale processing efficiency. In addition, by combining it with solid-phase lithium replenishment repair technology, it can achieve efficient and direct repair of the structure and performance of failed lithium iron phosphate, while also broadening the application of graphite-to-graphene upgrades, thereby realizing the full-component processing and resource utilization of positive and negative electrode black powder.

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

[0009] In a first aspect, the present invention provides a method for recycling black powder from the positive and negative electrodes of waste batteries, the recycling method comprising the following steps:

[0010] (1) Mix the positive and negative electrode black powders with a solvent to obtain a positive and negative electrode black powder slurry;

[0011] The positive and negative electrode black powders include lithium iron phosphate black powder particles and graphite;

[0012] (2) The positive and negative electrode black powder slurry is homogenized to obtain homogenized material, and then the positive electrode product and the negative electrode product are separated.

[0013] The homogenized material includes modified lithium iron phosphate particles and graphene.

[0014] The recycling method provided by this invention achieves the separation of lithium iron phosphate materials and graphite, the dispersion of agglomerates, and the modification of the lithium iron phosphate material surface. Furthermore, it upgrades graphite into graphene, efficiently recovering both materials. In addition, combining this method with solid-phase lithium replenishment repair technology enables efficient and direct repair of the structure and performance of failed lithium iron phosphate, while also expanding the application of graphite-to-graphene upgrades. This ultimately achieves the full-component treatment and resource utilization of the black powder from the positive and negative electrodes of spent batteries.

[0015] It should be noted that the lithium iron phosphate (LFP) particles in the black powder from the positive and negative electrodes of used batteries are expired LFP particles. This means that primary particles have agglomerated into secondary particles, the particle surface contains binders and residual lithium salts, and the particles are damaged. Modified LFP particles refer to LFP particles that have undergone surface modification due to collisions, resulting in clean, smooth, and impurity-free particle surfaces with uniform particle size and morphology.

[0016] Preferably, the positive and negative electrode black powder in step (1) also includes a binder.

[0017] Preferably, the solvent includes water.

[0018] Preferably, the solid content of the positive and negative electrode black powder slurry is 5-1000 mg / mL, for example, it can be 10 mg / mL, 50 mg / mL, 100 mg / mL, 300 mg / mL, 500 mg / mL, 700 mg / mL or 1000 mg / mL, etc., and preferably 10-500 mg / mL.

[0019] In this invention, the appropriate solid content of the positive and negative electrode black powder slurry helps to regulate the interface of lithium iron phosphate during the homogenization process, which is beneficial to controlling the efficiency and yield of graphite exfoliation into graphene, and improving the efficiency of black powder treatment and regeneration.

[0020] Preferably, the homogenization process is a sand milling process.

[0021] In this invention, collision homogenization modification is achieved through the mutual collision between the positive and negative electrode black powder slurry and the grinding media. At the same time, the particles collide with each other, causing graphite to be exfoliated and forming graphene.

[0022] Preferably, the linear speed of the grinding is 1-12 m / s, for example, it can be 1 m / s, 3 m / s, 5 m / s, 7 m / s, 9 m / s or 12 m / s, etc.

[0023] Preferably, during the sand milling process, the ratio of positive and negative electrode black powder slurry to the sand milling media is (1-50):(50-1), for example, it can be 1:10, 1:20, 1:30, 1:40, 1:50, 10:1, 10:10, 10:20, 10:30 or 50:10, etc., preferably (1:20-20:1).

[0024] In this invention, a suitable material-to-particle ratio helps to control the size, morphology, and surface properties of lithium iron phosphate particles in black powder, as well as the exfoliation effect of graphene in graphite.

[0025] Preferably, the grinding process takes 0.5-10 hours, for example, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0026] Preferably, the particle size D50 of the modified lithium iron phosphate particles is 1-1000nm, for example, it can be 1nm, 50nm, 100nm, 200nm, 400nm, 600nm, 800nm ​​or 1000nm, etc., and is preferably 200-500nm.

[0027] Preferably, the homogenization process is a self-generated collision homogenization process.

[0028] In this invention, the self-generated collision homogenization process does not involve the addition of grinding media. Instead, it utilizes the characteristics of the particles themselves to regulate the particle movement speed, thereby achieving particle collision, homogenization modification, and separation.

