CN112658000B - Method for recycling leftover materials of positive plate of lithium iron phosphate battery - Google Patents
Method for recycling leftover materials of positive plate of lithium iron phosphate battery Download PDFInfo
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 130
- 239000000463 material Substances 0.000 title claims abstract description 86
- 238000000034 method Methods 0.000 title claims abstract description 78
- 238000004064 recycling Methods 0.000 title claims abstract description 22
- 239000000843 powder Substances 0.000 claims abstract description 66
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 54
- 238000001354 calcination Methods 0.000 claims abstract description 45
- 229910052742 iron Inorganic materials 0.000 claims abstract description 27
- 238000012216 screening Methods 0.000 claims abstract description 26
- 239000012535 impurity Substances 0.000 claims abstract description 25
- 239000012298 atmosphere Substances 0.000 claims abstract description 17
- 239000002699 waste material Substances 0.000 claims abstract description 17
- 239000011362 coarse particle Substances 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000010902 jet-milling Methods 0.000 claims abstract description 5
- 239000010406 cathode material Substances 0.000 claims description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 238000004321 preservation Methods 0.000 claims description 11
- 238000005245 sintering Methods 0.000 claims description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 230000006698 induction Effects 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 239000001307 helium Substances 0.000 claims description 4
- 229910052734 helium Inorganic materials 0.000 claims description 4
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 238000005265 energy consumption Methods 0.000 abstract description 11
- 239000010405 anode material Substances 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 230000002195 synergetic effect Effects 0.000 abstract description 3
- 239000007774 positive electrode material Substances 0.000 description 23
- 230000000052 comparative effect Effects 0.000 description 14
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 6
- 238000002485 combustion reaction Methods 0.000 description 6
- 239000002245 particle Substances 0.000 description 5
- 230000001172 regenerating effect Effects 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000007873 sieving Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
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- 238000004146 energy storage Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/20—Waste processing or separation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/84—Recycling of batteries or fuel cells
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Abstract
The invention provides a method for recycling leftover materials of a positive plate of a lithium iron phosphate battery. The method comprises the following steps: firstly, crushing leftover materials into coarse particles, then calcining the coarse particles in an inert atmosphere, crushing the materials into fine materials after the materials are cooled, and removing impurities through air flow classification and dry powder iron removal processes to obtain waste lithium iron phosphate powder; and calcining the waste lithium iron phosphate powder in an inert atmosphere, cooling the material, performing jet milling to obtain fine lithium iron phosphate powder, and performing secondary impurity removal and screening to remove iron to obtain the lithium iron phosphate anode material. Through the mode, the method can reduce the temperature and time required by the calcining process by utilizing the synergistic effect among the steps, and effectively remove impurities in the lithium iron phosphate, so that the leftover materials of the positive plate of the lithium iron phosphate battery can be recycled by the simplest step, the lowest energy consumption and a safe and environment-friendly production mode, and the lithium iron phosphate positive material with excellent performance is obtained, so that the requirement of practical application is met.
Description
Technical Field
The invention relates to the technical field of lithium ion battery waste recovery, in particular to a method for recovering and regenerating leftover materials of a positive plate of a lithium iron phosphate battery.
Background
The lithium iron phosphate is of an olivine structure, the theoretical specific capacity of the lithium iron phosphate is 170mAh/g, the cycle number can reach more than 2000 times, and the lithium iron phosphate is stable in performance, safe, environment-friendly and low in price, so that the lithium iron phosphate is widely applied to the fields of new energy automobiles, energy storage batteries and the like. In recent years, the wide application of lithium iron phosphate has greatly increased the output, but waste scraps are generated in the production process of lithium iron phosphate batteries, both in the coating process and the pole piece punching process. If the leftover materials cannot be effectively recycled, the resource is seriously wasted.
At present, the leftover materials are generally recovered and treated by an acid-soluble, alkali-soluble or NMP-soaked mode, and the products are usually Li 2 CO 3 And FePO 4 And the like, and further producing the lithium iron phosphate cathode material by using the lithium iron phosphate cathode material as a raw material. The whole process flow is complex, the working procedures are multiple, the labor energy consumption is high, the overall production cost is high, the processes can involve acid, alkali or NMP, and the process has great safety and environmental protection risks.
