Method for recovering black powder of positive and negative electrodes of waste batteries, slurry processing and separating device and repaired lithium iron phosphate material

Abstract

The invention provides a waste battery positive and negative electrode black powder recovery method, a slurry processing and separating device and a repaired lithium iron phosphate material, and belongs to the technical field of waste battery recovery and reutilization. The recovery method comprises the following steps: mixing anode and cathode black powder with a solvent to obtain anode and cathode black powder slurry; wherein the anode and cathode black powder comprises lithium iron phosphate black powder particles and graphite; homogenizing the positive and negative electrode black powder slurry to obtain a homogenized material, and then separating to obtain a positive electrode product and a negative electrode product; wherein the homogenized material comprises modified lithium iron phosphate particles and graphene. According to the recovery method, the separation of the lithium iron phosphate material and the graphite, the dispersion of the aggregate and the surface modification of the lithium iron phosphate material are realized, and the graphite is converted into the graphene. In addition, the recycling method is flexibly matched with a slurry processing and separating device, and the large-scale treatment efficiency can be improved. In addition, efficient and direct repair of the structure and performance of the failed lithium iron phosphate can be realized by combining a solid-phase lithium supplement repair technology.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and reusing waste batteries, and specifically relates to a method for recycling positive and negative black powder of waste batteries, a slurry processing and separation device, and a repaired lithium iron phosphate material. Background Art

[0002] With the continuous expansion of the new energy vehicle market and the increasing number of cars, 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 year by year. If these large amounts of waste batteries are not properly disposed of, it will not only pose a serious threat to the environment, but also lead to a huge waste of resources. Therefore, it has become a top priority to establish an effective waste power battery recycling system and promote the reuse of its resources.

[0003] There are three main ways to recycle and reuse spent lithium-ion batteries: pyrometallurgy, hydrometallurgy, and direct regeneration. Among them, pyrometallurgy and hydrometallurgy have the advantage of mature technology, but usually have long treatment cycles and complex wastewater and waste gas treatment processes, resulting in high costs. Direct regeneration is a repair method developed based on lithium replenishment technology, which has the characteristics of short regeneration process, less pollution emissions, and low energy consumption costs, and has broad application prospects.

[0004] However, existing methods for processing large amounts of waste batteries usually obtain valuable components after direct crushing, screening and sorting. Positive electrode materials with higher economic value are usually mixed with negative electrode materials to form "black powder" materials. In the technical background of direct repair, the complex component composition makes the direct regeneration of positive electrode materials face great challenges. In particular, for failed lithium iron phosphate positive electrode black powder, a reducing atmosphere is usually required for sintering. The graphite contained will not be burned during the subsequent sintering process. The presence of carbon materials will affect the subsequent repair process, especially a certain content of graphite will reduce the specific capacity of the positive electrode 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 black powder mainly adopts hydrometallurgy, and the lithium salt with the highest value in the black powder is extracted by lithium extraction for reuse. Furthermore, some studies have wet-purified and recycled all components of black powder; some studies have sintered lithium iron phosphate black powder materials in an oxidizing atmosphere to remove carbon materials and obtain iron phosphate; or after removing carbon materials in an oxidizing atmosphere, lithium salts and reducing agents are further added to obtain lithium iron phosphate through reduction roasting and lithium supplementation. However, although the above studies have recycled lithium iron phosphate black powder to a certain extent, the process of lithium iron phosphate recycling and regeneration is inevitably increased. In addition, there are also studies that realize the recycling of carbon powder in lithium iron phosphate black powder through aeration of circulating equipment, but ignore the direct high-value utilization of the valuable component lithium iron phosphate. At the existing laboratory level, direct repair methods for lithium iron phosphate include hydrothermal method, low eutectic method, etc., none of which consider the influence of graphite in black powder materials.

