CN116136022A - Stripping agent, stripping liquid composition and stripping method of waste lithium-ion battery electrode materials - Google Patents
Stripping agent, stripping liquid composition and stripping method of waste lithium-ion battery electrode materials Download PDFInfo
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- CN116136022A CN116136022A CN202111372326.3A CN202111372326A CN116136022A CN 116136022 A CN116136022 A CN 116136022A CN 202111372326 A CN202111372326 A CN 202111372326A CN 116136022 A CN116136022 A CN 116136022A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/10—Other heavy metals
- C23G1/103—Other heavy metals copper or alloys of copper
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/12—Light metals
- C23G1/125—Light metals aluminium
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/54—Reclaiming serviceable parts of waste accumulators
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Abstract
The invention provides a stripping agent, a stripping liquid composition and a stripping method of waste lithium ion battery electrode materials. The stripping agent comprises organic acid, acid salt of phosphoric acid and corrosion inhibitor, wherein the organic acid is one or more selected from oxalic acid, succinic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, citric acid, maleic acid and fumaric acid; the acid salt of phosphoric acid is selected from one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate and potassium dihydrogen phosphate; the corrosion inhibitor is one or more selected from sodium salt, potassium salt, ammonium salt, mercaptan, thiourea, boric acid and nicotinic acid. When the stripping agent is subsequently applied to a battery stripping process, the stripping accuracy is higher, the reaction is milder, the stripping effect is better, the positive electrode material, the negative electrode material, the copper foil and the aluminum foil can be effectively separated under the controllable condition, and each component has higher recovery rate, especially the positive electrode material and the negative electrode material.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to a stripping agent, a stripping liquid composition and a stripping method of waste lithium ion battery electrode materials.
Background
In the prior stripping technology, a plurality of researchers adopt a method of dissolving the adhesive by using an organic solvent and then assist other means, such as ultrasonic, mechanical stirring, heating and the like, to achieve the stripping of the electrode material in the waste battery. However, the use of the organic solvent causes the copper-aluminum foil obtained by stripping to carry a large amount of organic solvent, the subsequent treatment is troublesome, a large amount of organic waste liquid and organic waste gas can be generated, the organic solvent is usually expensive, the obtained anode and cathode materials are mixed materials, and the stripping cost of the method is higher, and the anode and cathode materials are difficult to sort. There are also methods for corrosion of aluminum foil by sodium hydroxide by some researchers, stripping and recovering the positive electrode material, the method is intense in reaction, hydrogen is generated, the aluminum foil is usually corroded completely, the method has a large amount of waste water, the aluminum foil cannot be effectively recovered, and the separation and recovery of the negative electrode material and the copper foil cannot be ensured.
For example, in the prior art: CN105811038A uses alkali to strip the positive electrode and uses water to strip the negative electrode, and auxiliary ultrasound is added, so that the stripping time is long, and the electrolyte is not fully recovered. CN109193064a uses a pyrolysis method to carbonize the binder to separate the positive electrode material from the aluminum foil, which consumes much energy and generates toxic gases, requiring additional equipment for tail gas treatment. CN109713393a uses a mixed organic solvent to strip the electrode material, and auxiliary heat and ultrasound are performed to improve the stripping effect in the stripping process, and the stripping period is longer, the negative graphite and the positive electrode material are not separated, and the subsequent treatment process is complex. And the organic solvent attached to the copper-aluminum foil after stripping is difficult to treat, so that a large amount of organic waste liquid and waste gas are generated, and the environmental impact is large. In the CN106505271a patent, it is mentioned that the positive electrode material is peeled off by heating step by step in an inert gas environment or in air and then soaking in sodium hydroxide solution, the treatment time is long, the energy consumption is required for heating and heat preservation, and the equipment cost is increased. JP2019521485a discloses a method of separating a current collector and an electrode active material by dissolving a binder material under mechanical agitation using a polar solvent after cutting a lithium ion battery into pieces. Wherein the polar solvent includes, but is not limited to, a buffer solution of a salt of the group: lithium carbonate, lithium bicarbonate, lithium phosphate, sodium carbonate, sodium bicarbonate, sodium phosphate, potassium carbonate, potassium bicarbonate, potassium phosphate, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, and combinations thereof. However, this method cannot effectively treat the electrolyte. The prior art patents related to electrolyte recovery, such as CN103825065B, are directed to electrolyte recovery alone, which describes a method for collecting electrolyte by cryogenic freezing after battery disassembly. However, the method for recycling the electrolyte makes the recycling process of the lithium battery complex and has high cost. CN103035977a describes that the aluminum foil is etched and dissolved by potassium hydroxide solution, so that only the positive electrode material remains, the reaction is intense, all aluminum foil reacts with the stripping solution, and the recovery of aluminum in the stripping solution also generates waste water and consumes new reagents.
Of course, there are also some patents that choose to recover the positive electrode material using an acidic stripping agent, for example, CN106997972a and CN107275707a describe a method that recovers the positive electrode material using an acidic stripping method, but the acidic stripping method has a high requirement on equipment, and the positive electrode active material is greatly lost due to the reaction during the stripping process. JP5464137B2 describes a method for separating a current collector and an active material of a lithium battery and the use thereof, using a surfactant to separate a positive active material from a positive current collector. In the prior art, sulfuric acid and hydrochloric acid are mostly adopted as stripping agents, and when the acid stripping agents are used for stripping the positive electrode material, the positive electrode active material is promoted to generate larger loss due to reaction in the stripping process, and the recovery rate of the positive electrode material is lower.
In the prior art, the inorganic salt is peeled off by a polar solvent, the binder is peeled off by an organic solvent, and the positive electrode is peeled off by an alkali. The positive and negative electrode materials are stripped in a grading manner, and the positive and negative electrode materials are stripped at the same time. But the method for recovering the positive electrode active material, the negative electrode material and the complete copper-aluminum foil respectively and simultaneously recovering the electrolyte is almost absent.
Therefore, it is necessary to provide a new stripping agent and stripping process for waste lithium battery electrode materials, so as to solve the technical problems of the prior stripping technology that the positive and negative electrodes need to be separated, or the problems of complex process, or large environmental pollution, or low material recovery rate and purity, or the problem that electrolyte cannot be effectively recovered, and the like.
