A method for recycling and regenerating lithium iron phosphate waste

Abstract

The present invention relates to the technical field of lithium iron phosphate regeneration, and specifically relates to a method for recycling and regenerating lithium iron phosphate waste, comprising the following steps: disassembling, pulverizing, and sieving the lithium iron phosphate waste to obtain lithium iron phosphate powder; ingredient preparation: mixing lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate to obtain a mixed material, and then adding the lithium iron phosphate powder to the mixed material to obtain a blended material. The method for recycling and regenerating lithium iron phosphate waste in the present invention first disassembles, pulverizes, and sieves the lithium iron phosphate waste, and then cooperates with lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate to form a blended material, adding a filling balance agent, a modified synergistic agent, and a silane solution for ball milling treatment, and then roasting improvement. The product obtained by the waste recycling and regeneration treatment has excellent discharge specific capacity performance, and with the increase of charge and discharge rate, the rate discharge ratio performance stability is excellent. At the same time, the cycle capacity retention rate of the product is remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium iron phosphate regeneration, and specifically relates to a method for recycling and regenerating lithium iron phosphate waste materials. Background Art

[0002] With the rapid development of the new energy industry, the stock of waste power batteries has also experienced an explosive growth, and lithium iron phosphate batteries account for a large proportion. The existing lithium iron phosphate waste recycling and regeneration technology has a relatively simple process. After drying and crushing, the regenerated lithium iron phosphate cannot meet the normal battery performance requirements. The discharge specific capacity of the regenerated product is poor, and as the charge-discharge rate increases, the discharge rate performance deteriorates. At the same time, the cycle capacity retention rate of the product is low, which limits the use efficiency of the product. Summary of the Invention

[0003] Aiming at the defects of the existing technology, the purpose of the present invention is to provide a method for recycling and regenerating lithium iron phosphate waste materials to solve the problems raised in the above background art.

[0004] The present invention adopts the following technical solutions to solve the technical problems:

[0005] The present invention provides a method for recycling and regenerating lithium iron phosphate waste materials, including the following steps:

[0006] Step 1: Disassemble, crush and screen the lithium iron phosphate waste materials to obtain lithium iron phosphate powder.

[0007] Step 2: Prepare the ingredients: Mix lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate to obtain a mixed material, and then add lithium iron phosphate powder to the mixed material to obtain a blended material.

[0008] Step 3: Then add a filling agent accounting for 10-15% of the total weight of the blended material, a modified synergistic agent accounting for 5-8% of the total weight of the blended material, and a silane solution accounting for 20-25% of the total weight of the blended material to the blended material, and perform ball milling at a ball milling speed of 1500 r / min for 2 h. After the ball milling is completed, perform suction filtration and drying to obtain a precursor improved body.

[0009] Step 4: Roast the precursor improved body in a nitrogen atmosphere for 24 h at a roasting temperature of 750-800 °C. After the roasting is completed, perform crushing, screening and demagnetization.

[0010] Preferably, the lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate are mixed in a molar ratio of Li:Fe:P of 0.95:0.95:1; the addition amount of the lithium iron phosphate powder is 25-30% of the total amount of the mixed material.

[0011] Preferably, the preparation method of the filling agent is:

[0012] S1: immersing the carbon nanotubes in a cerium nitrate solution with a volume 3-5 times the total volume of the carbon nanotubes for ultrasonic treatment, with an ultrasonic power of 350-400W for 1 hour. After the ultrasonic treatment is completed, the carbon nanotubes are filtered and dried, and then heat-treated at a temperature of 270-280°C for 1 hour, and then returned to room temperature to obtain cerium-doped carbon nanotubes;

[0013] S2: 4-6 parts of zirconium nitrate solution, 0.25-0.35 parts of boron oxide, 2-3 parts of 5% by mass sodium alginate solution and 1-3 parts of gallium oxide are uniformly mixed to obtain a modified solution;

[0014] The zinc oxide whisker is stirred and modified in a modification liquid of 3-5 times the total amount of the zinc oxide whisker, the stirring temperature is 60-65° C., the stirring speed is 350-400 r / min, the stirring is continued for 2 hours, and the stirring is terminated to obtain a modified zinc oxide whisker body;

[0015] S3: The cerium-doped carbon nanotubes and the modified zinc oxide whiskers are mixed and ball-milled in a weight ratio of 5:3 at a ball-milling speed of 1000 r / min for 2 h. After the ball-milling is completed, the mixture is filtered and dried to obtain a filler.

[0016] Preferably, the mass concentration of the cerium nitrate solution is 0.5-0.8%; the mass concentration of the zirconium nitrate solution is 4-6%.

[0017] Preferably, the carbon nanotubes are multi-walled carbon nanotubes, and the multi-walled carbon nanotubes have a diameter of 50-55 nm and a length of 30-40 μm.