[0029] Preferably, during the self-generated collision homogenization process, the flow rate of the positive and negative electrode black powder slurry is 0.1-800 L / h (liters per hour), for example, it can be 1 L / h, 20 L / h, 50 L / h, 100 L / h, 300 L / h, 500 L / h, 700 L / h or 800 L / h, etc., and preferably 10-100 L / h.

[0030] In this invention, the appropriate flow rate of the positive and negative electrode black powder slurry during the self-generated collision homogenization process helps to regulate the mutual collision behavior of particles in the black powder material, thereby effectively regulating the size, morphology, and surface properties of lithium iron phosphate particles, and improving the exfoliation effect of graphene in graphite.

[0031] In a second aspect, the present invention provides a slurry processing and separation apparatus suitable for the recycling method described in the first aspect, the slurry processing and separation apparatus comprising a homogenization device and a separation device along the direction of slurry flow.

[0032] The homogenization device includes a homogenization processing chamber, with an inlet at one end and an outlet at the other end; the separation device includes a separation chamber, with an inlet, a bottom outlet, and an overflow outlet. The inlet of the separation chamber is connected to the outlet of the homogenization processing chamber. The bottom outlet and the overflow outlet are located at the bottom and top of the separation chamber, respectively, and are used to output positive electrode products and negative electrode products, respectively.

[0033] In this invention, the slurry processing and separation device and the recycling method are flexibly coordinated. The homogenization device and the separation device work together, and multiple homogenization devices or multiple separation devices can work simultaneously, which is beneficial to improving the efficiency of large-scale processing.

[0034] Preferably, the homogenization device is a sand mill.

[0035] In this invention, the sand mill contains grinding media, which disperses the agglomerates of positive and negative electrode black powder slurry and homogenizes lithium iron phosphate particles into nanoparticles. Simultaneously, the surface of the lithium iron phosphate particles is modified due to collisions. Furthermore, the collisions between particles also cause graphite to exfoliate, forming graphene.

[0036] Preferably, the sand mill includes a sand milling chamber, and the chamber wall of the sand milling chamber is provided with a jacket for circulating coolant.

[0037] In this invention, the sand mill has a coolant circulation system, which can accelerate the release of heat generated by the high-speed rotating equipment and the materials colliding with each other, thereby promoting the efficient operation of the equipment.

[0038] Preferably, the coolant is cold water. It should be noted that the temperature of the cold water can be ordinary tap water, and the temperature range can be 5-30℃, such as 25℃.

[0039] Preferably, the grinding chamber is further provided with a coolant inlet and a coolant outlet, which are connected to the interlayer.

[0040] Preferably, the discharge port of the same sand mill corresponds to the feed port of multiple separation devices, or the discharge ports of multiple sand mills correspond to the feed port of the same separation device.

[0041] In this invention, homogenization modification and cyclone classification work synergistically, allowing multiple homogenization modification devices or multiple hydrocyclones to operate simultaneously, which is beneficial for large-scale processing. Furthermore, if at least two sand mills are used, the output material can be collected in a material tank, mixed uniformly, and then pumped into the hydrocyclone. The same principle applies to the following.

[0042] Preferably, the homogenization device is a homogenizer.

[0043] Preferably, the homogenizer includes a homogenizing chamber, a collision ring, and a homogenizing collision valve. The homogenizing chamber and the homogenizing collision valve are connected by the collision ring, and there is a gap between the homogenizing chamber and the homogenizing collision valve to provide a place for particle collision and a channel for material transfer.

[0044] It should be noted that the homogenizer is a collision valve body containing a homogenizing collision valve and a collision ring. When it is working, the material flow is first passed through a flow-limiting gap of a specific width and enters the homogenizing collision valve under high pressure and low flow rate, generating ultra-intense energy. This energy is accompanied by physical and chemical reactions such as collision effect, cavitation effect, and high-speed shear effect, so as to achieve the effect of material homogenization (uniform and micronized distribution of solute particles in solvent). Specifically, it includes the homogenization and modification of lithium iron phosphate, as well as the exfoliation of graphite into graphene.

