CN118281394A - Method for recycling active material reclaimed materials from positive plate - Google Patents
Method for recycling active material reclaimed materials from positive plate Download PDFInfo
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- CN118281394A CN118281394A CN202410702960.6A CN202410702960A CN118281394A CN 118281394 A CN118281394 A CN 118281394A CN 202410702960 A CN202410702960 A CN 202410702960A CN 118281394 A CN118281394 A CN 118281394A
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- iron phosphate
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- 239000011149 active material Substances 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title claims abstract description 36
- 239000000463 material Substances 0.000 title claims abstract description 32
- 238000004064 recycling Methods 0.000 title claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 23
- 230000001590 oxidative effect Effects 0.000 claims abstract description 23
- 239000007800 oxidant agent Substances 0.000 claims abstract description 22
- 239000006258 conductive agent Substances 0.000 claims abstract description 17
- 239000000110 cooling liquid Substances 0.000 claims abstract description 15
- 239000000843 powder Substances 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 11
- 239000000203 mixture Substances 0.000 claims abstract description 11
- 238000000926 separation method Methods 0.000 claims abstract description 10
- 238000007873 sieving Methods 0.000 claims abstract description 7
- 238000002791 soaking Methods 0.000 claims abstract description 7
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 7
- 230000001105 regulatory effect Effects 0.000 claims abstract description 6
- 239000000706 filtrate Substances 0.000 claims abstract description 5
- 239000007788 liquid Substances 0.000 claims abstract description 5
- 239000007790 solid phase Substances 0.000 claims abstract description 5
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 55
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical group [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 10
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 9
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 9
- 239000003623 enhancer Substances 0.000 claims description 6
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 claims description 6
- 239000002826 coolant Substances 0.000 claims description 5
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 5
- 239000011790 ferrous sulphate Substances 0.000 claims description 5
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 3
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims description 3
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 3
- 229910052744 lithium Inorganic materials 0.000 claims description 3
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims description 3
- 239000002245 particle Substances 0.000 abstract description 58
- 239000011230 binding agent Substances 0.000 abstract description 18
- 239000012535 impurity Substances 0.000 abstract description 11
- 229910052751 metal Inorganic materials 0.000 abstract description 11
- 239000002184 metal Substances 0.000 abstract description 11
- 238000011084 recovery Methods 0.000 abstract description 9
- 230000000052 comparative effect Effects 0.000 description 35
- 239000002033 PVDF binder Substances 0.000 description 29
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 12
- 229910052799 carbon Inorganic materials 0.000 description 11
- 238000001816 cooling Methods 0.000 description 11
- 239000000853 adhesive Substances 0.000 description 9
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- 239000007774 positive electrode material Substances 0.000 description 8
- 238000000197 pyrolysis Methods 0.000 description 8
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 7
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- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
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- 150000002500 ions Chemical class 0.000 description 3
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910000805 Pig iron Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
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Abstract
The invention relates to a method for recycling active material reclaimed materials from positive plates. The recovery method of the invention comprises the following steps: regulating the charge of the battery to 0% of SOC, disassembling the positive plate, and performing heat treatment on the positive plate; transferring the positive plate after heat treatment to low-temperature cooling liquid containing an oxidant for soaking and ultrasonic treatment within 1min, and carrying out solid-liquid separation to obtain a filtrate, a powder mixture and a current collector; and (3) carrying out centrifugal separation on the powder mixture, removing the upper conductive agent, drying, crushing and sieving the solid phase obtained by centrifugal separation to obtain the active material reclaimed material. The active material reclaimed material of the reclaimed positive plate still has high gram capacity and keeps good cycle performance. The active material reclaimed material removes conductive agent, binder, broken active material micropowder and organic impurities, and the obtained reclaimed material has low metal impurity content, high purity and uniform particle size distribution.
Description
Technical Field
The invention relates to the technical field of battery material recovery, in particular to a method for recovering active material recovery materials from positive plates.
Background
The positive electrode sheet of a battery is made by coating a positive electrode active material layer on a metal foil, which is referred to in the industry as a current collector, and functions to collect and conduct current, and the positive electrode active material layer generally contains a positive electrode active material, a conductive agent, a binder or other functional additives, wherein the binder functions to enable the positive electrode active material and other additives to adhere to the surface of the current collector.