[0018] Preferably, the preparation method of the modified synergist is:

[0019] S11: Preparation of modifier based on titanium-lanthanum synergistic effect;

[0020] S12: stirring the graphene in a sufficient amount of 8% by mass sulfuric acid solution, then washing, filtering and drying;

[0021] 5-8 parts of dried graphene, 2-4 parts of aluminum nitride and 3-5 parts of sodium silicate solution are mixed and ball-milled at a ball-milling speed of 1000 r / min for 1 hour. After the ball-milling is completed, the mixture is filtered and dried to obtain a graphene synergist;

[0022] S13: The titanium-lanthanum synergist-based modifier and the graphene synergist are continuously blended and ball-milled in a weight ratio of 5:7 at a ball-milling speed of 1500 r / min for 2 h. After the ball-milling is completed, the modified synergist is filtered and dried to obtain the modified synergist.

[0023] Preferably, the mass fraction of the sodium silicate solution is 5-8%.

[0024] Preferably, the specific preparation method of the modifier based on titanium-lanthanum synergistic effect is:

[0025] Add 3 - 5 parts of strontium titanate and 2 - 3 parts of lanthanum oxide to 5 - 8 parts of sodium citrate solution, stir evenly to obtain a titanium - lanthanum solution;

[0026] Add 3 - 5 parts of tantalum pentoxide and 3 - 5 parts of polydopamine to 5 - 8 parts of sodium dodecylbenzenesulfonate solution and blend evenly to obtain a complexing agent;

[0027] Blend and stir - process the complexing agent and the strontium titanate solution according to a weight ratio of 5:(7 - 9). After the stirring ends, obtain a modifier based on the combined effect of titanium - lanthanum.

[0028] Preferably, the mass fraction of the sodium citrate solution is 4 - 7%; the mass fraction of the sodium dodecylbenzenesulfonate solution is 5 - 8%; the stirring speed of the blend - stirring process is 450 - 500 r / min, and stir for 1 h.

[0029] Preferably, the silane solution is prepared by mixing silane coupling agent KH550, ethanol solvent and water in a weight ratio of 2:7:4 and blending evenly.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. In the method for recycling and regenerating lithium iron phosphate waste of the present invention, first disassemble, crush and screen the lithium iron phosphate waste, then blend with lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate to form a blend, add a filling agent, a modified combined - effect agent and a silane solution for ball - milling treatment, and then improve by roasting. The product obtained by recycling and regenerating the waste has excellent discharge specific capacity performance, and with the increase of the charge - discharge rate, the rate discharge ratio performance is excellent in stability. At the same time, the cycle capacity retention rate of the product is remarkable;

[0032] 2. The filling agent is prepared by blending and ball - milling cerium - doped carbon nanotubes and modified zinc oxide whiskers. The cerium - doped carbon nanotubes are ultrasonically treated with cerium nitrate solution and then heat - treated at a temperature of 270 - 280 °C for 1 h. The carbon nanotubes have a high - specific - surface - area structure, and then combined with cerium elements, are filled into the system to enhance the interfacial property of the system and improve the performance stability of the product system. At the same time, the zinc oxide whiskers not only have the characteristics of zinc elements, but also have a whisker structure. After being stirred and improved by a modifying solution, the zirconium nitrate solution, boron oxide, 5% sodium alginate solution by mass fraction and gallium oxide in the modifying solution are blended and coordinated. The modifying solution is coordinated by raw materials such as zirconium nitrate solution, and is carried by the zinc oxide whiskers with a whisker structure, and then coordinated and improved with the cerium - doped carbon nanotubes. With the tubular structure of the carbon nanotubes and the whisker - like structure of the whiskers, through the hybridization and coordination between the structures, it is supplemented into the system to further enhance the performance stability of the system structure;

[0033] 3. The modified synergist is improved by co-milling a modifier based on titanium-lanthanum synergy and a graphene synergist. The modifier based on titanium-lanthanum synergy is prepared by blending and stirring a complexing agent and strontium titanate solution. The titanium-lanthanum solution is prepared by mixing strontium titanate, lanthanum oxide, and sodium citrate solution. At the same time, the sodium dodecylbenzenesulfonate solution in the complexing agent is coordinated with tantalum pentoxide and polydopamine. Raw materials such as tantalum, titanium, and lanthanum are incorporated into the system to enhance the performance effect of the system.

[0034] 4. At the same time, by combining the complexing agent with the titanium-lanthanum solution and using the mutual reinforcement and coordination between raw materials, the modifier based on titanium-lanthanum synergy can better improve and optimize the graphene synergist. The graphene synergist is prepared by treating graphene with sulfuric acid to optimize its activity efficiency, and then improved by co-milling with aluminum nitride and sodium silicate solution. The obtained graphene synergist is coordinated with the modifier based on titanium-lanthanum synergy. The prepared modified synergist further fills the system structure in the system, and the coordination effect between the modified synergist and the filler is further enhanced, thereby further improving the performance and performance stability of the product. Specific Embodiment

[0035] The following combines specific embodiments to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0036] A method for recycling and regenerating lithium iron phosphate waste in this embodiment includes the following steps:

[0037] Step 1: Disassemble, pulverize, and screen the lithium iron phosphate waste to obtain lithium iron phosphate powder.