[0006] Therefore, there is an urgent need to provide an effective processing technology to separate the valuable component lithium iron phosphate and modify it to promote the solid-phase lithium replenishment process, while separating the graphite and upgrading it to achieve short-process, low-cost repair of lithium iron phosphate black powder and full component recycling of positive and negative black powder of waste batteries. Summary of the invention

[0007] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a method for recycling the black powder of the positive and negative electrodes of waste batteries, a slurry processing and separation device, and a repaired lithium iron phosphate material. The recycling method provided by the present invention realizes the separation of lithium iron phosphate material and graphite, the dispersion of agglomerates, and the modification of the surface of lithium iron phosphate material on the one hand, and upgrades the graphite to graphene on the other hand, and efficiently realizes the recycling of the two, which is conducive to improving the efficiency of large-scale processing. In addition, further combining the solid-phase lithium supplementation repair technology can realize efficient and direct repair of the structure and performance of failed lithium iron phosphate, while broadening the application of graphite upgrading graphene, thereby realizing the full component processing and resource utilization of positive and negative electrode black powder.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

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

[0010] (1) Mixing positive and negative electrode black powders and a solvent to obtain positive and negative electrode black powder slurries;

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

[0012] (2) homogenizing the positive and negative electrode black powder slurries to obtain a homogenized material, and then separating the positive electrode product and the negative electrode product;

[0013] Wherein, the homogenized material includes modified lithium iron phosphate particles and graphene.

[0014] The recycling method provided by the present invention realizes the separation of lithium iron phosphate material and graphite, the dispersion of agglomerates and the modification of the surface of lithium iron phosphate material on the one hand, and upgrades graphite into graphene on the other hand, and efficiently realizes the recycling of the two. In addition, further combining the solid phase lithium supplementation repair technology can realize the efficient direct repair of the structure and performance of failed lithium iron phosphate, while broadening the application of graphite upgrading graphene, thereby realizing the full component treatment and resource utilization of the positive and negative black powder of waste batteries.

[0015] It should be noted that the lithium iron phosphate black powder particles in the positive and negative black powder of used batteries are expired lithium iron phosphate, which means that the primary particles are agglomerated into secondary particles, the particle surface contains binders and residual lithium salts, and the particles are damaged. Modified lithium iron phosphate particles refer to lithium iron phosphate particles that have undergone surface modification due to collision, making the particle surface clean, free of impurities, smooth, and uniform in size and morphology.

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

[0017] Preferably, the solvent comprises 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., preferably 10-500 mg / mL.

[0019] In the present invention, the positive and negative electrode black powder slurry with appropriate solid content is helpful to regulate the surface interface of lithium iron phosphate during the homogenization process, which is beneficial to control the efficiency and yield of graphite exfoliation into graphene, and is beneficial to improve the black powder processing and regeneration efficiency.

[0020] Preferably, the homogenization process is a sanding process.

[0021] In the present invention, collision homogenization modification is performed by mutual collision between the positive and negative electrode black powder slurry and the sand milling medium, and at the same time, the particles collide with each other, causing the graphite to be peeled off to form graphene.

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

[0023] Preferably, during the sand milling process, the ball ratio of the positive and negative electrode black powder slurry and the sand milling medium 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 the present invention, a suitable material-to-ball ratio helps to regulate the size, morphology, and surface properties of lithium iron phosphate particles in black powder and the exfoliation effect of graphene in graphite.

[0025] Preferably, the sanding process lasts for 0.5-10 h, for example, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h.

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

[0027] Preferably, the homogenization process is an autogenous collision homogenization process.

[0028] In the present invention, the self-generated collision homogenization process does not add sand milling media, but utilizes the characteristics of the particles themselves to control the particle movement speed, thereby achieving particle collision, homogenization modification and separation.

[0029] Preferably, during the autogenous collision homogenization process, the flow rate of the positive and negative electrode black powder slurry is 0.1-800 L / h (liters / 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., preferably 10-100 L / h, etc.

[0030] In the present 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 the 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 device suitable for the recovery method described in the first aspect, wherein the slurry processing and separation device includes a homogenization device and a separation device along the direction of slurry flow.

[0032] The homogenization device comprises a homogenization processing chamber, one end of which is provided with a feed port, and the other end of which is provided with a discharge port; the separation device comprises a separation chamber, the separation chamber is provided with a feed port, an underflow port and an overflow port, the feed port on the separation chamber is connected to the discharge port of the homogenization processing chamber, the underflow port and the overflow port are respectively located at the bottom and top of the separation chamber, and are respectively used to output positive electrode products and negative electrode products.

[0033] In the present invention, the slurry processing and separation device cooperates flexibly with the recovery method, and the homogenization device and the separation device work in coordination, so that multiple homogenization devices or multiple separation devices can work simultaneously, which is beneficial to improving the scale processing efficiency.

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

[0035] In the present invention, the sand mill has grinding media, which can disperse the agglomerates of the positive and negative electrode black powder slurry and homogenize the lithium iron phosphate particles into nanoparticles. At the same time, the surface of the lithium iron phosphate particles is also modified due to collision. In addition, the collision between the particles also causes the graphite to peel off and form graphene.