[0045] Preferably, the discharge port of the same homogenizer corresponds to the inlet of multiple separation devices, or the discharge ports of multiple homogenizers correspond to the inlet of the same separation device.

[0046] Preferably, the separation device is a hydrocyclone.

[0047] In this invention, taking advantage of the low density and hydrophobicity of graphene and the high density of lithium iron phosphate particles, they can be effectively separated in a hydrocyclone based on density, with lighter particles spiraling upwards and heavier particles sinking, thus obtaining separated modified lithium iron phosphate particle cathode products and high-value graphene anode products. The modified lithium iron phosphate can be used for subsequent direct solid-phase lithium replenishment repair, restoring its structure and performance, while the collected graphene can be upgraded for use as carbon materials.

[0048] Preferably, the cyclone separator has a conical structure.

[0049] Preferably, the feed inlet of the homogenization device is used to input positive and negative electrode black powder slurry, and the feed flow rate of the positive and negative electrode black powder slurry is 5-800L / h, for example, it can be 10L / h, 20L / h, 50L / h, 100L / h, 300L / h, 500L / h, 700L / h or 800L / h, etc., preferably 10-100L / h, etc.

[0050] In this invention, a suitable feed flow rate helps to control the separation effect of graphene and lithium iron phosphate particles.

[0051] Preferably, the discharge port of the homogenizing device is used to output homogenized material, and the discharge flow rate of the homogenized material is 5-800L / h, for example, it can be 10L / h, 50L / h, 100L / h, 300L / h, 500L / h, 700L / h or 800L / h, etc., preferably 5-100L / h, etc.

[0052] In this invention, a suitable discharge flow rate helps to improve the yield of lithium iron phosphate products.

[0053] Thirdly, the present invention provides a repaired lithium iron phosphate material, wherein the repaired lithium iron phosphate material is obtained by solid-phase co-firing of the cathode product recovered by the recycling method described in the first aspect with a lithium replenishing agent and a reducing agent.

[0054] Fourthly, the present invention provides a method for repairing lithium iron phosphate materials after repair, the method comprising the following steps:

[0055] The positive electrode product, lithium replenishing agent, and reducing agent are mixed and solid-state sintered in an inert atmosphere to obtain the repaired lithium iron phosphate material.

[0056] Preferably, the lithium supplement comprises a lithium salt. Examples include LiOH or Li₂CO₃.

[0057] Preferably, the reducing agent includes PVP (polyvinylpyrrolidone) and / or amino acids.

[0058] Preferably, the mass ratio of the positive electrode product, lithium replenishing agent, and reducing agent is 1:(0.05-1.2):(0.01-2), wherein the lithium replenishing agent is selected in the range of "0.05-1.2", for example, 0.05, 0.1, 0.5, 1, or 1.2, and the reducing agent is selected in the range of "0.01-2", for example, 0.01, 0.05, 0.1, 0.5, 1, 1.5, or 2, etc.

[0059] Preferably, the solid-state sintering is a one-step sintering or a multi-step sintering.

[0060] Preferably, the sintering temperature of the one-step sintering is 300-700℃, for example, 300℃, 400℃, 500℃, 600℃ or 700℃, and the time is 0.1-5h, for example, 0.1h, 0.5h, 1h, 2h, 3h, 4h or 5h.

[0061] Preferably, the stepwise sintering includes a first-stage sintering and a second-stage sintering. The temperature of the first-stage sintering is 300-500℃, for example, 300℃, 340℃, 380℃, 420℃, 460℃, or 500℃, and the time is 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. The temperature of the second-stage sintering is 600-700℃, for example, 600℃, 620℃, 640℃, 660℃, 680℃, or 700℃, and the time is 0.5-1.5 hours, for example, 0.5 hours, 1 hour, or 1.5 hours.

[0062] Preferably, the heating rate of the solid-state sintering is 0.5-10℃ / min, for example, it can be 0.5℃ / min, 1℃ / min, 3℃ / min, 2℃ / min, 7℃ / min, 8℃ / min or 10℃ / min, etc.

[0063] Fifthly, the present invention provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery comprises the positive electrode product as described in the first aspect, or comprises the repaired lithium iron phosphate material as described in the third aspect.