[0038] Step 2: Prepare the ingredients: Mix lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate to obtain a mixed material, and then add the lithium iron phosphate powder to the mixed material to obtain a blended material.

[0039] Step 3: Subsequently, add a filler accounting for 10-15% of the total weight of the blended material, a modified synergist accounting for 5-8% of the total weight of the blended material, and a silane solution accounting for 20-25% of the total weight of the blended material to the blended material, and perform ball milling treatment at a ball milling speed of 1500 r / min for 2 h. After the ball milling is completed, perform suction filtration and drying to obtain a precursor-improved body.

[0040] Step 4: Roast the precursor-improved body in a nitrogen atmosphere for 24 h at a roasting temperature of 750-800 °C. After the roasting is completed, pulverize, screen, and demagnetize it.

[0041] In this embodiment, lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate are mixed in a ratio of 0.95:0.95:1 in terms of the molar ratio of Li:Fe:P; the addition amount of lithium iron phosphate powder is 25-30% of the total amount of the mixed material.

[0042] The preparation method of the filling balance agent in this embodiment is as follows:

[0043] S1: First, immerse the carbon nanotubes in a cerium nitrate solution that is 3-5 times the total amount of the carbon nanotubes and perform ultrasonic treatment. The ultrasonic power is 350-400 W, ultrasonic treatment is carried out for 1 h. After the ultrasonic treatment ends, perform suction filtration and drying, and then perform heat treatment at a temperature of 270-280 °C for 1 h, and restore to room temperature to obtain cerium-doped carbon nanotubes;

[0044] S2: Blend 4-6 parts of zirconium nitrate solution, 0.25-0.35 part of boron oxide, 2-3 parts of a 5% sodium alginate solution by mass, and 1-3 parts of gallium oxide uniformly to obtain a modified liquid;

[0045] Stir and modify zinc oxide whiskers in a modified liquid that is 3-5 times the total amount of the zinc oxide whiskers. The stirring temperature is 60-65 °C, the stirring speed is 350-400 r / min, stir for 2 h. After the stirring ends, obtain a modified zinc oxide whisker body;

[0046] S3: Blend the cerium-doped carbon nanotubes and the modified zinc oxide whisker body in a weight ratio of 5:3 and perform ball milling treatment. The ball milling speed is 1000 r / min, ball milling is carried out for 2 h. After the ball milling ends, perform suction filtration and drying to obtain the filling balance agent.

[0047] The mass concentration of the cerium nitrate solution in this embodiment is 0.5-0.8%; the mass concentration of the zirconium nitrate solution is 4-6%.

[0048] The carbon nanotubes in this embodiment are multi-walled carbon nanotubes. The diameter of the multi-walled carbon nanotubes is 50-55 nm, and the length is 30-40 μm.

[0049] The preparation method of the modified synergistic agent in this embodiment is as follows:

[0050] S11: Preparation of a modifier based on titanium-lanthanum synergy;

[0051] S12: First, stir graphene sufficiently in a sufficient amount of 8% sulfuric acid solution by mass, and then wash with water, perform suction filtration, and dry;

[0052] Blend 5-8 parts of dried graphene, 2-4 parts of aluminum nitride, and 3-5 parts of sodium silicate solution and perform ball milling treatment. The ball milling speed is 1000 r / min, ball milling is carried out for 1 h. After the ball milling ends, perform suction filtration and drying to obtain a graphene synergistic agent;

[0053] S13: Continue to blend and ball-mill the modifier based on the titanium-lanthanum synergy and the graphene synergy agent at a weight ratio of 5:7. The ball-milling speed is 1500 r / min, and the ball-milling time is 2 h. After the ball-milling is completed, perform suction filtration and drying to obtain the modified synergy agent.

[0054] In this embodiment, the mass fraction of the sodium silicate solution is 5-8%.

[0055] The specific preparation method of the modifier based on the titanium-lanthanum synergy in this embodiment is as follows:

[0056] Add 3-5 parts of strontium titanate and 2-3 parts of lanthanum oxide to 5-8 parts of sodium citrate solution, and stir evenly to obtain the titanium-lanthanum solution;

[0057] Add 3-5 parts of tantalum pentoxide and 3-5 parts of polydopamine to 5-8 parts of sodium dodecylbenzenesulfonate solution and blend evenly to obtain the complex modifier;

[0058] Blend and stir the complex modifier and the strontium titanate solution at a weight ratio of 5:(7-9). After the stirring is completed, obtain the modifier based on the titanium-lanthanum synergy.

[0059] In this embodiment, the mass fraction of the sodium citrate solution is 4-7%; the mass fraction of the sodium dodecylbenzenesulfonate solution is 5-8%; the stirring speed for the blending and stirring treatment is 450-500 r / min, and the stirring time is 1 h.

[0060] In this embodiment, the silane solution is prepared by uniformly mixing silane coupling agent KH550, ethanol solvent, and water at a weight ratio of 2:7:4.

[0061] Example 1.