[0036] Preferably, the sand mill comprises a sand mill cavity, and a sandwich layer is arranged in the cavity wall of the sand mill cavity for circulating cooling liquid.

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

[0038] Preferably, the cooling liquid is cold water. It should be noted that the temperature of the cold water can be regular tap water, and the temperature range can be 5-30°C, such as 25°C.

[0039] Preferably, the sanding cavity is further provided with a cooling liquid inlet and a cooling liquid outlet, which are communicated with the interlayer.

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

[0041] In the present invention, homogenization modification and cyclone classification work together, and multiple homogenization modification devices or multiple cyclones can work simultaneously, which is conducive to large-scale processing. In addition, if at least two sand mills are used, the output materials can be collected in the material barrel and mixed evenly, and then uniformly pumped into the cyclone. The same applies to the following.

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

[0043] Preferably, the homogenizer comprises a homogenizing chamber, a collision ring and a homogenizing collision valve, the homogenizing chamber and the homogenizing collision valve are connected via the collision ring, and there is a gap between the homogenizing chamber and the homogenizing collision valve for providing a place for particle collision and a channel for material transmission.

[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 into the homogenizing collision valve in a state of high pressure and low flow rate, generating ultra-violent energy. This energy is accompanied by physical and chemical reactions such as collision effect, cavitation effect, and high-speed shear effect, thereby achieving the effect of homogenizing the material (solute particles are evenly and micronized in the solvent), specifically including the homogenization and modification of lithium iron phosphate, and the exfoliation of graphite into graphene.

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

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

[0047] In the present invention, based on the characteristics of low density and hydrophobicity of graphene and high density of lithium iron phosphate particles, they can be effectively separated according to density in the cyclone, with the light ones spinning upward and the heavy ones sinking downward, thereby obtaining separated modified lithium iron phosphate particle positive electrode products and high-value graphene negative electrode products. Among them, the modified lithium iron phosphate can be used for subsequent direct solid-phase lithium supplementation and repair to achieve structural and performance recovery, and the collected graphene can be upgraded to be used as carbon materials.

[0048] Preferably, the cyclone is a conical structure.

[0049] Preferably, the feed port in 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 the present invention, a suitable feed flow rate is helpful to regulate the separation effect of graphene and lithium iron phosphate particles.

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

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

[0053] In a third aspect, the present invention provides a repaired lithium iron phosphate material, wherein the repaired lithium iron phosphate material is obtained by solid-phase co-firing a positive electrode product recovered by the recovery method described in the first aspect with a lithium supplement agent and a reducing agent.

[0054] In a fourth aspect, the present invention provides a method for repairing a repaired lithium iron phosphate material, the repair method comprising the following steps:

[0055] The positive electrode product, the lithium supplement agent and the reducing agent are mixed, and solid-phase sintering is performed in an inert atmosphere to obtain the repaired lithium iron phosphate material.

[0056] Preferably, the lithium supplement comprises a lithium salt, for example, LiOH or Li2CO3.

[0057] Preferably, the reducing agent comprises PVP (polyvinyl pyrrolidone) and / or amino acid.

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

[0059] Preferably, the solid phase sintering is one-step sintering or step-by-step sintering.

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

[0061] Preferably, the step-by-step sintering includes one-stage sintering and two-stage sintering, the temperature of the one-stage sintering is 300-500°C, for example, it can be 300°C, 340°C, 380°C, 420°C, 460°C or 500°C, and the time is 1-3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, etc.; the temperature of the two-stage sintering is 600-700°C, for example, it can be 600°C, 620°C, 640°C, 660°C, 680°C or 700°C, etc., and the time is 0.5-1.5h, for example, it can be 0.5h, 1h or 1.5h, etc.

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

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

[0064] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

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

[0066] The recovery method provided by the present invention realizes the separation of lithium iron phosphate material and graphite, the dispersion of agglomerates and the modification of the surface of lithium iron phosphate material on the one hand, and upgrades graphite to graphene on the other hand. In addition, the recovery method is flexible with the slurry processing and separation device, and the homogenization device and the separation device work together, so that multiple homogenization devices or multiple separation devices can work at the same time, which is conducive to improving the efficiency of large-scale processing. In addition, further combining the solid-phase lithium supplementation repair technology can realize efficient and direct repair of the structure and performance of failed lithium iron phosphate, and at the same time broaden the application of graphite upgrading graphene, thereby realizing the full component processing and resource utilization of positive and negative electrode black powder. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0068] Figure 2 This is a process schematic diagram of the homogenizer and cyclone provided in Example 2 of the present invention.