[0064] 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.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] The recycling method provided by this invention achieves the separation of lithium iron phosphate materials and graphite, the dispersion of agglomerates, and the modification of the lithium iron phosphate material surface. Furthermore, it upgrades graphite into graphene. This recycling method is flexible in its integration with slurry processing and separation devices; the homogenization and separation devices work synergistically, allowing multiple homogenization or separation devices to operate simultaneously, which improves the efficiency of large-scale processing. In addition, combining this method with solid-phase lithium replenishment repair technology enables efficient and direct repair of the structure and performance of failed lithium iron phosphate, while also expanding the application of graphite-to-graphene upgrades, thereby achieving full-component processing and resource utilization of both positive and negative electrode black powders. Attached Figure Description

[0067] Figure 1 This is a process diagram of the sand mill and hydrocyclone provided in Embodiment 1 of the present invention.

[0068] Figure 2 This is a process diagram of the homogenizer and hydrocyclone provided in Embodiment 2 of the present invention.

[0069] Figure 3 This is a SEM image of the positive and negative electrode black powder in Application Example 1 of the present invention.

[0070] Figure 4 This is a SEM image of the modified lithium iron phosphate particle product in Application Example 1 of the present invention.

[0071] Figure 5 This is a low-magnification SEM image of graphene homogenized from the positive and negative electrode black powders after separation. (Example 1 of this invention)

[0072] Figure 6 This is a high-magnification SEM image of graphene homogenized from the positive and negative electrode black powder after separation in Application Example 1 of this invention.

[0073] Figure 7 The comparison curves of the cycle performance of the positive and negative electrode black powder and the repaired lithium iron phosphate material provided in Application Example 1 of the present invention are shown.

[0074] Figure 8 The capacity-voltage comparison curves of the positive and negative electrode black powder and the repaired lithium iron phosphate material provided in Application Example 1 of the present invention are shown.

[0075] Among them, 1-sand mill; 11-feed inlet; 12-discharge outlet; 13-sand mill chamber; 14-cold water inlet; 15-cold water outlet; 16-jacket; 17-cooling cover plate; 18-rotor; 2-cyclone separator; 21-cyclone feed inlet; 22-overflow outlet; 23-underflow outlet; 1'-homogenizer; 11'-homogenization chamber; 12'-collision ring; 13'-homogenization collision valve. Detailed Implementation

[0076] 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 in any way.

[0077] It should be noted that the positive and negative electrode black powders used in the following examples and comparative examples are positive and negative electrode black powders with the same composition, wherein the mass content of lithium iron phosphate black powder particles is 80wt%, the mass content of graphite is 15wt%, and the binder includes carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), with a mass content of 5wt%.

[0078] Example 1

[0079] This embodiment provides a slurry processing and separation device, such as... Figure 1 As shown, the slurry processing and separation device includes a sand mill 1 and a hydrocyclone 2 along the direction of slurry flow.

[0080] The sand mill 1 includes a sand milling chamber 13, with a feed inlet 11 at one end and a discharge outlet 12 at the other end, the discharge outlet 12 being located on the cooling cover plate 17; a jacket 16 is provided in the cavity wall of the sand milling chamber 13 for circulating coolant; the sand milling chamber 13 is also provided with a cold water inlet 14 and a cold water outlet 15, which are connected to the jacket 16; the sand milling chamber 13 contains sand milling media (rotor 18).

[0081] The hydrocyclone 2 includes a hydrocyclone separation chamber, which is conical in shape. The hydrocyclone separation chamber is provided with a hydrocyclone inlet 21, an underflow outlet 23, and an overflow outlet 22. The hydrocyclone inlet 21 is connected to the outlet 12 of the sand mill 1. The underflow outlet 23 and the overflow outlet 22 are located at the bottom and top of the hydrocyclone separation chamber, respectively, and are used to output modified lithium iron phosphate particle products and graphene products, respectively.

[0082] Example 2

[0083] This embodiment provides a slurry processing and separation device, such as... Figure 2 As shown, the slurry processing and separation device includes a homogenizer 1' and a hydrocyclone 2 along the direction of slurry flow.