[0062] A method for recycling and regenerating lithium iron phosphate waste in this embodiment includes the following steps:

[0063] Step 1: Disassemble, crush, and screen the lithium iron phosphate waste to obtain lithium iron phosphate powder;

[0064] Step 2: Prepare the ingredients: Mix lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate to obtain a mixed material body, and then add the lithium iron phosphate powder to the mixed material body to obtain a blended body;

[0065] Step 3: Subsequently, add a filling agent accounting for 10% of the total weight of the blended body, a modified synergy agent accounting for 5% of the total weight of the blended body, and a silane solution accounting for 20% of the total weight of the blended body to the blended body, and perform ball-milling. The ball-milling speed is 1500 r / min, and the ball-milling time is 2 h. After the ball-milling is completed, perform suction filtration and drying to obtain a precursor improved body;

[0066] Step 4: Calcinate the precursor improved body in a nitrogen atmosphere for 24 h at a calcination temperature of 750 °C. After the calcination is completed, perform crushing, screening, and demagnetization.

[0067] In this embodiment, lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate are mixed in a molar ratio of Li:Fe:P of 0.95:0.95:1; the amount of lithium iron phosphate powder added is 25% of the total amount of the mixture.

[0068] The preparation method of the filler in this embodiment is:

[0069] S1: immersing the carbon nanotubes in a cerium nitrate solution with a volume of 3-5 times the total volume of the carbon nanotubes for ultrasonic treatment, with an ultrasonic power of 350 W for 1 hour. After the ultrasonic treatment is completed, the carbon nanotubes are filtered and dried, and then heat-treated at 270° C. for 1 hour, and then returned to room temperature to obtain cerium-doped carbon nanotubes;

[0070] S2: 4 parts of zirconium nitrate solution, 0.25 parts of boron oxide, 2 parts of 5% by mass sodium alginate solution and 1 part of gallium oxide are uniformly mixed to obtain a modified solution;

[0071] The zinc oxide whisker was stirred and modified in a modification liquid of 3 times the total amount of the zinc oxide whisker, the stirring temperature was 60°C, the stirring speed was 350r / min, the stirring was continued for 2h, and the modified zinc oxide whisker body was obtained after the stirring was completed;

[0072] S3: The cerium-doped carbon nanotubes and the modified zinc oxide whiskers are mixed and ball-milled in a weight ratio of 5:3 at a ball-milling speed of 1000 r / min for 2 h. After the ball-milling is completed, the mixture is filtered and dried to obtain a filler.

[0073] The mass concentration of the cerium nitrate solution in this embodiment is 0.5%; the mass concentration of the zirconium nitrate solution is 4%.

[0074] The carbon nanotubes in this embodiment are multi-walled carbon nanotubes, and the multi-walled carbon nanotubes have a diameter of 50 nm and a length of 30 μm.

[0075] The preparation method of the modified synergist of this embodiment is:

[0076] S11: Preparation of modifier based on titanium-lanthanum synergistic effect;

[0077] S12: stirring the graphene in a sufficient amount of 8% by mass sulfuric acid solution, then washing, filtering and drying;

[0078] 5 parts of dried graphene, 2 parts of aluminum nitride and 3 parts of sodium silicate solution were mixed and ball-milled at a ball-milling speed of 1000 r / min for 1 hour. After the ball-milling was completed, the mixture was filtered and dried to obtain a graphene synergist.

[0079] S13: The titanium-lanthanum synergist-based modifier and the graphene synergist are continuously blended and ball-milled in a weight ratio of 5:7 at a ball-milling speed of 1500 r / min for 2 h. After the ball-milling is completed, the modified synergist is filtered and dried to obtain the modified synergist.

[0080] The mass fraction of the sodium silicate solution in this embodiment is 5%.

[0081] The specific preparation method of the modifier based on the titanium-lanthanum synergy in this embodiment is as follows:

[0082] Add 3 parts of strontium titanate and 2 parts of lanthanum oxide to 5 parts of sodium citrate solution, stir evenly to obtain the titanium-lanthanum solution;

[0083] Add 3 parts of tantalum pentoxide and 3 parts of polydopamine to 5 parts of sodium dodecylbenzenesulfonate solution and blend evenly to obtain the complex modifier;

[0084] Blend and stir the complex modifier and the strontium titanate solution according to a weight ratio of 5:7. After stirring ends, obtain the modifier based on the titanium-lanthanum synergy.

[0085] The mass fraction of the sodium citrate solution in this embodiment is 4%; the mass fraction of the sodium dodecylbenzenesulfonate solution is 5%; the stirring speed for the blend and stir treatment is 450 r / min, and stir for 1 h.

[0086] The silane solution in this embodiment is prepared by uniformly blending silane coupling agent KH550, ethanol solvent and water according to a weight ratio of 2:7:4.

[0087] Example 2.