[0069] Figure 3 This is the 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 graphite homogenized into graphene after the positive and negative electrode black powders are separated in Application Example 1 of the present invention.

[0072] Figure 6 This is a high-magnification SEM image of graphite homogenized into graphene after the positive and negative electrode black powders are separated in Application Example 1 of the present invention.

[0073] Figure 7 This is a comparison curve 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.

[0074] Figure 8 This is a capacity-voltage comparison curve of the positive and negative electrode black powder and the repaired lithium iron phosphate material provided in Application Example 1 of the present invention.

[0075] Among them, 1-sand mill; 11-feed port; 12-discharge port; 13-sand mill chamber; 14-cold water inlet; 15-cold water outlet; 16-interlayer; 17-cooling cover plate; 18-rotor; 2-cyclone; 21-cyclone feed port; 22-overflow port; 23-bottom flow port; 1'-homogenizer; 11'-homogenizing chamber; 12'-collision ring; 13'-homogenizing collision valve. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0077] It should be noted that the positive and negative electrode black powders used in the following embodiments and comparative examples are positive and negative electrode black powders of the same components, 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 cyclone 2 along the direction of slurry flow.

[0080] The sand mill 1 comprises a sand mill cavity 13, one end of the sand mill cavity 13 is provided with a feed port 11, the other end is provided with a discharge port 12, and the discharge port 12 is located on the cooling cover plate 17; a sandwich layer 16 is provided in the cavity wall of the sand mill cavity 13 for circulating cooling liquid; the sand mill cavity 13 is also provided with a cold water inlet 14 and a cold water outlet 15, which are connected to the sandwich layer 16; the sand mill cavity 13 contains a sand mill medium (rotor 18).

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

[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 cyclone 2 along the direction of slurry flow.

[0084] The homogenizer 1' comprises a homogenizing chamber 11', a collision ring 12' and a homogenizing collision valve 13'. The homogenizing chamber 11' and the homogenizing collision valve 13' are connected via the collision ring 12', and there is a gap between the homogenizing chamber 11' and the homogenizing collision valve 13' to provide a place for particle collision and a material transmission channel.

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

[0086] Application Example 1

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

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

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

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

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

[0092] Among them, the material ball ratio of the positive and negative electrode black powder slurry and the 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 a modified lithium iron phosphate particle product recovered by the above-mentioned recovery method with a lithium supplement agent and a reducing agent.

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

[0095] The modified lithium iron phosphate particle product, LiOH and PVP are mixed, the temperature is increased to 500° C. at a heating rate of 5° C. / min in a nitrogen atmosphere, and constant temperature solid phase sintering is performed for 2.5 hours to obtain the repaired lithium iron phosphate material.

[0096] Among them, the mass ratio of modified lithium iron phosphate particle product, LiOH and PVP is 1:0.2:0.05.

[0097] Figure 3 and Figure 4 The SEM images of the positive and negative electrode black powder and the modified lithium iron phosphate particle product in this embodiment are shown respectively. It can be seen from the figure that the positive and negative electrode black powder of the waste battery contains a large amount of graphite particles, and the lithium iron phosphate particles are agglomerated. In contrast, the surface of the modified lithium iron phosphate particle product is smooth, and the particle size is uniform and the morphology is uniform. In addition, no graphite is observed in the lithium iron phosphate material after homogenization, indicating that the graphite has been effectively separated.

[0098] Figure 5 and Figure 6 The low-magnification SEM image and high-magnification SEM image of graphite homogenized into graphene after separation of positive and negative electrode black powder in this embodiment are respectively shown. It can be seen from the figure that the homogenization process can effectively reduce the size and thickness of graphite to meet the standard of graphene. In particular, the cyclone can effectively separate the graphene product with lower density.