For example, patent publication No. CN105895854A provides a method for recovering leftover bits and pieces of positive electrodes of lithium ion batteries, which comprises sufficiently pulverizing the leftover bits and pieces, calcining at 450-650 ℃, sieving to remove aluminum after calcining, washing with alkaline solution, filtering, washing, and drying to obtain the positive electrode material. In the process, although the alkaline solution can be repeatedly used, the bottom slurry obtained after alkaline washing still generates a large amount of alkaline waste liquid in the washing process, and the environmental hazard is large. Therefore, how to realize the recycling of the leftover materials safely and environmentally without using acid, alkali or NMP is the focus of current research.
The patent with publication number CN110752415A provides a process for sorting and utilizing an anode material of a retired lithium iron phosphate battery, and the process comprises the steps of shearing the anode material, calcining, screening to remove aluminum, oxidizing and roasting, sequentially batching, ball milling, drying, reducing and regenerating, airflow crushing and screening to remove iron, and finally obtaining a lithium iron phosphate product. In the process, acid-base solution is not used, but the process is too complex, three times of calcination are carried out, the sintering temperature in the oxidizing roasting and reducing regeneration processes is high, the time is long, the overall energy consumption is very high, and the requirements of practical application are difficult to meet.
In view of the above, there is a need to design a method for recycling leftover materials of positive electrode plates of lithium iron phosphate batteries under the conditions of low energy consumption and no pollution, so as to solve the above problems.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a method for recycling leftover materials of positive plates of lithium iron phosphate batteries. Through the reasonable design of multistage crushing, calcining and impurity removal processes, under the condition of not using acid, alkali and toxic solvents, the leftover materials of the positive plate of the lithium iron phosphate battery are directly recycled and regenerated into the lithium iron phosphate positive material with lower energy consumption, so as to meet the requirements of practical application.
In order to achieve the purpose, the invention provides a method for recycling leftover materials of positive plates of lithium iron phosphate batteries, which comprises the following steps:
s1, coarse crushing: crushing leftover materials to be recovered into coarse particles of 1-10 mm;
s2, first burning: calcining the coarse particles for the first time in an inert atmosphere, and cooling to a preset temperature to obtain a primary calcined material;
s3, fine crushing: crushing the primary burned material into D 50 Is powder of 2-150 mu m to obtain fine crushed material;
s4, primary impurity removal: carrying out airflow classification on the fine crushed material, and screening out aluminum in the fine crushed material; then screening and dry powder deironing are sequentially carried out to obtain waste lithium iron phosphate powder;
s5, secondary sintering: calcining the waste lithium iron phosphate powder for the second time in an inert atmosphere, and cooling to a preset temperature to obtain a secondary calcined material;
s6, airflow crushing: performing jet milling on the secondary sintering material to obtain lithium iron phosphate fine powder;
s7, secondary impurity removal: sequentially carrying out dry powder iron removal and air flow grading carbon removal on the lithium iron phosphate fine powder to obtain lithium iron phosphate powder;
s8, screening and deironing: and after carrying out vibration screening on the lithium iron phosphate powder, removing iron by using dry powder to obtain the lithium iron phosphate anode material.
As a further improvement of the invention, in step S2, the calcination temperature of the first calcination is 320-500 ℃, and the heat preservation time is 1-2 h.
As a further improvement of the invention, in step S5, the calcination temperature of the second calcination is 450-600 ℃, and the holding time is 1-4 h.
As a further improvement of the invention, in the steps S2 and S5, the inert atmosphere is one or more of nitrogen, argon and helium, and the oxygen content in the inert atmosphere is less than or equal to 1ppm.
As a further development of the invention, in steps S2 and S5, the predetermined temperature is below 100 ℃.
As a further improvement of the invention, in step S4, the vibrating screen used in the screening process is 20-40 meshes.