[0088] A method for recycling and regenerating lithium iron phosphate waste in this embodiment includes the following steps:

[0089] Step 1: Disassemble, crush and screen the lithium iron phosphate waste to obtain lithium iron phosphate powder;

[0090] Step 2: Ingredient preparation: Mix lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate to obtain a mixed material body, and then add lithium iron phosphate powder to the mixed material body to obtain a blended body;

[0091] Step 3: Then add a filling balance agent accounting for 15% of the total weight of the blended body, a modified synergy agent accounting for 8% of the total weight of the blended body and a silane solution accounting for 25% of the total weight of the blended body to the blended body, perform ball milling treatment, with a ball milling speed of 1500 r / min and ball milling for 2 h. After ball milling ends, carry out suction filtration and drying to obtain a precursor improved body;

[0092] Step 4: Roast the precursor improved body in a nitrogen atmosphere for 24 h, with a roasting temperature of 800 °C. After roasting ends, crush, screen and demagnetize it.

[0093] In this embodiment, lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate are mixed in a molar ratio of Li:Fe:P of 0.95:0.95:1; the addition amount of the lithium iron phosphate powder is 30% of the total amount of the mixed material body.

[0094] The preparation method of the filler in this embodiment is:

[0095] S1: first immerse the carbon nanotubes in a cerium nitrate solution with a volume of 3-5 times the total volume of the carbon nanotubes for ultrasonic treatment, with an ultrasonic power of 400 W for 1 hour, and then filter and dry, and then heat treat at 280° C. for 1 hour, and then return to room temperature to obtain cerium-doped carbon nanotubes;

[0096] S2: 6 parts of zirconium nitrate solution, 0.35 parts of boron oxide, 3 parts of 5% by mass sodium alginate solution and 3 parts of gallium oxide are uniformly mixed to obtain a modified solution;

[0097] The zinc oxide whiskers were stirred and modified in a modification liquid of 5 times the total amount of the zinc oxide whiskers, the stirring temperature was 65°C, the stirring speed was 400r / min, the stirring was continued for 2h, and the modified zinc oxide whiskers were obtained after the stirring was completed;

[0098] S3: The cerium-doped carbon nanotubes and the modified zinc oxide whiskers are mixed and ball-milled in a weight ratio of 5:3 at a ball-milling speed of 1000 r / min for 2 h. After the ball-milling is completed, the mixture is filtered and dried to obtain a filler.

[0099] The mass concentration of the cerium nitrate solution in this embodiment is 0.8%; the mass concentration of the zirconium nitrate solution is 6%.

[0100] The carbon nanotubes in this embodiment are multi-walled carbon nanotubes, and the multi-walled carbon nanotubes have a diameter of 55 nm and a length of 40 μm.

[0101] The preparation method of the modified synergist of this embodiment is:

[0102] S11: Preparation of modifier based on titanium-lanthanum synergistic effect;

[0103] S12: stirring the graphene in a sufficient amount of 8% by mass sulfuric acid solution, then washing, filtering and drying;

[0104] 8 parts of dried graphene, 4 parts of aluminum nitride and 5 parts of sodium silicate solution were mixed and ball-milled at a ball-milling speed of 1000 r / min for 1 hour. After the ball-milling was completed, the mixture was filtered and dried to obtain a graphene synergist.

[0105] S13: The titanium-lanthanum synergist-based modifier and the graphene synergist are continuously blended and ball-milled in a weight ratio of 5:7 at a ball-milling speed of 1500 r / min for 2 h. After the ball-milling is completed, the modified synergist is filtered and dried to obtain the modified synergist.

[0106] The mass fraction of the sodium silicate solution in this embodiment is 8%.

[0107] The specific preparation method of the modifier based on titanium-lanthanum synergistic effect of this embodiment is:

[0108] Add 5 parts of strontium titanate and 3 parts of lanthanum oxide to 8 parts of sodium citrate solution, stir evenly to obtain a titanium-lanthanum solution;

[0109] Add 5 parts of tantalum pentoxide and 5 parts of polydopamine to 8 parts of sodium dodecylbenzenesulfonate solution, blend evenly to obtain a complexing agent;

[0110] Blend and stir the complexing agent and the strontium titanate solution according to a weight ratio of 5:9, and after stirring ends, obtain a modifier based on the combined effect of titanium and lanthanum.

[0111] In this example, the mass fraction of the sodium citrate solution is 7%; the mass fraction of the sodium dodecylbenzenesulfonate solution is 8%; the stirring speed for the blend and stir treatment is 500 r / min, and stir for 1 h.

[0112] The silane solution in this example is prepared by uniformly blending silane coupling agent KH550, ethanol solvent and water according to a weight ratio of 2:7:4.

[0113] Example 3.

[0114] A method for recycling and regenerating lithium iron phosphate waste in this example includes the following steps:

[0115] Step 1: Disassemble, crush and screen the lithium iron phosphate waste to obtain lithium iron phosphate powder;

[0116] Step 2: Ingredient preparation: Mix lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate to obtain a mixed material body, and then add lithium iron phosphate powder to the mixed material body to obtain a blended body;

[0117] Step 3: Subsequently, add a filling balance agent accounting for 12.5% of the total weight of the blended body, a modified combined effect agent accounting for 6.5% of the total weight of the blended body and a silane solution accounting for 22.5% of the total weight of the blended body to the blended body, perform ball milling treatment, with a ball milling speed of 1500 r / min and ball milling for 2 h. After ball milling ends, perform suction filtration and drying to obtain a precursor improved body;

[0118] Step 4: Roast the precursor improved body in a nitrogen atmosphere for 24 h, with a roasting temperature of 775 °C. After roasting ends, perform crushing, screening and demagnetization.