[0084] The homogenizer 1' includes a homogenization chamber 11', a collision ring 12', and a homogenization collision valve 13'. The homogenization chamber 11' and the homogenization collision valve 13' are connected by the collision ring 12', and there is a gap between the homogenization chamber 11' and the homogenization collision valve 13' to provide a space for particle collision and material transfer.

[0085] The hydrocyclone 2 includes a cyclone separation chamber, which is conical in shape. The cyclone separation chamber is provided with a cyclone inlet 21, an underflow outlet 23, and an overflow outlet 22. The cyclone inlet 21 is connected to the outlet of the homogenizer 1'. The underflow outlet 23 and the overflow outlet 22 are located at the bottom and top of the cyclone separation chamber, respectively, and are used to output modified lithium iron phosphate particle products and graphene products, respectively.

[0086] Application Example 1

[0087] This application example provides a method for recycling the black powder from the positive and negative electrodes of waste batteries. The recycling method uses the slurry processing and separation device provided in Example 1 above, and the specific steps include:

[0088] (1) Mix the positive and negative electrode black powder with water to obtain a positive and negative electrode black powder slurry with a solid content of 50 mg / mL.

[0089] The positive and negative electrode black powders include lithium iron phosphate black powder particles, binder, and graphite.

[0090] (2) The positive and negative electrode black powder slurry is fed into the sand mill at a feed flow rate of 20L / h to homogenize the lithium iron phosphate black powder particles (i.e., the sand milling process), and at the same time, the graphite is exfoliated to obtain modified lithium iron phosphate particles and graphene with a particle size D50 of 200nm.

[0091] (3) The modified lithium iron phosphate particles and graphene in the sand mill are output to the hydrocyclone at a discharge flow rate of 30L / h to separate the modified lithium iron phosphate particle product and the graphene product.

[0092] The ratio of positive and negative electrode black powder slurry to rotor in the sand mill is 1:10, the rotation speed of the sand mill is 5m / s, and the sand milling time is 1h.

[0093] This embodiment also provides a repaired lithium iron phosphate material, which is obtained by solid-phase co-firing of modified lithium iron phosphate particles recovered by the above-described recycling method with a lithium replenishing agent and a reducing agent.

[0094] This embodiment also provides a method for repairing the above-mentioned repaired lithium iron phosphate material, the repair method including the following steps:

[0095] Modified lithium iron phosphate particles, LiOH, and PVP were mixed and heated to 500°C at a heating rate of 5°C / min in a nitrogen atmosphere, and then subjected to isothermal solid-state sintering for 2.5 hours to obtain the repaired lithium iron phosphate material.

[0096] The mass ratio of modified lithium iron phosphate particles, LiOH, and PVP is 1:0.2:0.05.

[0097] Figure 3 and Figure 4 SEM images of the positive and negative electrode black powder and the modified lithium iron phosphate particle product in this embodiment are shown. As can be seen from the images, the positive and negative electrode black powder from the waste battery contains a large number of graphite particles, and the lithium iron phosphate particles show agglomeration. In contrast, the modified lithium iron phosphate particle product has a smooth surface and uniform particle size and morphology. Furthermore, no graphite was observed in the lithium iron phosphate material after homogenization treatment, indicating that the graphite was effectively separated.

[0098] Figure 5 and Figure 6 Low-magnification and high-magnification SEM images of graphite homogenization after separation of positive and negative electrode black powder in this embodiment are shown respectively. As can be seen from the figures, the homogenization process can effectively reduce the size and thickness of graphite, achieving the standard for graphene. In particular, the hydrocyclone can effectively separate graphene products with lower density.

[0099] Figure 7 and Figure 8 The cycle performance comparison curves and capacity-voltage comparison curves of the positive and negative electrode black powder and the repaired lithium iron phosphate material provided in this embodiment are shown respectively. Figure 7It can be seen that under 1C charge-discharge conditions, the initial capacity of the black powder was 108 mAh / g; it quickly dropped below 70 mAh / g in the third cycle; and after 50 charge-discharge cycles, only 37% was retained. In contrast, the initial capacity of the repaired lithium iron phosphate material reached 140 mAh / g, reaching commercial levels; after the first 50 charge-discharge cycles, the capacity hardly decayed; and after 100 cycles, it still retained 91% of its capacity, demonstrating good cycle stability. Figure 8 The difference in specific capacity between the two can be seen intuitively; the repaired lithium iron phosphate material exhibits less polarization.