As a further improvement of the present invention, in step S6, D of the lithium iron phosphate fine powder 50 0.6 to 2.0 μm.
As a further improvement of the present invention, in step S7, the carbon content of the lithium iron phosphate powder is 1% to 3%.
As a further improvement of the present invention, in step S8, the vibrating screen used in the vibrating screening process is 40 to 100 mesh.
As a further improvement of the invention, in the steps S4, S7 and S8, the dry powder iron removal process is carried out in a dry powder iron remover with the magnetic induction intensity of more than or equal to 12000 Gs.
The beneficial effects of the invention are:
(1) The method for recycling the leftover materials of the positive plate of the lithium iron phosphate battery sequentially comprises the steps of coarse crushing, primary burning, fine crushing, primary impurity removal, secondary burning, airflow crushing, secondary impurity removal, screening and iron removal and the like of the leftover materials. According to the arrangement mode, the particle size of the leftover materials is reduced in the coarse crushing process, so that the binder mixed in the leftover materials can be fully removed at relatively low temperature in the primary sintering process; and after further fine crushing, the materials are conveniently subjected to air flow classification, so that aluminum mixed in the fine crushed materials is efficiently screened out, and the waste lithium iron phosphate powder can be obtained after dry powder iron removal. Based on the steps, a large amount of impurities in the leftover materials are removed in advance, the leftover materials reach a finer granularity, and the waste lithium iron phosphate powder can be calcined at a calcining temperature and a heat preservation time which are lower than those of the prior art in the secondary sintering process, so that the energy consumption is greatly reduced. Meanwhile, after the secondary sintering, the lithium iron phosphate is further refined by airflow crushing, so that impurities in the lithium iron phosphate powder particles overflow along with the crushing of the particles, are removed in the secondary impurity removal process, and are screened to remove iron, and the lithium iron phosphate cathode material with excellent performance can be obtained. Therefore, based on the mutual synergistic effect among the steps, the process designed by the invention can realize the recovery and regeneration of the leftover materials of the positive plate of the lithium iron phosphate battery by the simplest steps with the lowest energy consumption.
(2) The method provided by the invention can directly recycle the leftover materials of the lithium iron phosphate positive plate to regenerate the lithium iron phosphate positive material, and the recycling and regenerating process adopts the conventional industrial production processes of crushing, calcining, impurity removal and the like, so that the method has low requirements on equipment, does not need acid liquid, alkali liquid and other organic solvents, is safe and environment-friendly in the whole process, and is easy for industrial production. Meanwhile, based on the sequence of the steps and the corresponding parameters thereof designed by the invention, the invention only needs to carry out twice calcination, and the temperature and the heat preservation time in the calcination process are both lower, the energy consumption in the whole recycling and regenerating process is low, the cost is low, and the requirements of actual production can be met.
(3) The method provided by the invention can effectively remove impurities from lithium iron phosphate, so that the recycled and regenerated lithium iron phosphate cathode material has excellent performance and no impurity phase, can meet the performance requirements of commercial lithium iron phosphate cathode materials, can completely meet the requirements of mainstream customers at present, and has a good application prospect.
Drawings
Fig. 1 is a schematic flow chart of a method for recovering and regenerating leftover materials of positive plates of lithium iron phosphate batteries, provided by the invention.
Fig. 2 is an XRD pattern of the lithium iron phosphate positive electrode material prepared in example 1.
Fig. 3 is an SEM image of the lithium iron phosphate positive electrode material prepared in example 1.
Fig. 4 is a charge-discharge curve diagram of the lithium iron phosphate positive electrode material prepared in example 1.
Fig. 5 is a graph comparing cycle data of lithium iron phosphate positive electrode materials prepared in example 1 and comparative example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the solution of the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.