In the prior art, in the recovery method of the battery anode active material, after a battery core is disassembled to obtain an anode plate, the anode plate is crushed by a crusher, and then the active material layer and a metal foil (current collector) are stripped by washing with strong acid to obtain a recovery material; there are also recovery methods that do not use crushed pole pieces, but a method of removing a binder by pyrolysis to peel an active material layer and a metal foil (current collector).
The two methods have corresponding disadvantages: (1) When the mechanical crushing method is used for recycling, more magnetic impurities are introduced into the crushing process of the crusher, for example, the current collector is crushed and mixed into the recycled material, and meanwhile, the crusher can produce metal impurities such as pig iron, nickel, zinc and the like to be mixed into the recycled material due to friction and abrasion, so that the recycled material needs to be subjected to a complicated demagnetizing process. And secondly, a binder PVDF (polyvinylidene fluoride) in the positive electrode active material layer is attached to the surfaces of active material particles, and the positive electrode active material layer and the current collector cannot be well separated in the crushing process, so that after the positive electrode plate is crushed, the binder PVDF and the like are not completely separated from the surface of the positive electrode active material, and the conductivity and the gram capacity are poor when the active material reclaimed materials are reused. The reclaimed materials contain more fine powder, carbon black and other conductive agent components, multiple screening treatments are needed, the procedures are more, and the time consumption is long. (2) The method for removing the binder through pyrolysis is characterized in that PVDF is a fluorine-containing polymer, and some carbide remains during pyrolysis (especially under the condition of insufficient air during pyrolysis), and the PVDF is tightly wrapped on the surfaces of active material particles in the positive plate, so that PVDF cannot be effectively stripped, and the conductivity of the recovered active material can be influenced. In addition, the existing high-temperature pyrolysis technology needs high temperature, at least higher than 300 ℃, long pyrolysis time and high energy consumption, and extremely toxic gases such as hydrogen cyanide and the like are generated in the process; temperatures below 300 ℃ are not pyrolyzable. In summary, it is known that the recovery of active material with high purity and uniform size can be obtained only by removing the binder as much as possible.
There is therefore an urgent need to provide a simple and efficient method for recycling active materials from positive electrode sheets.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for recycling active material reclaimed materials from positive plates.
The invention aims to provide a method for recycling active material reclaimed materials from a positive plate, which comprises the following steps:
(1) Regulating the battery to 0% of SOC, disassembling the positive plate, and performing heat treatment on the positive plate;
(2) Transferring the positive plate after heat treatment into low-temperature cooling liquid containing an oxidant for soaking and ultrasonic treatment within 1min, and carrying out solid-liquid separation to obtain a filtrate, a powder mixture and a current collector;
(3) And centrifugally separating the powder mixture, removing the upper undissolved organic matter conductive agent, drying, crushing and sieving the solid phase obtained by centrifugal separation to obtain the active material reclaimed material.
In some embodiments of the present invention, in the step (1), the temperature of the heat treatment is 180-230 ℃ and the time is 10-30 min; the active material of the positive plate comprises one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium cobaltate and lithium nickel cobalt manganate.
In some embodiments of the invention, in step (2), the oxidant-containing sub-cooling fluid is selected from one or more of NMP, DMAc, DMF, TEP and DMSO.
In some embodiments of the invention, in step (2), the oxidizing agent is selected from hydrogen peroxide and/or potassium dichromate.
In some embodiments of the invention, the oxidizing agent further comprises an oxidizing enhancer, wherein the oxidizing enhancer is a ferrous salt.
In some embodiments of the invention, the ferrous salt is selected from ferrous sulfate and/or ferrous chloride.
In some embodiments of the present invention, in the step (2), the temperature of the low-temperature coolant containing the oxidant is 0 to-35 ℃.
In some embodiments of the present invention, in the step (2), the soaking time is 1 to 3 hours.
In some embodiments of the present invention, in the step (3), the drying temperature is 100-140 ℃ and the drying time is 30 min-1.5 h.
In some embodiments of the invention, in step (3), the mesh size of the screen is 10-200 nm.