[0100] Application Example 2

[0101] This application example provides a method for recycling black powder from the positive and negative electrodes of waste batteries. The recycling method uses the slurry processing and separation device provided in Example 2 above, and the specific steps include:

[0102] (1) Mix the positive and negative electrode black powder with water to obtain a positive and negative electrode black powder slurry with a solid content of 50 mg / mL.

[0103] The positive and negative electrode black powders include lithium iron phosphate black powder particles, binder, and graphite.

[0104] (2) The positive and negative electrode black powder slurry is fed into the homogenizer at a feed rate of 20L / h to homogenize the lithium iron phosphate black powder particles (i.e., self-generated collision homogenization process), and the graphite is exfoliated to obtain modified lithium iron phosphate particles and graphene with a particle size D50 of 200nm.

[0105] (3) The modified lithium iron phosphate particles and graphene in the homogenizer are output to the hydrocyclone at a discharge flow rate of 30L / h to separate the modified lithium iron phosphate particle product and the graphene product.

[0106] In the homogenizer, the flow rate of the positive and negative electrode black powder slurry is 30L / h.

[0107] This embodiment also provides a repaired lithium iron phosphate material, which is obtained by solid-phase co-firing of modified lithium iron phosphate particles recovered by the above-described recycling method with a lithium replenishing agent and a reducing agent.

[0108] This embodiment also provides a method for repairing the above-mentioned repaired lithium iron phosphate material, the repair method including the following steps:

[0109] The modified lithium iron phosphate particles, Li2CO3, and amino acids were mixed and heated to 700°C at a heating rate of 7°C / min in a nitrogen atmosphere, and then subjected to isothermal solid-state sintering for 3 hours to obtain the repaired lithium iron phosphate material.

[0110] The mass ratio of modified lithium iron phosphate particles, Li2CO3, and amino acids is 1:0.1:0.2.

[0111] Application Example 3

[0112] The difference between this embodiment and embodiment 1 is that the solid content of the positive and negative electrode black powder slurry in step (1) is 5 mg / mL.

[0113] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0114] Application Example 4

[0115] The difference between this application example and application example 1 is that the solid content of the positive and negative electrode black powder slurry in step (1) is 1000 mg / mL.

[0116] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0117] Application Example 5

[0118] The difference between this application example and application example 1 is that the feed flow rate of the positive and negative electrode black powder slurry into the sand mill in step (2) is 5L / h.

[0119] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0120] Application Example 6

[0121] The difference between this application example and application example 1 is that the feed flow rate of the positive and negative electrode black powder slurry into the sand mill in step (2) is 800L / h.

[0122] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0123] Application Example 7

[0124] The difference between this application example and application example 1 is that the discharge flow rate of the modified lithium iron phosphate particles and graphene in step (3) is 5L / h.

[0125] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0126] Application Example 8

[0127] The difference between this application example and application example 1 is that the discharge flow rate of the modified lithium iron phosphate particles and graphene in step (3) is 800 L / h.

[0128] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0129] Application Example 9

[0130] The difference between this application example and application example 1 is that the ratio of positive and negative electrode black powder slurry to grinding media in the sand mill is 50:1.

[0131] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0132] Application Example 10

[0133] The difference between this application example and application example 1 is that the ratio of positive and negative electrode black powder slurry to grinding media in the sand mill is 1:50.

[0134] The remaining recycling methods and parameters are consistent with those in Application Example 1.

[0135] Application Example 11

[0136] The difference between this application example and application example 2 is that the flow rate of the positive and negative electrode black powder slurry in the homogenizer is 0.1 L / h.

[0137] The remaining recycling methods and parameters are consistent with those in Application Example 2.

[0138] Application Example 12

[0139] The difference between this application example and application example 2 is that the flow rate of the positive and negative electrode black powder slurry in the homogenizer is 800 L / h.

[0140] The remaining recycling methods and parameters are consistent with those in Application Example 2.