In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention provides a method for recycling leftover materials of a positive plate of a lithium iron phosphate battery, which has a process flow shown in figure 1 and comprises the following steps:
s1, coarse crushing: crushing leftover materials to be recovered into coarse particles of 1-10 mm;
s2, first burning: calcining the coarse particles for the first time in an inert atmosphere, and cooling to a preset temperature to obtain a calcined material;
s3, fine crushing: crushing the primary burned material into D 50 Is powder of 2-150 mu m to obtain fine crushed material;
s4, primary impurity removal: carrying out airflow classification on the fine crushed material, and screening out aluminum in the fine crushed material; screening and dry powder iron removal are sequentially carried out to obtain waste lithium iron phosphate powder;
s5, secondary sintering: calcining the waste lithium iron phosphate powder for the second time in an inert atmosphere, and cooling to a preset temperature to obtain a secondary calcined material;
s6, airflow crushing: performing jet milling on the secondary sintering material to obtain lithium iron phosphate fine powder;
s7, secondary impurity removal: sequentially carrying out dry powder iron removal and air flow grading carbon removal on the lithium iron phosphate fine powder to obtain lithium iron phosphate powder;
s8, screening and deironing: and after carrying out vibration screening on the lithium iron phosphate powder, removing iron by using dry powder to obtain the lithium iron phosphate anode material.
In step S2, the calcination temperature of the first calcination is 320-500 ℃, and the heat preservation time is 1-2 h.
In step S5, the calcination temperature of the second calcination is 450-600 ℃, and the heat preservation time is 1-4 h.
In the steps S2 and S5, the inert atmosphere is one or more of nitrogen, argon and helium, and the oxygen content in the inert atmosphere is less than or equal to 1ppm; the predetermined temperature is less than 100 ℃.
In step S4, the vibrating screen used in the screening process is 20 to 40 mesh.
In step S6, D of the lithium iron phosphate fine powder 50 0.6 to 2.0 μm.
In step S7, the carbon content of the lithium iron phosphate powder is 1% to 3%.
In step S8, the vibrating screen used in the vibrating screening process is 40 to 100 mesh.
In steps S4, S7 and S8, the dry powder iron removal process is carried out in a dry powder iron remover with the magnetic induction intensity of more than or equal to 12000 Gs.
The following describes a method for recycling leftover bits and pieces of positive electrode plates of lithium iron phosphate batteries according to the present invention with reference to specific embodiments.
Example 1
The embodiment provides a method for recycling leftover materials of a positive plate of a lithium iron phosphate battery, which has a process flow shown in fig. 1 and specifically comprises the following steps:
s1, coarse crushing: the scrap to be recovered was crushed into coarse particles of 2mm by a crusher.
S2, first burning: loading the coarse particles obtained in the step S1 into a graphite sagger, conveying the graphite sagger into a primary roller furnace through a conveying belt, and performing primary calcination in a nitrogen atmosphere with oxygen content lower than 1ppm; setting the temperature of a heat preservation area in a primary combustion roller bed furnace to be 350 ℃, preserving the heat for 1h, and discharging the material after the material is cooled to 95 ℃ to obtain the primary combustion material.
S3, fine crushing: by means of pulverizersCrushing the calcined material obtained in the step S2 into D 50 Is 80-100 mu m powder to obtain fine crushed material.
S4, primary impurity removal: carrying out airflow classification on the fine crushed material obtained in the step S3 by using an airflow classifier to remove aluminum in the fine crushed material; and then, sieving the fine crushed materials subjected to aluminum removal by using a 20-mesh vibrating screen, and then removing iron by using a dry powder iron remover with the magnetic induction intensity of 12000Gs to obtain waste lithium iron phosphate powder.
S5, secondary sintering: loading the waste lithium iron phosphate powder obtained in the step S4 into a graphite sagger, conveying the sagger into a secondary combustion roller furnace through a conveying belt, and carrying out secondary calcination in a nitrogen atmosphere with the oxygen content lower than 1ppm; setting the temperature of a heat preservation area in the secondary combustion roller bed furnace to be 550 ℃, preserving the heat for 2 hours, and discharging the material after the material is cooled to 95 ℃ to obtain the secondary combustion material.