Disclosure of Invention
The invention mainly aims to provide a stripping agent and a stripping method of waste lithium ion battery electrode materials, which are used for solving the problems that the prior stripping technology has the technical problem that positive and negative electrodes are required to be separated, or the technology is complex, or the environmental pollution is large, or the material recovery rate and purity are low, or electrolyte cannot be effectively recovered, and the like.
In order to achieve the above object, according to one aspect of the present invention, there is provided a stripping agent comprising an organic acid, an acid salt of phosphoric acid, and a corrosion inhibitor, wherein the organic acid is selected from one or more of oxalic acid, succinic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, citric acid, maleic acid, and fumaric acid; the acid salt of phosphoric acid is selected from one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate and potassium dihydrogen phosphate; the corrosion inhibitor is one or more selected from sodium salt, potassium salt, ammonium salt, mercaptan, thiourea, boric acid and nicotinic acid; and/or the pH of the solution of the stripping agent after being dissolved in water is 0.1-5.
Further, the sodium salt is one or more selected from the group consisting of sodium benzenesulfonate, sodium dodecylbenzenesulfonate, sodium thiosulfate, sodium oxalate, sodium dodecylsulfate, sodium gluconate, sodium chloride, disodium edetate and tetrasodium edetate; preferably, the potassium salt is selected from one or more of potassium chloride, potassium phosphate and potassium permanganate, more preferably potassium chloride and/or potassium permanganate; preferably, the ammonium salt is selected from one or more of ammonium oxalate, tetrabutylammonium sulfate and ammonium chromate, more preferably ammonium oxalate and/or ammonium chromate.
Further, the mass ratio of the organic acid to the acid salt of the phosphoric acid to the corrosion inhibitor is (0.5-25): 1 (0.01-15); preferably, the organic acid comprises oxalic acid, the acid salt of phosphoric acid comprises monopotassium phosphate, and when the corrosion inhibitor comprises sodium dodecyl benzene sulfonate, the mass ratio of the organic acid to the acid salt of phosphoric acid to the corrosion inhibitor is (0.5-3): 1 (0.01-0.15); or when the organic acid comprises dodecylbenzene sulfonic acid and maleic acid, the acid salt of phosphoric acid comprises monopotassium phosphate, and the corrosion inhibitor comprises sodium thiosulfate, sodium oxalate and mercaptan, the mass ratio of the organic acid to the acid salt of phosphoric acid to the corrosion inhibitor is (10-25): 1 (1-15); or when the organic acid comprises succinic acid and benzenesulfonic acid, the acid salt of phosphoric acid comprises monopotassium phosphate, and the corrosion inhibitor comprises sodium benzenesulfonate, sodium dodecyl sulfate and ammonium oxalate, the mass ratio of the organic acid to the acid salt of phosphoric acid to the corrosion inhibitor is (10-25): 1 (1-15); alternatively, the organic acid contains oxalic acid, the acid salt of phosphoric acid contains monopotassium phosphate, and when the corrosion inhibitor contains sodium benzenesulfonate, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (0.5-3): 1 (0.1-1.5).
In order to achieve the above object, according to one aspect of the present invention, there is provided a stripping liquid comprising: the pH of the stripping agent and water is 0.1-5.
Further, the pH of the stripping liquid is 0.5 to 2, more preferably 0.5 to 1; preferably, the stripping liquid has a mass concentration of the organic acid of 0.2 to 6%, more preferably 2 to 4%, and/or an acid salt of phosphoric acid of 0.05 to 6%, more preferably 0.2 to 3%, and/or a corrosion inhibitor of 0.01 to 10%, more preferably 0.05 to 5%.
According to another aspect of the present invention, there is provided a stripper composition comprising a primary stripper and a secondary stripper; wherein the primary stripping agent comprises a weakly basic compound; the secondary stripping agent is the stripping agent.
Further, the weakly basic compound is selected from one or more of the group consisting of urea, ammonium carbonate, ammonium oxalate, sodium carbonate, sodium bicarbonate, potassium carbonate, ammonium bicarbonate, sodium phosphate, disodium hydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, ammonium hydrogen phosphate, sodium formate, sodium acetate, sodium acrylate, sodium citrate, sodium malate, sodium silicate, and sodium metasilicate; preferably, the primary stripper further comprises a neutral inorganic salt; preferably the neutral inorganic salt is selected from one or more of sodium chloride, potassium chloride, sodium sulphate, magnesium sulphate and potassium sulphate.
Further, the mass ratio of the weakly basic compound to the neutral inorganic salt is (1-20): 1; preferably, the primary stripping agent comprises a weakly basic compound comprising sodium carbonate, potassium phosphate, potassium bicarbonate and urea; the mass ratio of the sodium carbonate to the potassium phosphate to the potassium bicarbonate to the urea is (5-15): 1-10): 1-5): 0.5-2; further preferably, the primary stripping agent comprises a weakly basic compound and a neutral inorganic salt, the weakly basic compound comprises sodium carbonate, potassium phosphate, potassium bicarbonate and urea, the neutral inorganic salt comprises sodium sulfate and sodium chloride, and the mass ratio of the weakly basic compound to the neutral inorganic salt is (5-15): 1; alternatively, the primary stripping agent comprises a weakly basic compound comprising sodium bicarbonate, ammonium phosphate, and ammonium hydrogen phosphate; the mass ratio of sodium bicarbonate to ammonium phosphate to ammonium hydrogen phosphate is (5-15): 1-10): 1-5): 0.5-2; alternatively, the primary stripping agent comprises a weakly basic compound comprising sodium malate, sodium silicate, sodium metasilicate, and sodium carbonate; the mass ratio of the sodium malate to the sodium silicate to the sodium carbonate is (5-15): 1-10): 1-5): 0.5-2; alternatively, the primary stripping agent comprises a weakly basic compound and a neutral inorganic salt, the weakly basic compound comprises sodium bicarbonate and potassium phosphate, the neutral inorganic salt comprises potassium sulfate and sodium chloride, and the mass ratio of the weakly basic compound to the neutral inorganic salt is (1-10): 1.
According to another aspect of the present invention, there is provided a combined stripping solution comprising: the first-stage stripping liquid comprises the first-stage stripping agent and water; the secondary stripping liquid comprises the secondary stripping agent and water, or the stripping liquid.