Compared with the prior art, the technical scheme of the invention has the following advantages:
(1) According to the recovery method, the current collector and the active material layer are not required to be separated in a pole piece crushing mode, so that metal impurities are prevented from being introduced, and the active material recovery material is not required to be subjected to demagnetization treatment. But ensures that the adhesive on the positive plate is separated from the current collector through rapid high-temperature and low-temperature treatment, and can be applicable to various adhesives, such as PVA, PTFE, PVDF and the like. The recycling method used by the invention can also be suitable for the anode materials of various batteries, such as lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium cobaltate, lithium nickel cobalt manganate and other material systems.
(2) The surface of the active material reclaimed material in the reclaimed positive plate is not wrapped by the adhesive, the electrical property of the active material reclaimed material is not affected, and the reclaimed positive plate has high gram capacity and good cycle performance. The active material reclaimed material removes conductive agents such as conductive carbon black, broken active material micropowder and organic impurities, and the obtained active material reclaimed material has low metal impurity content, high purity and uniform particle size distribution.
Detailed Description
In order to solve the technical problems pointed out in the background art, the invention achieves the purposes of the invention through the following scheme:
The invention provides a method for recycling active material reclaimed materials from a positive plate, which comprises the following steps:
(1) Regulating the battery to 0% of SOC, disassembling the positive plate, and performing heat treatment on the positive plate;
(2) Transferring the positive plate after heat treatment into low-temperature cooling liquid containing an oxidant for soaking and ultrasonic treatment within 1min, and carrying out solid-liquid separation to obtain a filtrate, a powder mixture and a current collector;
(3) And centrifugally separating the powder mixture, removing the upper conductive agent, drying, crushing and sieving the solid phase obtained by centrifugal separation to obtain the active material reclaimed material.
In the invention, in the step (3), after the centrifugation, since the particle size (nano-scale) of the conductive agent is much smaller than the particle size (micro-scale) of the active material, and the mass is lighter, most of the conductive agent is positioned on the upper layer of the powder mixture after the centrifugation, and is directly removed. For a small portion of the conductive agent mixed in the solid phase, it is removed by a screen sieving treatment.
In the specific embodiment of the present invention, in the step (1), the temperature of the heat treatment is 180-230 ℃, and may be, for example, 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, 215 ℃, 220 ℃, 225 ℃, 230 ℃ or any interval value between any two values, when the temperature of the heat treatment is too low, the softening point of PVDF cannot be reached, and when the temperature is too high, the adhesive on the pole piece is in a softened state, but the energy consumption is high, and the cost is high; the time is 10-30 min, and may be, for example, 10min, 15min, 20min, 25min, 30min, etc. The heat treatment operation is carried out in normal air atmosphere without special equipment.
In the invention, in the step (1), the disassembled positive plate is not subjected to mechanical crushing, and if the positive plate is crushed in advance, the difficulty in separating the binder (such as PVDF) and the current collector is greatly increased.
In the invention, in the step (1), active ions are taken off from active materials in the positive plate and then are embedded into the active materials in the negative plate when the battery is charged in the whole process of regulating the battery to 0% SOC; when the battery is discharged, active ions are taken off from the active material in the negative electrode plate and then are embedded back into the active material in the positive electrode plate, so that the purpose of regulating the charge of the battery to 0% SOC is to enable the active ions embedded in the negative electrode plate to return to the positive electrode plate, and the subsequent collection treatment of the active material in the positive electrode plate is facilitated.
In a specific embodiment of the present invention, in step (2), the low-temperature cooling liquid containing the oxidizing agent is selected from one or more of NMP, DMAc, DMF, TEP and DMSO.
In the specific embodiment of the invention, in the step (2), the temperature of the low-temperature cooling liquid containing the oxidant is 0 to minus 35 ℃.
In a specific embodiment of the present invention, in step (2), the oxidizing agent is selected from hydrogen peroxide and/or potassium dichromate.
In a specific embodiment of the present invention, the oxidizing agent further includes an oxidizing enhancer, and the oxidizing enhancer is a ferrite. In order to further destroy the binding effect of the binder (such as PVDF), a strong oxidant can be added into the low-temperature cooling liquid, the strong oxidant and the functional groups of the binder are subjected to oxidation reaction, the binding effect of the binder is further destroyed, and the oxidizing property of the oxidizing solution can be greatly enhanced by adding ferrous ions into the strong oxidant, so that the effect is better.