S6, airflow crushing: airflow crushing is carried out on the secondary combustion material obtained in the step S5 by using an airflow crusher to obtain D 50 1.0 to 1.5 mu m of lithium iron phosphate fine powder;
s7, secondary impurity removal: removing iron from the lithium iron phosphate fine powder obtained in the step S6 by using a dry powder iron remover with magnetic induction intensity of 12000Gs, and removing carbon by using an air classifier to obtain lithium iron phosphate powder with carbon content of 1.4-1.8%;
s8, screening and deironing: and (5) sieving the lithium iron phosphate powder obtained in the step (S6) by a 60-mesh vibrating screen, removing iron by using a dry powder iron remover with the magnetic induction intensity of 12000Gs, and packaging to obtain the finished product lithium iron phosphate cathode material.
XRD test was performed on the lithium iron phosphate positive electrode material prepared in this example, and the result is shown in fig. 2. As can be seen from fig. 1, the diffraction peak of the lithium iron phosphate positive electrode material prepared in this embodiment is consistent with the standard peak of lithium iron phosphate, which indicates that the lithium iron phosphate positive electrode material has no other impurity phase and has a high purity.
Further, SEM test of the lithium iron phosphate positive electrode material prepared in this example was performed, and the result is shown in fig. 3. As can be seen from fig. 3, the surface of the lithium iron phosphate particles prepared in this embodiment is relatively smooth, which indicates that the method provided in this embodiment can effectively remove the binder, carbon powder and other substances attached to the surface of the lithium iron phosphate, and the impurity removal effect is relatively good.
In order to study the physical and chemical properties of the lithium iron phosphate cathode material prepared in this example, the particle size, the compaction density, the specific surface area, and the element content of the lithium iron phosphate cathode material were measured, and compared with the standard of a commercial lithium iron phosphate cathode material, the results are shown in table 1.
Table 1 physicochemical properties of lithium iron phosphate positive electrode material prepared in example 1
As can be seen from table 1, each physical and chemical property of the lithium iron phosphate cathode material prepared in this embodiment can meet the requirement of a commercial lithium iron phosphate cathode material, and can completely meet the requirements of current mainstream customers.
In order to further study the electrical properties of the lithium iron phosphate cathode material prepared in this example, the prepared finished lithium iron phosphate cathode material, SP and PVDF (5130 type) were mixed into a slurry in an N-methylpyrrolidone (NMP) medium according to a mass ratio of 8. Then, a button cell was assembled by using lithium metal as a negative electrode, a polypropylene film as a separator, and LiPF6 (PC + DMC) (1). As can be seen from fig. 4, the battery containing the lithium iron phosphate positive electrode material prepared in this embodiment has good charge and discharge performance, and can meet the requirements of practical applications.
Comparative example 1
Comparative example 1 provides a method for recycling leftover materials of a positive plate of a lithium iron phosphate battery, which is different from the method in example 1 in that step S2 is changed into a method of immersing coarse particles in NMP, stirring for 4 hours, and after powder stripping is completed, blowing and drying for 12 hours at 120 ℃; steps S5 and S6 are deleted, and the remaining steps are the same as those in embodiment 1, and are not described herein again.
In order to compare the performances of the lithium iron phosphate positive electrode materials prepared in example 1 and comparative example 1, the electrochemical performances of the full cells prepared therefrom were respectively tested, and the results are shown in table 2.
Table 2 comparison of full cell data of lithium iron phosphate positive electrode materials prepared in example 1 and comparative example 1
As can be seen from table 2, compared with comparative example 1, the lithium iron phosphate positive electrode material prepared in example 1 has lower internal resistance and higher voltage, can achieve higher charge capacity and discharge capacity, and has significantly higher charge-discharge efficiency.
The cycle performance of the lithium iron phosphate positive electrode materials prepared in example 1 and comparative example 1 was further tested, and the results are shown in fig. 5. As can be seen from fig. 5, the lithium iron phosphate positive electrode material prepared in example 1 has significantly better cycle performance, and has a relatively higher capacity retention rate under the same cycle number.