Further, the pH of the primary stripping solution is 8 to 13, preferably 10 to 11.5; preferably, the mass concentration of the weakly basic compound is 0.5 to 15%, more preferably 0.5 to 2%.
According to another aspect of the present invention, there is provided a peeling method of an electrode material of a waste lithium ion battery, the peeling method comprising: pretreating a waste lithium ion battery to obtain a first mixed material containing a positive plate, a negative plate and a diaphragm, wherein the positive plate comprises a positive electrode material and an aluminum foil, and the negative plate comprises a negative electrode material and a copper foil; and carrying out grading stripping treatment on the positive plate and the negative plate by using stripping liquid to obtain a positive electrode material, a negative electrode material, copper foil and aluminum foil, wherein the stripping liquid comprises the combined stripping liquid.
Further, the combined stripping liquid comprises a primary stripping liquid and a secondary stripping liquid; the hierarchical stripping process includes: carrying out primary stripping treatment on the first mixed material by adopting a primary stripping solution to obtain a negative electrode material and a primary stripping product containing a positive electrode plate, a diaphragm and a copper foil; performing secondary stripping treatment on the primary stripping product by adopting a secondary stripping solution to obtain a positive electrode material, copper aluminum foil and a diaphragm; preferably, the time of the primary stripping treatment is 0.5 to 20 minutes; the second-stage stripping treatment time is 0.5-20 min.
Further, the preprocessing step comprises: and sequentially carrying out discharge treatment, disassembly and cutting treatment on the waste lithium ion batteries to obtain a first mixed material.
Further, the stripping agent, the stripping liquid, the stripping agent composition or the combined stripping liquid are applied to the field of stripping of waste lithium ion batteries.
The technical staff creatively select the acid salt of the organic acid with the phosphoric acid and the corrosion inhibitor as components of the stripping agent, and can only act on the surfaces of the anode material and the aluminum foil when the stripping agent is used for stripping the waste lithium ion battery electrode material, but can not react with the material, so that the recovery rate and purity of the severely corroded material and the anode material are reduced. Therefore, the positive electrode material of the lithium battery can be quickly and completely stripped from the positive electrode plate, and the corrosion and dissolution of the positive electrode material are effectively inhibited, so that the positive electrode material is promoted to have higher recovery rate. Meanwhile, the remaining integrity of other component materials (membrane, copper foil and aluminum foil) is better, and further, the copper foil and aluminum foil with higher integrity can be recycled in the subsequent process, so that a better condition is created for recycling valuable metals, and the probability of metal impurities entering the recycled anode and cathode materials is reduced, so that the anode and cathode materials with higher purity are obtained. In addition, the whole stripping recovery process is simple to operate, less in three wastes, more environment-friendly and pollution-free in process, low in cost and easy to obtain components, and lower in cost.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present invention will be described in detail with reference to examples.
In this context, the values are by weight unless otherwise specified.
Herein, the positive electrode material includes a positive electrode active material, a binder, and a conductive agent. The anode material includes an anode active material and a binder.
As described in the background section, the prior stripping technology has the technical problems of the separation of the positive electrode and the negative electrode, or the problems of complex process, large environmental pollution, low material recovery rate and purity, and the like. In order to solve the problem, the invention provides a stripping agent, which comprises organic acid, acid salt of phosphoric acid and corrosion inhibitor, wherein the organic acid is one or more of oxalic acid, succinic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, citric acid, maleic acid or fumaric acid; the acid salt of phosphoric acid is one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate or potassium dihydrogen phosphate; the corrosion inhibitor is one or more selected from sodium salt, potassium salt, ammonium salt, mercaptan, thiourea, boric acid or nicotinic acid; and/or the pH of the solution of the stripping agent after being dissolved in water is 0.1-5.
The technical staff creatively select the acid salt of the organic acid matched with the phosphoric acid and the corrosion inhibitor as components of the stripping agent, and can only act on the surfaces of the positive electrode material and the aluminum foil when the stripping agent is used for stripping the waste lithium ion battery electrode material, but can not obviously react with the material, so that the material is severely corroded. Therefore, the positive electrode material of the lithium battery can be quickly and completely stripped from the positive electrode plate, and the corrosion and dissolution of the positive electrode material are effectively inhibited, so that the positive electrode material is promoted to have higher recovery rate. Meanwhile, the remaining integrity of other component materials (membrane, copper foil and aluminum foil) is better, and further, the copper foil and aluminum foil with higher integrity can be recycled in the subsequent process, so that a better condition is created for recycling valuable metals, and the probability of metal impurities entering the recycled anode and cathode materials is reduced, so that the anode and cathode materials with higher purity are obtained. In addition, the whole stripping recovery process is simple to operate, less in three wastes, more environment-friendly and pollution-free in process, low in cost and easy to obtain components, and lower in cost.
In a word, when the stripping agent is subsequently applied to a battery stripping process, the stripping accuracy is higher, the reaction is milder, the stripping effect is better, and the raw material cost is lower. When the stripping agent is applied to the stripping technology, the positive electrode material, the negative electrode material, the copper foil and the aluminum foil can be effectively separated under the controllable condition, and each component has high recovery rate, especially the positive electrode material and the negative electrode material.
In order to improve the synergistic effect of the corrosion inhibitor and the acid salts of the organic acid and the phosphoric acid, thereby further inhibiting the corrosion of the acid compound on the positive electrode material, further improving the safety of the recovery treatment of the waste lithium ion battery and the recovery rate of the positive electrode material, in a preferred embodiment, when the corrosion inhibitor is selected to be used in combination with the acid salts of the organic acid and the phosphoric acid, the sodium salt is preferably selected from one or more of sodium benzenesulfonate, sodium dodecylbenzenesulfonate, sodium thiosulfate, sodium oxalate, sodium dodecylsulfate, sodium gluconate, sodium chloride, disodium ethylenediamine tetraacetate and tetrasodium ethylenediamine tetraacetate. More preferably, the potassium salt is selected from potassium chloride and/or potassium permanganate; the ammonium salt is selected from ammonium oxalate and/or ammonium chromate.
In a preferred embodiment, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (0.5-25): 1 (0.01-15). In some alternative embodiments, the mass ratio of organic acid, acid salt of phosphoric acid, and corrosion inhibitor is 1.5:1:0.05, 0.75:1:1.67, 0.75:1:0.25, 16:1:8, 7.5:1:4, 1.17:1:0.67.