In the specific embodiment of the present invention, the ferrous salt can achieve the object of the present invention as long as it contains ferrous ions, and the oxidizing property of the oxidizing agent is enhanced by the ferrous ions, so that a substance containing ferrous ions can be selected, and ferrous sulfate and/or ferrous chloride and the like can be preferred.
In the invention, the adhesive on the positive plate can be separated from the current collector through rapid (within 1 min) high-temperature-low-temperature treatment. Here, rapid-high temperature-cooling, three conditions are indispensable. Because the high-temperature heat treatment can soften the adhesive and then rapidly cool the adhesive, strong thermal stress can be generated in the temperature rapid change process, so that the adhesive force between the adhesive and the active material in the positive plate is invalid. The invention also carries out ultrasonic treatment on the low-temperature cooling liquid, and the ultrasonic treatment can be cooperated with high-temperature heat treatment to promote the stripping of the binder and the current collector, and can also promote the dissolution of the binder (such as PVDF) in the cooling liquid, thereby realizing the efficient removal of the binder.
In a specific embodiment of the invention, in step (2), the binder is removed to the greatest extent possible by solid-liquid separation.
In the embodiment of the invention, in the step (2), the soaking time is 1-3 hours.
In the embodiment of the invention, in the step (3), the drying temperature is 100-140 ℃ and the drying time is 30 min-1.5 h.
In the specific embodiment of the invention, in the step (3), the pore diameter of the screened screen is 10-200 nm. The redundant conductive agent powder and the tiny crushed active material in the material can be removed through sieving, so that the pure active material reclaimed material with uniform particle size is obtained.
The present invention will be further described with reference to specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the present invention and practice it.
The specific conditions of the lithium iron phosphate battery used in the embodiment of the invention are as follows: the battery core of the lithium iron phosphate battery is formed by winding a positive plate, a diaphragm and a negative plate. The positive plate is prepared by coating positive electrode slurry on two sides of an aluminum foil, wherein the positive electrode slurry comprises a positive electrode active material (lithium iron phosphate), a conductive agent (conductive carbon black) and a binder (PVDF) in a mass ratio of 97.5:1.4:1.2, the solvent is N-methyl-2-pyrrolidone. The negative plate is prepared by coating negative electrode slurry on the two sides of a copper foil, wherein the negative electrode slurry comprises a negative electrode active material (graphite), a conductive agent (ketjen black) and a binder (PVDF), and the mass ratio is 96.2:2:1.8, the solvent is deionized water. The separator was a 9 μm thick polyethylene separator. Wherein, the particle diameter D50 of the lithium iron phosphate material is 1.5um, and the D50 of the conductive carbon black is 45nm.
Example 1
The embodiment provides a method for recycling lithium iron phosphate from a positive plate, which comprises the following steps:
Step 1: discharging the lithium iron phosphate battery to a state of 2.0V discharging, and then disassembling the positive and negative plates and the diaphragm to obtain the positive plate.
Step 2: and in the air atmosphere, the positive plate is placed into a high-temperature furnace to be heated, wherein the heating temperature is 200 ℃, and the heating time is 20min.
Step 3: and (3) transferring the positive plate prepared in the step (2) into a low-temperature cooling liquid in 2 seconds, wherein the temperature of the low-temperature cooling liquid is minus 20 ℃, the cooling time is 2 hours, and simultaneously, adding ultrasonic treatment to obtain a mixture A. Wherein, the low-temperature cooling liquid contains strong oxidant (ferrous sulfate and hydrogen peroxide solution, 10 parts of ferrous sulfate and 20 parts of hydrogen peroxide solution, wherein the volume concentration of each part of hydrogen peroxide solution is 70 percent by weight).
Step 4: and (3) filtering the mixture A obtained in the step (3) to obtain filtrate mixed solution B and filter residue insoluble matter C, wherein the mixed solution B contains a small amount of conductive agent and PVDF dissolved in cooling liquid by using a strong oxidant, and the insoluble matter C contains lithium iron phosphate particles and conductive agent. And (3) centrifugally separating the mixed solution B to remove fine conductive agent powder with lighter upper layer weight. And (3) drying the insoluble matters C at 120 ℃ for 1h, crushing by using an air flow mill, and then sieving with a sieve with the aperture of 160nm, wherein residues on the sieve are obtained lithium iron phosphate particle reclaimed materials with the particle size of 0.2-5 mu m.