[0119] In this example, lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate are mixed according to a molar ratio of Li:Fe:P of 0.95:0.95:1; the addition amount of the lithium iron phosphate powder is 27.5% of the total amount of the mixed material body.

[0120] The preparation method of the filling balance agent in this example is:

[0121] S1: The carbon nanotubes were first immersed in a cerium nitrate solution with a volume 4 times the total volume of the carbon nanotubes for ultrasonic treatment at an ultrasonic power of 375 W for 1 h. After the ultrasonic treatment was completed, the carbon nanotubes were filtered and dried, and then heat treated at 275°C for 1 h, and then returned to room temperature to obtain cerium-doped carbon nanotubes;

[0122] S2: 5 parts of zirconium nitrate solution, 0.30 parts of boron oxide, 2.5 parts of 5% by mass sodium alginate solution and 2 parts of gallium oxide are uniformly mixed to obtain a modified solution;

[0123] The zinc oxide whiskers were stirred and modified in a modification liquid of 4 times the total amount of the zinc oxide whiskers, the stirring temperature was 62.5°C, the stirring speed was 375r / min, the stirring was continued for 2h, and the modified zinc oxide whiskers were obtained after the stirring was completed;

[0124] S3: The cerium-doped carbon nanotubes and the modified zinc oxide whiskers are mixed and ball-milled in a weight ratio of 5:3 at a ball-milling speed of 1000 r / min for 2 h. After the ball-milling is completed, the mixture is filtered and dried to obtain a filler.

[0125] The mass concentration of the cerium nitrate solution in this embodiment is 0.65%; the mass concentration of the zirconium nitrate solution is 5%.

[0126] The carbon nanotubes in this embodiment are multi-walled carbon nanotubes, and the multi-walled carbon nanotubes have a diameter of 52.5 nm and a length of 35 μm.

[0127] The preparation method of the modified synergist of this embodiment is:

[0128] S11: Preparation of modifier based on titanium-lanthanum synergistic effect;

[0129] S12: stirring the graphene in a sufficient amount of 8% by mass sulfuric acid solution, then washing, filtering and drying;

[0130] 6.5 parts of dried graphene, 3 parts of aluminum nitride and 4 parts of sodium silicate solution were mixed and ball-milled at a ball-milling speed of 1000 r / min for 1 hour. After the ball-milling was completed, the mixture was filtered and dried to obtain a graphene synergist.

[0131] S13: The titanium-lanthanum synergist-based modifier and the graphene synergist are continuously blended and ball-milled in a weight ratio of 5:7 at a ball-milling speed of 1500 r / min for 2 h. After the ball-milling is completed, the modified synergist is filtered and dried to obtain the modified synergist.

[0132] The mass fraction of the sodium silicate solution in this embodiment is 6.5%.

[0133] The specific preparation method of the modifier based on titanium-lanthanum synergistic effect of this embodiment is:

[0134] Add 4 parts of strontium titanate and 2.5 parts of lanthanum oxide to 6.5 parts of sodium citrate solution, stir evenly to obtain a titanium-lanthanum solution;

[0135] Add 4 parts of tantalum pentoxide and 4 parts of polydopamine to 6.5 parts of sodium dodecylbenzenesulfonate solution, blend evenly to obtain a modifier;

[0136] Blend and stir the modifier and the strontium titanate solution according to a weight ratio of 5:8. After stirring, obtain a modifier based on the combined effect of titanium and lanthanum.

[0137] In this example, the mass fraction of the sodium citrate solution is 5.5%; the mass fraction of the sodium dodecylbenzenesulfonate solution is 6.5%; the stirring speed for the blending and stirring treatment is 475 r / min, and stir for 1 h.

[0138] The silane solution in this example is prepared by uniformly mixing silane coupling agent KH550, ethanol solvent and water according to a weight ratio of 2:7:4.

[0139] Comparative Example 1.

[0140] The difference from Example 3 is that the filler is not added.

[0141] Comparative Example 2.

[0142] The difference from Example 3 is that cerium-doped carbon nanotubes are not added in the preparation of the filler.

[0143] Comparative Example 3.

[0144] The difference from Example 3 is that modified zinc oxide whiskers are not added in the preparation of the filler.

[0145] Comparative Example 4.

[0146] The difference from Example 3 is that the modification liquid is not added in the preparation of the modified zinc oxide whiskers.

[0147] Comparative Example 5.

[0148] The difference from Example 3 is that gallium oxide and boron oxide are not added to the modification liquid.

[0149] Comparative Example 6.

[0150] The difference from Example 3 is that the zirconium nitrate solution is not added to the modification liquid and the sodium alginate solution is replaced with water.

[0151] Comparative Example 7.