In order to further improve the recovery rate and recovery purity of the positive electrode material, in a more preferred embodiment, the organic acid contains oxalic acid, the acid salt of phosphoric acid contains monopotassium phosphate, and the corrosion inhibitor contains sodium dodecylbenzenesulfonate, the mass ratio of the organic acid, the acid salt of phosphoric acid, and the corrosion inhibitor is (0.5 to 3): 1 (0.01 to 0.15), more preferably (1 to 2): 1 (0.01 to 0.1), for example, 1.5:1:0.05.
Alternatively, preferably, the organic acid comprises dodecylbenzenesulfonic acid and maleic acid, the acid salt of phosphoric acid comprises monopotassium phosphate, and the corrosion inhibitor comprises sodium thiosulfate, sodium oxalate and mercaptan, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (10-25): 1 (1-15), more preferably (10-20): 1 (5-10), for example 16:1:8. It is further preferable that the mass ratio of dodecylbenzenesulfonic acid to maleic acid in the organic acid is (0.5 to 10): (0.01 to 1), for example, 3:0.2. It is further preferred that the mass ratio of sodium thiosulfate, sodium oxalate and mercaptan in the corrosion inhibitor is (0.5-5): (0.01-1.5): (0.01-1), e.g. 1:0.4:0.2.
Alternatively, preferably, the organic acid comprises succinic acid and benzenesulfonic acid, the acid salt of phosphoric acid comprises monopotassium phosphate, and the corrosion inhibitor comprises sodium benzenesulfonate, sodium dodecylsulfate and ammonium oxalate, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (10-25): 1 (1-15), more preferably (10-20): 1 (5-10), for example 16:1:8. It is further preferable that the mass ratio of succinic acid to benzenesulfonic acid in the organic acid is (0.5-10): (0.01-1), for example, 3:0.2. It is further preferred that the mass ratio of sodium benzenesulfonate, sodium dodecylsulfate and ammonium oxalate in the corrosion inhibitor is (0.5-5): (0.01-1.5): (0.01-1), for example 1:0.4:0.2.
Alternatively, preferably, the organic acid comprises oxalic acid, the acid salt of phosphoric acid comprises monopotassium phosphate, and the corrosion inhibitor comprises sodium benzenesulfonate, the mass ratio of the organic acid, the acid salt of phosphoric acid, and the corrosion inhibitor is (0.5-3): 1 (0.1-1.5), more preferably (1-1.5): 1 (0.5-1), for example, 1.17:1:0.67.
The invention also provides a stripping liquid, which comprises the following components: the stripping agent and water according to the present invention have a pH of 0.1 to 5, for example, 0.56, 0.65, 0.69, 0.72, 0.73, 1.19, 1.22, 1.23, 1.27, 1.28, 1.31, 1.68.
The technical staff creatively select the acid salt of the organic acid matched with the phosphoric acid and the corrosion inhibitor as components of the stripping agent, and can only act on the surfaces of the positive electrode material and the aluminum foil when the stripping agent is used for stripping the waste lithium ion battery electrode material, but can not obviously react with the material, so that the material is severely corroded. Therefore, the positive electrode material of the lithium battery can be quickly and completely stripped from the positive electrode plate, and the corrosion and dissolution of the positive electrode material are effectively inhibited, so that the positive electrode material is promoted to have higher recovery rate. Meanwhile, the remaining integrity of other component materials (membrane, copper foil and aluminum foil) is better, and further, the copper foil and aluminum foil with higher integrity can be recycled in the subsequent process, so that a better condition is created for recycling valuable metals, and the probability of metal impurities entering the recycled anode and cathode materials is reduced, so that the anode and cathode materials with higher purity are obtained. In addition, the whole stripping recovery process is simple to operate, less in three wastes, more environment-friendly and pollution-free in process, low in cost and easy to obtain components, and lower in cost.
In a word, when the stripping agent is subsequently applied to a battery stripping process, the stripping accuracy is higher, the reaction is milder, the stripping effect is better, and the raw material cost is lower. When the stripping agent is applied to the stripping technology, the positive electrode material, the negative electrode material, the copper foil and the aluminum foil can be effectively separated under the controllable condition, and each component has high recovery rate, especially the positive electrode material and the negative electrode material.
The pH of the stripping liquid is preferably 0.5 to 2, more preferably 0.5 to 1. In order to further improve the stripping effect of the stripping liquid on the cathode material, the mass concentration of the organic acid, the acid salt of phosphoric acid and the slow release agent can be further optimized. In a preferred embodiment, the concentration of the organic acid in the stripping solution is 0.2 to 6% by mass, such as 0.3%, 1.5%, 3%, 3.2%, 3.5%, 4.5%, more preferably 2 to 4%. In a preferred embodiment, the mass concentration of the acid salt of phosphoric acid in the stripping solution is 0.05 to 6%, such as 0.2%, 0.4%, 2%, 3%, 6%, more preferably 0.2 to 3%. In a preferred embodiment, the mass concentration of the corrosion inhibitor in the stripping solution is 0.01 to 10%, such as 0.01%, 0.1%, 0.5%, 1.6%, 2%, 10%, more preferably 0.05 to 5%, in order to further enhance the synergistic effect of the corrosion inhibitor. Based on the above, in the recycling application of the waste lithium ion battery, the stripping liquid can further corrode the surfaces of the aluminum foil and the positive electrode material, so that the positive electrode material is stripped from the aluminum foil. Meanwhile, the stripping liquid can act on the surfaces of the positive electrode material and the aluminum foil more intensively, so that the aluminum foil and the positive electrode material are prevented from being corroded severely, and the integrity of the aluminum foil and the positive electrode material is damaged.
The invention also provides a stripping agent composition, which comprises a primary stripping agent and a secondary stripping agent; wherein the primary stripping agent comprises a weakly basic compound; the secondary stripping agent is the stripping agent disclosed by the invention.