Example 2
Unlike example 1, in step 2, the heating temperature was 180℃and the heating time was 10 minutes, with the remaining conditions being the same.
Example 3
Unlike example 1, in step 2, the heating temperature was 230℃and the heating time was 30min, with the remaining conditions being the same.
Example 4
Unlike example 1, in step 3, the positive electrode sheet produced in step 2 was transferred into a low-temperature coolant within 10 seconds, and the remaining conditions were the same.
Example 5
Unlike example 1, in step 3, the cooling time was 1h, and the remaining conditions were the same.
Example 6
Unlike example 1, in step 3, the cooling time was 3h, and the remaining conditions were the same.
Example 7
Unlike example 1, in step 3, the cooling temperature was 0℃and the other conditions were the same.
Example 8
Unlike example 1, in step 3, the cooling temperature was-35℃and the other conditions were the same.
Comparative example 1
Unlike example 1, in step 2, the heating temperature was 310 ℃, and the other conditions were the same.
Comparative example 2
Unlike example 1, in step 2, the heating temperature was 170℃and the other conditions were the same.
Comparative example 3
Unlike example 1, in step 3, the positive electrode sheet produced in step 2 was transferred to a low-temperature coolant at 30min, and the other conditions were the same.
Comparative example 4
Unlike example 1, in step 3, the cooling time was 30min, and the remaining conditions were the same.
Comparative example 5
Unlike example 1, in step 3, the cooling temperature was 10℃and the other conditions were the same.
Comparative example 6
Unlike example 1, in step 1, the positive electrode sheet was crushed using a crusher.
The lithium iron phosphate particles obtained in each of the above examples and comparative examples were subjected to characterization tests for particle diameter, metal impurities and carbon content, and these lithium iron phosphate particles were prepared into button half cells, respectively, and performance tests were performed, and the test results are shown in table 1.
TABLE 1
。
Analysis of results:
Example 1 in comparison with comparative examples 1-2, the D50 and carbon content of the lithium iron phosphate particles of comparative examples 1-2 are significantly higher than those of the lithium iron phosphate particles of example 1, because: (1) Comparative example 1 uses a higher treatment temperature, while PVDF is a fluoropolymer, and some char remains during pyrolysis (especially in the case of insufficient air during pyrolysis), and is tightly packed on the surface of lithium iron phosphate particles, so that the D50 of the lithium iron phosphate particles is shown to be large (i.e., D50 is greater than 1.5 um) and the carbon content is high. Moreover, since the carbide is tightly wrapped on the surface of the lithium iron phosphate particles, the conductivity of the lithium iron phosphate particles is deviated, as can be seen from the smaller cycle number of the button cell prepared from the lithium iron phosphate particles of comparative example 1; (2) The treatment temperature of comparative example 2 was too low, the softening point of PVDF was not reached, PVDF was still present on the surface of the lithium iron phosphate particles, resulting in the lithium iron phosphate particles D50 of comparative example 2 being larger and lower in conductivity, and the number of cycles of the prepared button cell was smaller.
The D50 and carbon content of the lithium iron phosphate particles of comparative example 3 are significantly higher than those of example 1, as compared to comparative example 3, because: in comparative example 3, no "rapid cooling" was achieved, and the temperature change process did not produce sufficient strong thermal stress to effectively disable the binding force of PVDF and lithium iron phosphate particles; and, the surface of the lithium iron phosphate particles is adhered with conductive carbon black due to the existence of PVDF binding force, so that the high carbon content is represented. The increase in the number of cycles of the button cell produced by the lithium iron phosphate particles of comparative example 3 compared to comparative example 1 indicates that the conductivity of the lithium iron phosphate particles of comparative example 3 is increased compared to comparative example 1, but that the conductivity of the lithium iron phosphate particles of comparative example 3 is still significantly lower than that of the lithium iron phosphate particles of example 1.
Example 1 compared to comparative example 4, the D50 and carbon content of the lithium iron phosphate particles of comparative example 4 are significantly higher than those of the lithium iron phosphate particles of example 1, because: the cooling time of comparative example 4 was insufficient, PVDF was not sufficiently dissolved in the cooling liquid having strong oxidizing property, and lithium iron phosphate particles were not completely peeled off from PVDF. And, the surface of the lithium iron phosphate particles is adhered with conductive carbon black due to the existence of PVDF binding force, so that the high carbon content is represented. The significantly lower number of cycles of the button cell made with the lithium iron phosphate particles of comparative example 4 compared to the lithium iron phosphate particles of example 1 indicates that the lithium iron phosphate particles of comparative example 4 have a lower conductivity, and the lithium iron phosphate particles do not completely delaminate from the PVDF, resulting in a low purity of the lithium iron phosphate particles, affecting the conductivity thereof.