[0152] The difference from Example 3 is that the modified combined effect agent is not added.

[0153] Comparative Example 8.

[0154] The difference from Example 3 is that the graphene combined effect agent is not added in the preparation of the modified combined effect agent.

[0155] Comparative Example 9

[0156] The difference from Example 3 is that aluminum nitride and sodium silicate solution were not added during the preparation of the graphene synergist.

[0157] Comparative Example 10

[0158] The difference from Example 3 is that the modifier based on titanium-lanthanum synergism was not added during the preparation of the modified synergist.

[0159] Comparative Example 11

[0160] The difference from Example 3 is that silane solution was not added.

[0161] The products of Examples 1-3 and Comparative Examples 1-11 were made into button batteries by the prior art and their electrical properties were tested at a voltage of 2.0 - 3.8V. The performance tests are as follows;

[0162]

[0163] It can be seen from Comparative Examples 1-11 and Example 3 that the products of Example 3 are excellent in both 0.1C discharge specific capacity and 5C discharge specific capacity. At the same time, the 5C / 0.1C discharge ratio performance stability is remarkable. And after 200 times and 500 times of cycling under 5C conditions, the cycle capacity retention performance of the products remains stable;

[0164] If one of the filler and the modified synergist is not added to the product, the performance of the product deteriorates significantly. When the two are blended and coordinated together, the performance effect of the product is the most remarkable;

[0165] If cerium-doped carbon nanotubes were not added during the preparation of the filler, if modified zinc oxide whiskers were not added during the preparation of the filler, if the modified liquid was not added during the preparation of the modified zinc oxide whiskers, if gallium oxide and boron oxide were not added to the modified liquid, if zirconium nitrate solution was not added to the modified liquid, and if water was used instead of sodium alginate solution, the performance of the products all showed a trend of deterioration to varying degrees; The preparation of the modified liquid of the present invention is specific, and the method of the present invention has the best effect;

[0166] And the product with the best performance effect is the filler made of modified zinc oxide whiskers improved by the modified liquid obtained by the specific method of the present invention and cerium-doped carbon nanotubes. Replacing it with other methods is not as effective as the present invention;

[0167] When graphene synergist is not added during the preparation of the modified synergist, aluminum nitride and sodium silicate solution are not added during the preparation of the graphene synergist, the modifier based on titanium-lanthanum synergism and silane solution are not added during the preparation of the modified synergist, the performance of the product shows a deteriorating trend. The performance effect of the modified synergist obtained by the specific method of the present invention is the most significant. When the modifier based on titanium-lanthanum synergism is not added during the preparation of the modified synergist, the performance of the product deteriorates significantly. At the same time, with the cooperation of the silane solution of the present invention, the performance of the product can also be improved to a certain extent.

[0168] In addition, the inventors of the present invention found that when the product is not treated with the modifier based on titanium-lanthanum synergism, the performance of the product shows an obvious deteriorating trend. In this regard, the present invention further explores and processes it.

[0169] Experimental Example 1.

[0170] Same as Example 3, except that the compounding agent is not added to the modifier based on titanium-lanthanum synergism.

[0171] Experimental Example 2.

[0172] Same as Example 3, except that tantalum pentoxide is not added to the compounding agent.

[0173] Experimental Example 3.

[0174] Same as Example 3, except that strontium titanate solution is not added to the modifier based on titanium-lanthanum synergism.

[0175] Experimental Example 4.

[0176] Same as Example 3, except that strontium titanate is not added to the strontium titanate solution.

[0177] Experimental Example 5.

[0178] Same as Example 3, except that lanthanum oxide is not added to the strontium titanate solution.

[0179] Regarding the influence of the preparation method of the modifier based on titanium-lanthanum synergism on the product performance, the performance tests of the products in Experimental Examples 1-5 are as follows:

[0180]

[0181] It can be seen from Experimental Examples 1-5 that without adding strontium titanate solution and compounding agent to the modifier based on the titanium-lanthanum synergy effect, the performance of the product deteriorates significantly. At the same time, without adding tantalum pentoxide to the compounding agent, without adding strontium titanate to the strontium titanate solution, and without adding lanthanum oxide to the strontium titanate solution, the performance of the product shows a deteriorating trend to varying degrees. The selection of the strontium titanate solution is proprietary. The modifier based on the titanium-lanthanum synergy effect prepared by combining the strontium titanate solution obtained by the specific method of the present invention with the compounding agent has the most significant performance effect. Replacing it with other methods is not as obvious as the effect of the present invention.

[0182] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed by the present invention.