The stripper composition of the present invention comprises a primary stripper (comprising a weakly basic compound) and a secondary stripper. First, when the primary stripping agent of the present invention is used for stripping the electrode material of the waste lithium ion battery, on one hand, it can absorb and fix the electrolyte (including electrolyte and electrolyte solvent and its hydrolysis products) in the battery. On the other hand, the primary stripping agent can also provide a weak alkaline environment, under the environment, the stripping agent can quickly strip and drop the negative electrode material of the lithium battery from the negative electrode plate, and the positive electrode plate is not stripped and can keep a relatively complete state.
Specifically, the primary stripping agent and the secondary stripping agent in the stripping agent composition of the invention are independent, and can be used singly or in combination when in application. In a preferred embodiment, the primary stripping agent and the secondary stripping agent are used in combination, the primary stripping agent solution is used for stripping the negative electrode material, the secondary stripping agent solution is used for stripping the positive electrode material, and the positive electrode material and the negative electrode material are separated in a grading manner, so that effective collection is realized.
In a preferred embodiment, the weakly basic compound is selected from one or more of urea, ammonium carbonate, ammonium oxalate, sodium carbonate, sodium bicarbonate, potassium carbonate, ammonium bicarbonate, sodium phosphate, disodium hydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, ammonium hydrogen phosphate, sodium formate, sodium acetate, sodium acrylate, sodium citrate, sodium malate, sodium silicate, and sodium sulfite. The alkalescent compound is selected from the types, on one hand, the alkaline environment provided by the alkalescent compound is more suitable for stripping of the anode material, the anode material with higher quality and higher recovery rate can be obtained under the condition of not damaging other components, and meanwhile, the alkalescent compound can be prevented from reacting with the cathode material as much as possible, so that the problem of doping of the cathode material during stripping of the anode material is effectively avoided, and further, the two-stage stripping agent is promoted to have higher yield and purity when being cooperatively matched for use. On the other hand, the electrolyte can be absorbed and fixed more effectively, so that the subsequent recovery of the electrolyte is facilitated.
In a preferred embodiment, the primary stripping agent further comprises a neutral inorganic salt selected from one or more of sodium chloride, potassium chloride, sodium sulfate, magnesium sulfate, and potassium sulfate. Based on the above, when the stripping agent is dissolved in water to form the stripping liquid, the stability of the stripping agent solution is further improved, the reduction speed of the stripping effect is slowed down, and meanwhile, the processing capacity of the stripping agent per unit mass can be further improved. More preferably, the mass ratio of the weakly basic compound to the neutral inorganic salt is (1 to 20): 1.
In order to further enhance the stripping effect of the primary stripping agent and thereby enhance the yield of each component material in the battery stripping process, in a preferred embodiment, the primary stripping agent comprises a weakly basic compound selected from the group consisting of sodium carbonate, potassium phosphate, potassium bicarbonate and urea; the mass ratio of the sodium carbonate to the potassium phosphate to the potassium bicarbonate to the urea is (5-15): 1-10): 1-5): 0.5-2, more preferably (5-10): 2-8): 1-3): 0.5-1.5, for example 8:5:2:1. It is further preferred that the primary stripping agent comprises a weakly basic compound selected from sodium carbonate, potassium phosphate, potassium bicarbonate and urea and a neutral inorganic salt selected from sodium sulfate and sodium chloride, the mass ratio of weakly basic compound to neutral inorganic salt being (5-15): 1, e.g. 8:1. It is further preferable that the mass ratio of sodium sulfate to sodium chloride in the neutral inorganic salt is (0.5 to 2): (0.1 to 5), for example, 1:1.
Alternatively, preferably, the primary stripping agent comprises a weakly basic compound selected from the group consisting of sodium bicarbonate, ammonium phosphate and ammonium hydrogen phosphate; the mass ratio of the sodium bicarbonate to the ammonium phosphate is (5-15): 1-10): 1-5): 0.5-2, more preferably (5-10): 2-8): 1-3): 0.5-1.5, for example 8:5:2:1.
Alternatively, preferably, the primary stripping agent comprises a weakly basic compound selected from sodium malate, sodium silicate, sodium metasilicate, and sodium carbonate; the mass ratio of the sodium malate to the sodium silicate to the sodium carbonate is (5-15): (1-10): (1-5): (0.5-2), more preferably (5-10): (2-8): (1-3): (0.5-1.5), for example 8:5:2:1.
Alternatively, preferably, the primary stripping agent comprises a weakly basic compound selected from sodium bicarbonate and potassium phosphate and a neutral inorganic salt selected from potassium sulfate and sodium chloride, the mass ratio of weakly basic compound to neutral inorganic salt being (1 to 10): 1, more preferably (1 to 5): 1, for example 4.3:1. It is further preferred that the mass ratio of sodium bicarbonate to potassium phosphate in the weakly basic compound is (1 to 15): (1 to 10), for example 8:5. It is further preferred that the mass ratio of potassium sulfate to sodium chloride in the neutral inorganic salt is (1 to 5): (0.5 to 5), for example, 2:1.
The invention also provides a combined stripping solution, which comprises a primary stripping solution and a secondary stripping solution. Wherein the primary stripping liquid comprises the primary stripping agent and water; the secondary stripping liquid comprises the stripping agent and water, or the stripping liquid.
Based on the foregoing, the primary stripping agent of the present invention is dissolved in water to form a primary stripping solution. And then the electrolyte (comprising electrolyte, electrolyte solvent and hydrolysis products thereof) in the fixed battery can be absorbed, so that the electrolyte can be effectively recycled. Meanwhile, the primary stripping liquid can also provide a weak alkaline environment, under the environment, the stripping liquid can quickly strip and drop the negative electrode material of the lithium battery from the negative electrode plate, and the positive electrode plate is not stripped and can keep a relatively complete state.
And secondly, the stripping agent disclosed by the invention is dissolved in water to form a secondary stripping solution, and when the stripping agent is used for stripping the electrode material of the waste lithium ion battery, the stripping agent can only act on the surfaces of the positive electrode material and the aluminum foil and can not react with the material, so that the material is severely corroded. Therefore, the synergistic corrosion inhibitor can achieve the beneficial effects of quickly and completely stripping and falling off the positive electrode material of the lithium battery from the positive electrode plate, and the corrosion dissolution of the positive electrode material is effectively inhibited, so that the positive electrode material is promoted to have higher recovery rate. Meanwhile, the remaining integrity of other component materials (membrane, copper foil and aluminum foil) is better, and further, the copper foil and aluminum foil with higher integrity can be recycled in the subsequent process, so that a better condition is created for recycling valuable metals, and the probability of metal impurities entering the recycled anode and cathode materials is reduced, so that the anode and cathode materials with higher purity are obtained. In addition, the whole stripping recovery process is simple to operate, less in three wastes, more environment-friendly and pollution-free in process, low in cost and easy to obtain components, and lower in cost.