As can be seen from the comprehensive table 2 and fig. 5, compared with the impregnation with NMP, the two calcinations in step S2 and step S5 in example 1 can not only avoid the emission of harmful solvents, but also effectively improve the electrochemical performance of the prepared lithium iron phosphate cathode material.
Examples 2 to 11 and comparative examples 2 to 5
Examples 2 to 11 and comparative examples 2 to 5 each provide a method for recycling leftover materials of positive electrode sheets of lithium iron phosphate batteries, which is different from example 1 in that the calcining temperature and the holding time in step S2 and step S5 are changed, and the remaining steps are the same as example 1, and are not repeated herein. The calcination temperature and the holding time for each example are shown in Table 3.
TABLE 3 calcination temperatures and holding times in steps S2 and S5 in examples 2 to 11 and comparative examples 2 to 5
Button cells were prepared from the lithium iron phosphate positive electrode materials prepared in examples 2 to 11 and comparative examples 2 to 5 in the manner described in example 1, and the first charge capacity, the first discharge capacity, and the first charge-discharge efficiency of the button cells containing the lithium iron phosphate positive electrode materials prepared in examples 1 to 11 and comparative examples 2 to 5 were measured at 0.1C, and the results are shown in table 4.
Table 4 button cell data of lithium iron phosphate positive electrode materials prepared in examples 1 to 11 and comparative examples 2 to 5
As can be seen from table 4, the changes in the temperature and the holding time of the two calcinations in step S2 and step S5 have a great influence on the performance of the prepared lithium iron phosphate cathode material.
It can be seen by comparing examples 1 to 5 with comparative examples 2 to 3 that properly increasing the calcination temperature or prolonging the heat preservation time in step S2 within a certain range is beneficial to improving the electrochemical performance of the lithium iron phosphate positive electrode material, but when the calcination temperature in step S2 reaches 500 ℃, the temperature is continuously increased to 600 ℃, the charge capacity and the discharge capacity of the prepared lithium iron phosphate positive electrode material are both significantly reduced, and the first charge-discharge efficiency is also reduced. Therefore, the temperature of the first calcination is preferably 320-500 ℃, and the holding time is preferably 1-2 h.
Further comparing examples 1, 7 to 11 and 4 to 5, it can be seen that properly increasing the calcination temperature or prolonging the temperature holding time in step S5 within a certain range is beneficial to improving the electrochemical performance of the lithium iron phosphate positive electrode material, and when the temperature in step S5 is lower than 450 ℃, the charge capacity, the discharge capacity and the first charge-discharge efficiency of the prepared lithium iron phosphate positive electrode material are all significantly reduced. And when the temperature in the step S5 reaches 600 ℃, the temperature is continuously raised to 700 ℃, so that the energy consumption is obviously increased, and the charge and discharge capacity and the first charge and discharge efficiency of the prepared lithium iron phosphate cathode material are also reduced. Therefore, the temperature of the second calcination is preferably 450-600 ℃, and the heat preservation time is 1-4 h, under the condition, the electrochemical performance of the prepared lithium iron phosphate anode material can be effectively improved with lower energy consumption, so that the lithium iron phosphate anode material can reach the commercial standard, and the requirement of practical application can be met.
It should be noted that, in step S1, the size of the coarse particles obtained after crushing may be 1 to 10mm; in step S3, D of the finely divided material obtained after crushing 50 Can be 2 to 150 μm; in steps S2 and S5, the inert atmosphere may be one or more of nitrogen, argon, helium; in step S4, the mesh number of the vibrating screen used in the screening process may be 20 to 40 meshes; in step S6, D of the lithium iron phosphate fine powder 50 May be 0.6 to 2.0 μm; in step S8, the mesh number of the vibrating screen used in the vibrating screening process may be 40 to 100 meshes, which all belong to the protection scope of the present invention.