[0183] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for recycling and regenerating lithium iron phosphate waste, characterized in that, It includes the following steps: Step 1: Disassemble, crush, and screen the lithium iron phosphate waste to obtain lithium iron phosphate powder; Step 2: Mix lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate to obtain a mixed material body, and then add lithium iron phosphate powder to the mixed material body to obtain a blended body; Step 3: Subsequently, add a filling balance agent accounting for 10 - 15% of the total weight of the blended body, a modified synergistic agent accounting for 5 - 8% of the total weight of the blended body, and a silane solution accounting for 20 - 25% of the total weight of the blended body to the blended body, perform ball milling treatment, with a ball milling speed of 1500 r / min and ball milling for 2 h. After the ball milling is completed, perform suction filtration and drying to obtain a precursor improved body; Step 4: Calcinate the precursor improved body in a nitrogen atmosphere for 24 h, with a calcination temperature of 750 - 800 °C. After the calcination is completed, perform pulverization, screening, and demagnetization; The preparation method of the filling balance agent is as follows: S1: Immerse carbon nanotubes into a cerium nitrate solution 3 - 5 times the total amount of carbon nanotubes and perform ultrasonic treatment. The ultrasonic power is 350 - 400 W, and ultrasonic treatment is performed for 1 h. After the ultrasonic treatment is completed, perform suction filtration and drying, and then perform heat treatment at a temperature of 270 - 280 °C for 1 h and return to room temperature to obtain cerium-doped carbon nanotubes; S2: Blend 4 - 6 parts of zirconium nitrate solution, 0.25 - 0.35 parts of boron oxide, 2 - 3 parts of a 5% sodium alginate solution by mass, and 1 - 3 parts of gallium oxide evenly to obtain a modified liquid; Stir and modify zinc oxide whiskers in a modified liquid 3 - 5 times the total amount of zinc oxide whiskers. The stirring temperature is 60 - 65 °C, the stirring speed is 350 - 400 r / min, and stirring is performed for 2 h. After the stirring is completed, obtain a modified zinc oxide whisker body; S3: Blend the cerium-doped carbon nanotubes and the modified zinc oxide whisker body in a weight ratio of 5:3 and perform ball milling treatment. The ball milling speed is 1000 r / min, and ball milling is performed for 2 h. After the ball milling is completed, perform suction filtration and drying to obtain the filling balance agent.

2. The recycling and regeneration treatment method of lithium iron phosphate waste according to claim 1, characterized in that, The lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate are mixed in a molar ratio of Li:Fe:P of 0.95:0.95:1; the addition amount of the lithium iron phosphate powder is 25 - 30% of the total amount of the mixed material body.

3. A method for recycling and regenerating lithium iron phosphate waste according to claim 1, characterized in that, The mass concentration of the cerium nitrate solution is 0.5 - 0.8%; the mass concentration of the zirconium nitrate solution is 4 - 6%.

4. A method for recycling and regenerating lithium iron phosphate waste according to claim 1, characterized in that, The carbon nanotubes are multi-walled carbon nanotubes, with a diameter of 50 - 55 nm and a length of 30 - 40 μm.

5. A method for recycling and regenerating lithium iron phosphate waste according to claim 1, characterized in that, The preparation method of the modified synergistic agent is as follows: S11: Preparation of a modifier based on titanium-lanthanum synergy; S12: First, stir graphene sufficiently in a sufficient amount of 8% sulfuric acid solution by mass, and then perform water washing, suction filtration, and drying; Blend 5 - 8 parts of dried graphene, 2 - 4 parts of aluminum nitride, and 3 - 5 parts of a sodium silicate solution by mass and perform ball milling treatment. The ball milling speed is 1000 r / min, and ball milling is performed for 1 h. After the ball milling is completed, perform suction filtration and drying to obtain a graphene synergistic agent; S13: Blend the modifier based on titanium-lanthanum synergy and the graphene synergistic agent in a weight ratio of 5:7 and continue to perform ball milling treatment. The ball milling speed is 1500 r / min, and ball milling is performed for 2 h. After the ball milling is completed, perform suction filtration and drying to obtain the modified synergistic agent.

6. The recycling and regeneration treatment method of lithium iron phosphate waste according to claim 5, characterized in that, The mass fraction of the sodium silicate solution is 5 - 8%.

7. A method for recycling and regenerating lithium iron phosphate waste according to claim 5, characterized in that, The specific preparation method of the modifier based on titanium-lanthanum synergy is: Add 3-5 parts of strontium titanate and 2-3 parts of lanthanum oxide to 5-8 parts of sodium citrate solution, and stir evenly to obtain a titanium-lanthanum solution; Add 3-5 parts of tantalum pentoxide and 3-5 parts of polydopamine to 5-8 parts of sodium dodecylbenzenesulfonate solution and blend evenly to obtain a complex modifier; Blend and stir the complex modifier and the strontium titanate solution according to a weight ratio of 5:(7-9), and after the stirring ends, obtain a modifier based on the synergistic effect of titanium and lanthanum.

8. A recycling and regeneration treatment method for lithium iron phosphate waste according to claim 7, characterized in that, The mass fraction of the sodium citrate solution is 4-7%; the mass fraction of the sodium dodecylbenzenesulfonate solution is 5-8%; the stirring speed for the blending and stirring treatment is 450-500 r / min, and stir for 1 h.

9. A recycling and regeneration treatment method for lithium iron phosphate waste according to claim 1, characterized in that The silane solution is prepared by uniformly blending silane coupling agent KH550, ethanol solvent and water according to a weight ratio of 2:7:4.

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