In a word, when the stripping agent is subsequently applied to a battery stripping process, the stripping accuracy is higher, the reaction is milder, the stripping effect is better, and the raw material cost is lower. When the stripping agent is applied to the stripping technology, the positive electrode material, the negative electrode material, the copper foil and the aluminum foil can be effectively separated under the controllable condition, and each component has high recovery rate, especially the positive electrode material and the negative electrode material.
In order to further enhance the stripping effect of the primary stripping solution, in a preferred embodiment, the pH of the primary stripping solution is 8 to 13, optionally 8.10, 10.31, 11.13, 11.17, 11.20, 11.25, 11.28, 11.75, 11.88, 12.21; preferably 10 to 11.5.
In a preferred embodiment, the mass concentration of the weakly basic compound in the primary stripping solution is 0.5 to 15%, for example 0.5wt%, 1.3wt%, 1.6wt%, 2.4wt%, 7wt%, more preferably 0.5 to 2%. Based on this, the alkaline environment provided by the method is more suitable for stripping the negative electrode material, and the negative electrode material with high quality and high recovery rate can be obtained without damaging other components. In particular, the electrolyte can be absorbed and fixed more effectively, and the subsequent recovery of the electrolyte is facilitated.
The invention also provides a stripping method of the electrode material of the waste lithium ion battery, which comprises the steps of preprocessing the waste lithium ion battery to obtain a first mixed material containing a positive plate, a negative plate and a diaphragm, wherein the positive plate comprises a positive electrode material and an aluminum foil, and the negative plate comprises a negative electrode material and a copper foil; and carrying out grading stripping treatment on the positive plate and the negative plate by using stripping liquid to obtain a positive electrode material, a negative electrode material, copper foil and aluminum foil, wherein the stripping liquid comprises the combined stripping liquid.
Based on the foregoing, the invention can obtain the anode material and the cathode material with high recovery rate and purity and the copper foil aluminum foil with high integrity without crushing and sorting. Meanwhile, the stripping agent can effectively fix the electrolyte, and has the advantages of low cost, easy obtainment of components, no pollution, simple stripping process operation and no environmental pollution.
Preferably, the combined stripping solution comprises a primary stripping solution and a secondary stripping solution; the hierarchical stripping process includes: carrying out primary stripping treatment on the first mixed material by adopting a primary stripping solution to obtain a negative electrode material and a primary stripping product containing a positive electrode plate, a diaphragm and a copper foil; and (3) carrying out secondary stripping treatment on the primary stripping product by adopting a secondary stripping solution to obtain the anode material, the aluminum foil and the diaphragm. Based on the operation, the anode and cathode materials are precisely stripped in a grading way, the reaction is mild, the stripping effect is better, and the raw material cost is lower. Meanwhile, in the process of realizing accurate stripping of the electrode material by using the stripping agent, the electrolyte is recycled in a harmless way, so that the electrode material stripping agent is more environment-friendly. In addition, based on the stripping agent, the integrity of the copper-aluminum foil can be guaranteed to the greatest extent, the recovery rate of the copper-aluminum foil is improved, metal impurities are prevented from entering the recovered anode and cathode materials, the purity of the obtained anode materials is higher, a better condition is created for the subsequent recovery and reutilization of valuable metals, the three wastes in the whole recovery process are fewer, the cost is lower, and the process is more environment-friendly.
In order to make the peeling effect of the primary peeling treatment and the secondary peeling treatment better, it is preferable that the time of the primary peeling treatment is 0.5 to 20 minutes; the second-stage stripping treatment time is 0.5-20 min. Optionally, the first-stage stripping treatment is performed for 0.5min, 0.7min, 1min, 3min, 5min, etc.; the secondary stripping treatment time is 2.5min, 3min, 4min, 6min, 7min, 8min, 9min, etc.
In an alternative embodiment, the reaction mixture is screened through a screen while the primary stripping treatment is performed, so as to obtain undersize materials, namely a negative electrode material and a primary stripping solution, and oversize materials are primary stripping products containing a positive electrode plate, a diaphragm and a copper foil. And then, draining the primary stripping product containing the positive electrode plate, the diaphragm and the copper foil, and then carrying out secondary stripping treatment. And (3) carrying out secondary stripping treatment, and screening the reaction mixture to obtain a screen material which is a positive electrode material and a secondary stripping liquid, wherein the screen material is a secondary stripping product containing copper aluminum foil and a diaphragm. And then respectively carrying out filter pressing separation on the undersize products to respectively obtain a negative electrode material and a primary stripping liquid, and a positive electrode material and a secondary stripping liquid.
Preferably, the pretreatment step comprises the steps of sequentially carrying out discharge treatment, disassembly and cutting treatment on the waste lithium ion batteries to obtain a first mixed material. Although retired spent lithium ion batteries have reached the end of their useful life, a portion of the residual power is typically retained. In order to avoid the spontaneous ignition and the intense heat release caused by the ignition in the disassembly and cutting process, and simultaneously to avoid the low recovery rate of lithium caused by more metal lithium at the negative electrode, and to avoid the intense reaction heat release after the contact of the cell fragments and the stripping liquid, the waste lithium ion battery is firstly subjected to discharge treatment and disassembly and cutting pretreatment, so that the subsequent stripping and recovery treatment is facilitated.
Preferably, after the secondary stripping treatment, the stripping treatment further comprises the steps of sequentially carrying out winnowing treatment and color separation treatment on the secondary stripping product to obtain a diaphragm, a copper foil and an aluminum foil. The separator with the lightest density is separated from the mixture containing the separator and the copper aluminum foil under the action of air flow by utilizing the difference of the densities of the separator and the copper aluminum foil. More preferably, the secondary stripping product containing copper aluminum foil and the diaphragm is washed with clean water, drained and dried before the air separation, and then the air separation is carried out to separate the diaphragm. In an alternative embodiment, the copper foil and aluminum foil may be separated by color selection, and the resulting copper foil and aluminum foil may be packaged and sold directly.