[0141] Application Comparative Example 1

[0142] This application provides a comparative example of a method for recycling black powder from the positive and negative electrodes of waste batteries. The recycling method includes the following steps:

[0143] (1) Place the black powder of positive and negative electrodes of waste batteries in a fixed bed reactor. The heat treatment atmosphere is argon gas. The heat treatment temperature is set to 600℃, the flow rate of water is 20mL / h, and the reaction time is 1.5 hours. The product gas and solid are obtained by gas-solid separation.

[0144] (2) The product gas is collected and utilized as clean synthesis gas after condensation, drying and dust removal. The collected product gas is mainly hydrogen, carbon monoxide, methane and carbon dioxide.

[0145] (3) The collected solid is lithium iron phosphate powder without carbon impurities.

[0146] Performance testing

[0147] The repaired lithium iron phosphate materials provided in Application Examples 1-12 and Comparative Example 1 of this invention were respectively used to prepare lithium-ion batteries. The specific steps included:

[0148] The repaired lithium iron phosphate material was mixed with conductive carbon black and binder at a mass ratio of 8:1:1, and a uniform slurry was obtained using a homogenizer. This slurry was then dripped onto carbon-coated aluminum foil and coated using a doctor blade. The slurry was subsequently dried in a forced-air drying oven at 80°C for 6 hours. It was then cut into 13mm diameter positive electrode sheets. These positive electrode sheets were further dried in a vacuum oven at 120°C for 4 hours to obtain the prepared positive electrode sheet. Finally, the positive electrode sheet was transferred to a glove box for battery assembly.

[0149] The assembly process includes selecting a lithium sheet as the counter electrode, combining it with a PP separator, and assembling it into a coin cell by stacking layers. Specifically, 100 μL of electrolyte is added. The electrolyte is a mixed solution containing 1M lithium hexafluorophosphate (LiPF6), and the solvent includes ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1.

[0150] The electrochemical performance of the battery prepared above was tested under the following conditions: charge and discharge test at 1C rate.

[0151] The test results are shown in Table 1.

[0152] Table 1

[0153]

[0154] analyze:

[0155] As can be seen from Application Examples 1 and 3-4, if the solid content of the positive and negative electrode black powder slurry in step (1) is small, the slurry is very thin, the particles collide unevenly, the homogenization effect is not good, and the electrochemical performance is poor; if the solid content of the positive and negative electrode black powder slurry in step (1) is large, the slurry concentration is too large, the separation effect is not good, and the final lithium iron phosphate product still contains a small amount of graphite, which affects the capacity.

[0156] As can be seen from Application Examples 1 and 5-6, if the feed rate of the positive and negative electrode black powder slurry into the sand mill in step (2) is small, precipitation is likely to occur in the chamber, resulting in poor homogenization and affecting the surface modification of lithium iron phosphate material; if the feed rate of the positive and negative electrode black powder slurry into the sand mill in step (2) is large, the grinding is insufficient, resulting in the hydrocyclone being unable to completely separate the particles, and the underflow product still contains graphite, reducing the specific capacity.

[0157] As can be seen from Application Examples 1 and 7-8, if the discharge rate of modified lithium iron phosphate particles and graphene in step (3) is small, some graphene will covalently stack in the hydrocyclone, causing sedimentation and entering the bottom flow lithium iron phosphate, reducing the separation efficiency. The entrained graphene affects the capacity of lithium iron phosphate. If the discharge rate of modified lithium iron phosphate particles and graphene in step (3) is large, the material transport is too fast, and there is a problem that lithium iron phosphate and graphene cannot be separated in time. The entrained graphene affects the capacity.

[0158] As can be seen from Application Examples 1 and 9-10, if the positive and negative electrode black powder slurry and the grinding media balls in the sand mill are relatively small, the grinding will be insufficient, the homogenization effect will be poor, and the modification of the lithium iron phosphate interface and the graphite exfoliation of graphene will not be achieved, thus affecting the capacity of the repaired product. If the positive and negative electrode black powder slurry and the grinding media balls in the sand mill are relatively large, the particle fineness will be affected, the surface modification of the lithium iron phosphate particles will be affected, and the subsequent lithium supplementation sintering will have inconsistent structural repair problems, which will lead to a decrease in specific capacity.