[0099] Figure 7 and Figure 8 The cycle performance comparison curve and capacity-voltage comparison curve 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 and discharge conditions, the initial capacity of the black powder is 108mAh / g; it quickly drops below 70mAh / g in the third cycle; after 50 charge and discharge cycles, only 37% is retained. In contrast, the initial test capacity of the repaired lithium iron phosphate material reaches 140mAh / g, reaching the commercial level; after the first 50 charge and discharge cycles, the capacity has almost no decay; after 100 cycles, it still has 91% capacity retention, showing good cycle stability. Figure 8 The difference in specific capacity between the two can be seen intuitively, and the repaired lithium iron phosphate material shows smaller 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 the above embodiment 2, and the specific steps include:

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

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

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

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

[0106] Among them, 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 a modified lithium iron phosphate particle product recovered by the above-mentioned recovery method with a lithium supplement agent and a reducing agent.

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

[0109] The modified lithium iron phosphate particle product, Li2CO3 and amino acid are mixed, heated to 700°C at a heating rate of 7°C / min in a nitrogen atmosphere, and subjected to constant temperature solid phase sintering for 3 hours to obtain the repaired lithium iron phosphate material.

[0110] Among them, the mass ratio of modified lithium iron phosphate particle product, Li2CO3 and amino acid 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 rest of the recycling methods and parameters remain the same as 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 rest of the recycling methods and parameters remain the same as those in Application Example 1.

[0117] Application Example 5

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

[0119] The rest of the recycling methods and parameters remain the same as those in Application Example 1.

[0120] Application Example 6

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

[0122] The rest of the recycling methods and parameters remain the same as 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 5 L / h.

[0125] The rest of the recycling methods and parameters remain the same as 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 rest of the recycling methods and parameters remain the same as those in Application Example 1.

[0129] Application Example 9

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

[0131] The rest of the recycling methods and parameters remain the same as those in Application Example 1.

[0132] Application Example 10

[0133] The difference between this application example and application example 1 is that the material-ball ratio of the positive and negative electrode black powder slurry and the sand milling medium in the sand mill is 1:50.

[0134] The rest of the recycling methods and parameters remain the same as 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 rest of the recycling methods and parameters remain the same as 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 rest of the recycling methods and parameters remain the same as those in Application Example 2.

[0141] Application Comparative Example 1

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

[0143] (1) The positive and negative black powders of used batteries are placed in a fixed bed reactor. The heat treatment atmosphere is argon gas. The heat treatment temperature is set to 600°C. The flow rate of water is 20 mL / h. The reaction time is 1.5 hours. The product gas and solid are obtained by gas-solid separation.

[0144] (2) The product gas is condensed, dried and dust-removed to achieve the collection and utilization of clean synthesis gas. 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 Application Comparative Example 1 of the present invention are respectively made into lithium ion batteries, and the specific steps include:

[0148] The repaired lithium iron phosphate material was mixed with conductive carbon black and binder in a mass ratio of 8:1:1, and a uniform slurry was obtained by a homogenizer; it was dripped on the carbon-coated aluminum foil and coated by a scraper; it was then dried in a forced air drying oven at 80°C for 6 hours; it was then cut into pieces to prepare a positive electrode sheet with a diameter of 13 mm; the positive electrode sheet was further dried in a vacuum oven at 120°C for 4 hours to obtain a prepared positive electrode sheet. Then, the positive electrode sheet was transferred to a glove box and the battery was assembled.

[0149] The assembly process includes selecting a lithium sheet as the counter electrode, combining it with a PP separator, and assembling it into a button-type half-cell in a layered manner. Among them, 100 μL of electrolyte is added dropwise, and 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 test conditions: charging and discharging test was performed at a rate of 1C.

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

[0152] Table 1

[0153]

[0154] analyze:

[0155] It can be seen from Application Example 1 and Application Examples 3-4 that 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 with each other unevenly, the homogenization effect is poor, 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 high, the separation effect is poor, and the final lithium iron phosphate product still contains a small amount of graphite, which affects the capacity.

[0156] It can be seen from Application Example 1 and Application Examples 5-6 that if the feed rate of the positive and negative electrode black powder slurry input into the sand mill in step (2) is low, precipitation is likely to occur in the cavity, resulting in poor homogenization effect, affecting the surface modification of the lithium iron phosphate material; if the feed rate of the positive and negative electrode black powder slurry input into the sand mill in step (2) is high, the grinding is insufficient, resulting in the inability of the cyclone to completely separate, and the bottom flow product still contains graphite, reducing the specific capacity.