In an alternative embodiment, after the fixed electrolyte is absorbed in the primary stripping solution to reach a certain concentration, the organic components and electrolyte salts in the electrolyte can be recovered by subsequent evaporation, and the evaporated water is reused to prepare a new stripping agent solution or used as washing water, so that the electrolyte is also more effectively recycled. Preferably, the electrolyte is recovered by concentration evaporation when the concentration of the electrolyte in the stripper solution is about 10 to 30%.
The retired lithium battery positive electrode material is a ferric lithium phosphate and/or a lithium manganate and/or a lithium cobaltate and/or a binary and/or ternary positive electrode material commonly used in the field. In a preferred embodiment, the method for recycling the lithium battery can be applied to aluminum shell batteries, soft package batteries, cylindrical batteries, battery waste pole pieces and pole piece scraps, and is applicable to waste lithium batteries with positive electrode material systems of any one or two or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide ternary, lithium nickel cobalt aluminate ternary, lithium manganese oxide or lithium nickel manganese oxide. The stripping method can treat not only the retired waste lithium batteries, but also waste pole pieces, pole piece leftover materials, unqualified batteries and the like of battery factories.
The invention also provides an application of the stripping agent, the stripping liquid, the stripping agent composition and the combined stripping liquid in the field of stripping of waste lithium ion batteries.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
The formulation of the stripping liquid composition in the examples and comparative examples of the present invention is shown in the following table 1 (pH is measured at room temperature):
TABLE 1
The stripping method comprises the following steps: and carrying out electric quantity detection and discharge treatment on the retired waste lithium ion battery square shell battery, cutting and disassembling the shell of the waste battery subjected to the discharge treatment to obtain a shelled battery cell, and cutting the battery cell into battery cell fragments.
200g of the cell fragments are respectively put into 1000g of primary stripping liquid of each example and comparative example to be subjected to primary stripping treatment until the negative active material falls off, screening is performed through a screen, the undersize is the negative material and the primary stripping liquid, respectively taking oversize into 1000g of secondary stripping liquid of each example and comparative example to be soaked until the positive material falls off, screening is performed through the screen, the undersize is the positive material and the secondary stripping liquid, washing and draining the undersize with pure water, drying at 80 ℃ to obtain a mixture of copper foil, aluminum foil and diaphragm, and then sequentially performing winnowing and color separation to obtain the diaphragm, copper foil and aluminum foil. And respectively press-filtering the undersize after stripping of each stage to obtain a filter cake anode material and a filter cake cathode material, and washing to obtain a clean anode material and a clean cathode material.
The recovery rate testing method comprises the following steps:
positive electrode material recovery = mass of recovered positive electrode material/mass of positive electrode material in battery x 100%
The mass obtaining method of the positive electrode material in the battery comprises the following steps: and corroding the quantified positive plate of the battery by using a sodium hydroxide solution, filtering out a positive material after aluminum foil in the positive plate completely disappears, and washing, drying and weighing to obtain the quality of the positive material in the battery.
Negative electrode material recovery = mass of recovered negative electrode material x purity/mass of negative electrode material in battery x 100%
The mass obtaining method of the anode material in the battery comprises the following steps: the negative plate is usually taken alone, and is peeled off in a first-stage peeling liquid after metering.
The purity testing method comprises the following steps:
cathode material purity = sum of nickel cobalt manganese mass fraction in recovered cathode material/sum of nickel cobalt manganese mass fraction in cathode material of battery x 100%
The mass fraction of the nickel-cobalt-manganese valuable metal can be obtained through ICP-OES or ICP-MS detection.
Negative electrode material purity= (1-recovery of sum of mass fraction of nickel, cobalt and manganese in negative electrode material/sum of mass fraction of nickel, cobalt and manganese in positive electrode material of battery) ×100%
Characterization of the properties:
the stripping liquid composition in each embodiment of the invention is used for stripping waste lithium ion batteries, and the recovery rates and purities of the positive electrode material and the negative electrode material are shown in the following table 2 respectively:
TABLE 2
The recovery rate of the copper foil and the aluminum foil in the embodiment 1 reaches 96.5%, and the obtained copper foil and aluminum foil have flat surfaces and no holes.
From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
as is clear from comparative examples 1 to 21, the primary stripping liquid had a pH of 10 to 11.5, and the stripping effect was more excellent. The pH is below the lower limit and the stripping effect will generally be somewhat poorer, for example 10 (8.1). When the pH is higher than the upper limit, the positive electrode material is partially peeled off during primary peeling, for example, example 4 (11.81), example 5 (12.21) and example 19 (11.7), and the other examples have a primary peeling liquid pH within the above range, so that the effect of peeling the negative electrode material is more excellent.
Further comparing example 1 with example 2, it is known that the addition of inorganic salt to the primary stripping agent is beneficial to improving the electrolysis rate, enhancing the flushing effect of the primary stripping agent on the hetero atoms, facilitating the subsequent further stripping treatment, and further obtaining a positive electrode material with higher recovery rate and higher purity.
Further, as is clear from comparison of examples 1, 3 and 6 to 19, the primary stripping agent preferably has a weakly basic compound concentration of 0.5 to 2% by mass, and the weakly basic compound concentration is lower than the lower limit of the above concentration, and the stripping effect is generally poor, and the positive electrode material is caused to fall off at the time of primary stripping when the concentration is higher than the upper limit of the above concentration.
For example, when the concentration of the weakly basic concentration compound in example 5 (15 wt%), example 4 (7 wt%) and example 19 (2.4 wt%) is too high, the positive electrode material is partially peeled off at the same time as the negative electrode material is peeled off, and thus, a part of the positive electrode material is mixed into the negative electrode material obtained by the subsequent collection, and although the recovery rate of the negative electrode material is slightly improved, the improved part is substantially the mixed positive electrode material, and the purity thereof is low. Meanwhile, the anode material has a loss in primary stripping, and even if the effect of stripping the anode by the secondary stripping liquid is good, the recovery rate of the anode can be reduced. In example 1, example 3, and examples 6 to 18, the mass percentage of the weakly basic compound in the primary stripping liquid is limited to the preferred range of the present application, which has a better stripping effect of the negative electrode material.