[0159] As can be seen from Application Examples 1 and 11-12, if the flow rate of the positive and negative electrode black powder slurry in the homogenizer is relatively low, the self-collision between particles is weak, resulting in poor homogenization effect, affecting the surface modification of lithium iron phosphate, and causing incomplete recovery of electrochemical performance; if the flow rate of the positive and negative electrode black powder slurry in the homogenizer is relatively high, the material flow is too fast, resulting in poor homogenization effect, directly affecting the homogenization modification and separation process, resulting in poor product performance.

[0160] As can be seen from Application Example 1 and Comparative Application Example 1, compared with the recycling methods used in the prior art, this application can better restore the structure and performance of lithium iron phosphate. This is mainly because the homogenization process modifies the surface of the spent lithium iron phosphate, which is beneficial to the lithium replenishment process. At the same time, the graphite in the black powder is separated. The separation process does not involve oxidative heating conditions and will not damage the surface interface of the lithium iron phosphate.

[0161] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling black powder from the positive and negative electrodes of waste batteries, characterized in that, The recycling method includes the following steps: (1) Mix the positive and negative electrode black powder of waste batteries with solvent to obtain positive and negative electrode black powder slurry; The waste battery positive and negative electrode black powder includes lithium iron phosphate black powder particles and graphite; the solvent includes water; The solid content of the positive and negative electrode black powder slurry is 5-50 mg / mL; (2) The positive and negative electrode black powder slurry is homogenized and homogenized material is obtained through material collision. Then, the modified lithium iron phosphate particle product and graphene product are separated according to the density difference. The homogenization process is either a sand milling process or a self-generated collision homogenization process; during the sand milling process, the ratio of positive and negative electrode black powder slurry to the sand milling media is (1-20):(20-1); during the self-generated collision homogenization process, the flow rate of the positive and negative electrode black powder slurry is 10-100 L / h; the homogenized material includes modified lithium iron phosphate particles and graphene. A slurry processing and separation apparatus suitable for the aforementioned recycling method, the slurry processing and separation apparatus comprising a homogenization device and a separation device along the direction of slurry flow; The homogenization device includes a homogenization processing chamber, with a feed inlet at one end and a discharge outlet at the other end; the separation device includes a separation chamber, with a feed inlet, an underflow outlet, and an overflow outlet. The feed inlet of the separation chamber is connected to the discharge outlet of the homogenization processing chamber. The underflow outlet and the overflow outlet are located at the bottom and top of the separation chamber, respectively, and are used to output modified lithium iron phosphate particle products and graphene products, respectively. The homogenization device is a sand mill or a homogenizer; the sand mill includes a sand milling chamber, the chamber wall of which is provided with a jacket for circulating coolant; the homogenizer includes a homogenization chamber, a collision ring, and a homogenization collision valve, the homogenization chamber and the homogenization collision valve are connected by the collision ring, and there is a gap between the homogenization chamber and the homogenization collision valve to provide a place for particle collision and a channel for material transport; the feed port of the homogenization device is used to input positive and negative electrode black powder slurry, and the feed flow rate of the positive and negative electrode black powder slurry is 10-100 L / h; the discharge port of the homogenization device is used to output homogenized material, and the discharge flow rate of the homogenized material is 10-100 L / h.

2. The recycling method according to claim 1, characterized in that, The positive and negative electrode black powders in step (1) also include a binder.

3. The recycling method according to claim 1, characterized in that, The linear velocity during the grinding process is 1-12 m / s; The grinding process takes 0.5-10 hours. And / or, the particle size D50 of the modified lithium iron phosphate particles is 1-1000 nm.

4. The recycling method according to claim 1, characterized in that, The grinding chamber is also provided with a coolant inlet and a coolant outlet, which are connected to the interlayer; The discharge port of the same sand mill corresponds to the inlet of multiple separation devices, or the discharge ports of multiple sand mills correspond to the inlet of the same separation device.

5. The recycling method according to claim 1, characterized in that, The discharge port of the same homogenizer corresponds to the inlet of multiple separation devices, or the discharge ports of multiple homogenizers correspond to the inlet of the same separation device.

6. The recycling method according to claim 1, characterized in that, The separation device is a hydrocyclone; The hydrocyclone has a conical structure.

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