Example 1 compared to comparative example 5, the D50 and carbon content of the lithium iron phosphate particles of comparative example 5 are significantly higher than those of the lithium iron phosphate particles of example 1, because: the cooling temperature of comparative example 5 was insufficient, PVDF was not sufficiently dissolved in a cooling liquid having strong oxidizing property, and lithium iron phosphate particles were not completely peeled off from PVDF. And, the surface of the lithium iron phosphate particles is adhered with conductive carbon black due to the existence of PVDF binding force, so that the high carbon content is represented. The significantly lower number of cycles of the button cell made with the lithium iron phosphate particles of comparative example 5 compared to the lithium iron phosphate particles of example 1 indicates that the lithium iron phosphate particles of comparative example 5 have lower conductivity, and the purity of the lithium iron phosphate particles is not high due to incomplete exfoliation of the lithium iron phosphate particles from PVDF, affecting the conductivity.
The metal impurity content of comparative example 6 is far superior to that of example 1 compared with comparative example 6 because: the positive plate is crushed in advance, the difficulty of separating the active material layer from the foil is increased, and metal impurity particles are mixed in recovered obtained lithium iron phosphate particles; the button cell prepared in comparative example 6 has a much lower number of cycles than in example 1 because the metal impurity particles are mixed in the lithium iron phosphate particles, reducing the conductivity of the lithium iron phosphate particles; the D50 and carbon content of the lithium iron phosphate particles of comparative example 6 are significantly higher than example 1 because the lithium iron phosphate particles are not completely exfoliated from the PVDF, and the surfaces of the lithium iron phosphate particles are adhered with conductive carbon black due to the presence of PVDF adhesion, thus exhibiting a higher carbon content; however, since the lithium iron phosphate particles are not completely peeled off from the PVDF, resulting in the influence of the conductivity of the lithium iron phosphate particles, the resulting button cell exhibits a lower number of cycles.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. A method for recycling active material recycling material from a positive electrode sheet, comprising the steps of:
(1) Regulating the battery to 0% of SOC, disassembling the positive plate, and performing heat treatment on the positive plate;
(2) Transferring the positive plate after heat treatment into low-temperature cooling liquid containing an oxidant for soaking and ultrasonic treatment within 1min, and carrying out solid-liquid separation to obtain a filtrate, a powder mixture and a current collector;
(3) And centrifugally separating the powder mixture, removing the upper conductive agent, drying, crushing and sieving the solid phase obtained by centrifugal separation to obtain the active material reclaimed material.
2. The method according to claim 1, wherein in the step (1), the heat treatment is performed at 180-230 ℃ for 10-30 min;
the active material of the positive plate comprises one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium cobaltate and lithium nickel cobalt manganate.
3. The method of claim 1, wherein in step (2), the low temperature coolant comprising an oxidizing agent is selected from one or more of NMP, DMAc, DMF, TEP and DMSO.
4. The method according to claim 1, wherein in step (2), the oxidizing agent is selected from hydrogen peroxide and/or potassium dichromate.
5. The method of claim 4, wherein the oxidizing agent further comprises an oxidizing enhancer, and wherein the oxidizing enhancer is a ferrous salt.
6. The method of claim 5, wherein the ferrous salt is selected from ferrous sulfate and/or ferrous chloride.
7. The method according to claim 1, wherein in the step (2), the temperature of the low-temperature coolant containing the oxidizing agent is 0 to-35 ℃.
8. The method of claim 1, wherein in step (2), the soaking time is 1 to 3 hours.
9. The method of claim 1, wherein in the step (3), the drying temperature is 100-140 ℃ and the drying time is 30 min-1.5 h.
10. The method according to claim 1, wherein in the step (3), the mesh size of the sieve is 10 to 200nm.
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| Publication Number | Publication Date |
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| CN118281394A true CN118281394A (en) | 2024-07-02 |
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