In conclusion, the invention provides a method for recycling leftover materials of a positive plate of a lithium iron phosphate battery. The method comprises the following steps: firstly, crushing leftover materials into coarse particles, then calcining the coarse particles in an inert atmosphere, crushing the materials into fine materials after the materials are cooled, and removing impurities through air flow classification and dry powder iron removal processes to obtain waste lithium iron phosphate powder; and calcining the waste lithium iron phosphate powder in an inert atmosphere, cooling the material, performing jet milling to obtain fine lithium iron phosphate powder, and performing secondary impurity removal and screening to remove iron to obtain the lithium iron phosphate anode material. Through the mode, the method can reduce the temperature and time required by the calcining process by utilizing the synergistic effect among the steps, and effectively remove impurities in the lithium iron phosphate, so that the leftover materials of the positive plate of the lithium iron phosphate battery can be recycled by the simplest step, the lowest energy consumption and a safe and environment-friendly production mode, and the lithium iron phosphate positive material with excellent performance is obtained, so that the requirement of practical application is met.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.
Claims (6)
1. A method for recycling leftover materials of positive plates of lithium iron phosphate batteries is characterized by comprising the following steps:
s1, coarse crushing: crushing leftover materials to be recovered into coarse particles of 1-10 mm;
s2, first burning: calcining the coarse particles for the first time in an inert atmosphere, and cooling to a preset temperature to obtain a calcined material; the calcination temperature of the first calcination is 320-500 ℃, and the heat preservation time is 1-2 h;
s3, fine crushing: crushing the primary burned material into D 50 Is powder of 2-150 mu m to obtain fine crushed material;
s4, primary impurity removal: carrying out airflow classification on the fine crushed material, and screening out aluminum in the fine crushed material; then screening and dry powder deironing are sequentially carried out to obtain waste lithium iron phosphate powder; the vibrating screen used in the screening process is 20-40 meshes;
s5, secondary sintering: calcining the waste lithium iron phosphate powder for the second time in an inert atmosphere, and cooling to a preset temperature to obtain a secondary calcined material; the calcination temperature of the second calcination is 450-600 ℃, and the heat preservation time is 1-4 h;
s6, airflow crushing: performing jet milling on the secondary sintering material to obtain lithium iron phosphate fine powder; d of the lithium iron phosphate fine powder 50 0.6-2.0 μm;
s7, secondary impurity removal: sequentially carrying out dry powder iron removal and air flow grading carbon removal on the lithium iron phosphate fine powder to obtain lithium iron phosphate powder;
s8, screening and deironing: and after carrying out vibration screening on the lithium iron phosphate powder, removing iron by using dry powder to obtain the lithium iron phosphate cathode material.
2. The method for recycling leftover materials of positive plates of lithium iron phosphate batteries according to claim 1, characterized by comprising the following steps: in the steps S2 and S5, the inert atmosphere is one or more of nitrogen, argon and helium, and the oxygen content in the inert atmosphere is less than or equal to 1ppm.
3. The method for recycling the leftover materials of the positive plate of the lithium iron phosphate battery according to claim 1, wherein the method comprises the following steps: in steps S2 and S5, the predetermined temperature is below 100 ℃.
4. The method for recycling the leftover materials of the positive plate of the lithium iron phosphate battery according to claim 1, wherein the method comprises the following steps: in step S7, the carbon content of the lithium iron phosphate powder is 1% to 3%.
5. The method for recycling the leftover materials of the positive plate of the lithium iron phosphate battery according to claim 1, wherein the method comprises the following steps: in step S8, the vibrating screen used in the vibrating screening process is 40 to 100 mesh.
6. The method for recycling the leftover materials of the positive plate of the lithium iron phosphate battery according to claim 1, wherein the method comprises the following steps: in steps S4, S7 and S8, the dry powder iron removal process is carried out in a dry powder iron remover with the magnetic induction intensity of more than or equal to 12000 Gs.
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Denomination of invention: A recycling and regeneration method for scraps of positive electrode plates in lithium iron phosphate batteries Granted publication date: 20221125 Pledgee: Guanggu Branch of Wuhan Rural Commercial Bank Co.,Ltd. Pledgor: WUHAN RUIKEMEI NEW ENERGY Co.,Ltd. Registration number: Y2024980018586 |