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

[0158] It can be seen from Application Examples 1 and 9-10 that if the balls of the positive and negative electrode black powder slurry and the grinding medium in the sand mill are relatively small, the grinding is insufficient and the homogenization effect is poor, and the effect of modifying the lithium iron phosphate interface and exfoliating graphene by graphite cannot be achieved, which affects the capacity of the product after repair; if the balls of the positive and negative electrode black powder slurry and the grinding medium in the sand mill are relatively large, the fineness of the particles is affected, which affects the modification of the surface of the lithium iron phosphate particles, resulting in inconsistent structural repair in the subsequent lithium replenishment sintering, which in turn leads to a decrease in specific capacity.

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

[0160] It can be seen from Application Example 1 and Application Comparative Example 1 that, compared with the recovery method used in the prior art, the present application can better restore the structure and performance of lithium iron phosphate, mainly because the homogenization process modifies the surface of the failed lithium iron phosphate, which is conducive to the lithium replenishment process. At the same time, the graphite in the black powder is separated, and 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 illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by 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 positive and negative electrodes of waste batteries, characterized in that: The recovery method comprises the following steps: (1) Mixing the positive and negative electrode black powders of the waste battery with a solvent to obtain positive and negative electrode black powder slurry; Wherein, the positive and negative black powders of the waste battery include lithium iron phosphate black powder particles and graphite; (2) homogenizing the positive and negative electrode black powder slurries to obtain a homogenized material through material collision, and then separating to obtain a positive electrode product and a negative electrode product; Wherein, the homogenized material includes modified lithium iron phosphate particles and graphene.

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; and / or, the solvent comprises water; And / or, the solid content of the positive and negative electrode black powder slurry is 5-1000 mg / mL.

3. The recycling method according to claim 1, characterized in that: The homogenization process is a sand grinding process; And / or, the linear speed of the sanding is 1-12 m / s; And / or, during the sand milling process, the material-to-ball ratio of the positive and negative electrode black powder slurry and the sand milling medium is (1-50):(50-1); And / or, the sanding process time is 0.5-10h; 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 homogenization process is a self-generated collision homogenization process; And / or, during the self-generated collision homogenization process, the flow rate of the positive and negative electrode black powder slurry is 0.1-800L / h.

5. A slurry processing and separation device suitable for the recovery method according to any one of claims 1 to 4, characterized in that: The slurry processing and separation device includes a homogenizing device and a separation device along the direction of slurry flow; The homogenization device comprises a homogenization processing chamber, one end of which is provided with a feed port, and the other end of which is provided with a discharge port; the separation device comprises a separation chamber, the separation chamber is provided with a feed port, an underflow port and an overflow port, the feed port on the separation chamber is connected to the discharge port of the homogenization processing chamber, the underflow port and the overflow port are respectively located at the bottom and top of the separation chamber, and are respectively used to output positive electrode products and negative electrode products.

6. The slurry processing and separation device according to claim 5, characterized in that: The homogenizing device is a sand mill; And / or, the sand mill comprises a sand mill cavity, and a wall of the sand mill cavity is provided with an interlayer for circulating a cooling liquid; And / or, the sanding cavity is further provided with a coolant inlet and a coolant outlet, which are communicated with the interlayer; And / or, the discharge port of the same sand mill corresponds to the feed ports of multiple separation devices, or, the discharge ports of multiple sand mills correspond to the feed port of the same separation device.

7. The slurry processing and separation device according to claim 5, characterized in that: The homogenizing device is a homogenizer; And / or, the homogenizer comprises a homogenizing chamber, a collision ring and a homogenizing collision valve, the homogenizing chamber and the homogenizing collision valve are connected via the collision ring, and there is a gap between the homogenizing chamber and the homogenizing collision valve for providing a place for particle collision and a channel for material transmission; And / or, the discharge port of the same homogenizer corresponds to the feed ports of multiple separation devices, or, the discharge ports of multiple homogenizers correspond to the feed port of the same separation device.

8. The slurry processing and separation device according to claim 5, characterized in that: The separation device is a cyclone; And / or, the cyclone is a conical structure.

9. The slurry processing and separation device according to claim 5, characterized in that: The feed port in 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; And / or, the discharge port in the homogenization device is used to output the homogenized material, and the discharge flow rate of the homogenized material is 5-800 L / h.

10. A repaired lithium iron phosphate material, characterized in that: The repaired lithium iron phosphate material is obtained by solid-phase co-firing a positive electrode product recovered by the recovery method according to any one of claims 1 to 4 with a lithium supplement agent and a reducing agent.

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