Further comparing examples 1, 3, and 6 to 19, it is understood that, in the primary stripping agent, the primary stripping agent is composed of a weakly basic compound selected from sodium carbonate, potassium phosphate, potassium bicarbonate, and urea; the mass ratio of sodium carbonate, potassium phosphate, potassium bicarbonate and urea is (5-15): 1-10): 1-5): 0.5-2, for example 1; or the primary stripping agent is composed of a weakly basic compound selected from sodium bicarbonate, ammonium phosphate and ammonium hydrogen phosphate; the mass ratio of sodium bicarbonate, ammonium phosphate and ammonium hydrogen phosphate is (5-15): 1-10): 1-5): 0.5-2, for example, example 9; alternatively, the primary stripping agent is composed of a weakly basic compound selected from sodium malate, sodium silicate, sodium metasilicate, and sodium carbonate; the mass ratio of sodium malate, sodium silicate, sodium metasilicate and sodium carbonate is (5-15): (1-10): (1-5): (0.5-2), for example 11; alternatively, the primary stripping agent is composed of a weakly basic compound selected from sodium hydrogencarbonate and potassium phosphate and a neutral inorganic salt selected from potassium sulfate and sodium chloride, and the mass ratio of the weakly basic compound to the neutral inorganic salt is (1-10): 1, for example, example 12. The primary stripping agent has better stripping effect based on the combination.
In view of the loss of the positive electrode material in the primary stripping in example 5 (15 wt%), example 4 (7 wt%), and example 19 (2.4 wt%), the recovery rate of the positive electrode was low even if the effect of stripping the positive electrode with the secondary stripping solution was good. Thus, in further comparing the effects of the secondary stripping agent, examples 1 to 3, examples 6 to 18, and examples 20 to 21 were selected for comparison.
Comparing examples 1 to 3, examples 6 to 18, and examples 20 to 21, it is clear that the secondary stripping solution has a pH of 0.5 to 1, and the stripping effect is better. If the pH is lower than the lower limit, partial corrosion of the copper-aluminum foil and the positive electrode material is caused, and the yield and purity are not high, and if the pH is higher than the upper limit, the peeling effect is generally poor, for example, example 6 (1.68), example 8 (1.22), example 14 (1.27), example 15 (1.23), example 16 (1.19), example 17 (1.31), and example 18 (1.28). The peeling effects of examples 1 to 3, 9, 10 to 12 (0.72), 13 (0.56), 20 (0.73) and 21 (0.69) are more excellent.
Further comparing examples 1 to 3, 9, 10 to 12 (0.72), 13 (0.56), 20 (0.73) and 21 (0.69), it is understood that the stripping liquid has a mass concentration of the organic acid of 2 to 4%, and/or the acid salt of phosphoric acid of 0.2 to 3%, and/or the corrosion inhibitor of 0.05 to 5%. Based on this, the secondary peeling effect is better. Among them, example 7 (4.5 wt%, 6wt%, 10 wt%) was inferior in peeling effect. In particular, the low recovery purity of the positive electrode material of example 10 is due to the poor stripping effect of the primary stripping agent, and a portion of the negative electrode material is stripped off during the secondary stripping and mixed into the positive electrode material, resulting in a low recovery purity.
Further comparing examples 1 to 3, examples 6 to 18 and examples 20 to 21, it is understood that the organic acid is selected from oxalic acid, the acid salt of phosphoric acid is selected from potassium dihydrogen phosphate, and the corrosion inhibitor is selected from sodium dodecylbenzenesulfonate, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (0.5 to 3): 1 (0.01 to 0.15), for example, example 1. Alternatively, the organic acid is selected from dodecylbenzenesulfonic acid and maleic acid, the acid salt of phosphoric acid is selected from potassium dihydrogen phosphate, and the corrosion inhibitor is selected from sodium thiosulfate, sodium oxalate and mercaptan, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (10-25) 1 (1-15), for example, example 13. Alternatively, when the organic acid is selected from succinic acid and benzenesulfonic acid, the acid salt of phosphoric acid is selected from potassium dihydrogen phosphate, and the corrosion inhibitor is selected from sodium benzenesulfonate, sodium dodecylsulfate and ammonium oxalate, the mass ratio of the organic acid, the acid salt of phosphoric acid and the corrosion inhibitor is (10-25): 1 (1-15), for example, example 20. Alternatively, the organic acid is selected from oxalic acid, the acid salt of phosphoric acid is selected from potassium dihydrogen phosphate, and the corrosion inhibitor is selected from sodium benzenesulfonate, the mass ratio of the organic acid, the acid salt of phosphoric acid, and the corrosion inhibitor is (0.5-3): 1 (0.1-1.5), for example, example 21. The secondary stripping agent has better stripping effect based on the specific combination.
In comparative example 1, the first stripping conditions were the same as in example 1, sulfuric acid and sodium benzenesulfonate were used in the second stripping agent, the second stripping time was longer than in examples 1 and 2, and the recovery rate and purity of the positive electrode material in the second stripping were both inferior to those in examples 1 and 2. In comparative example 2, the first stripping conditions were the same as in example 1, hydrochloric acid and sodium benzenesulfonate were used as the second stripping agent, the second stripping time was longer than in examples 1 and 2, and the recovery rate and purity of the positive electrode material in the second stripping were both inferior to those in examples 1 and 2. In comparative example 3, the primary stripping conditions were the same as in example 1, the secondary stripper components were single benzenesulfonic acid and sodium benzenesulfonate, the secondary stripping time was long, and the recovery rate and purity of the stripped positive electrode material were both poor. In comparative example 4, the first stripping conditions were the same as in example 1, the second stripping agent component was citric acid and sodium benzenesulfonate, the second stripping time was long and the recovery rate and purity of the stripped positive electrode material were significantly deteriorated. The secondary stripper component is free of the acid salt of phosphoric acid. In comparative example 5, the first stripping conditions were the same as in example 1, and citric acid, oxalic acid, succinic acid and sodium thiosulfate were used as the second stripping agent components, and the second stripping time was long and the recovery rate and purity of the stripped positive electrode material were significantly deteriorated.
As is clear from the comparison between the comparative examples and the examples of the present invention, when a single acid is used as the secondary stripping agent, the stripping effect is generally poor, and when an organic acid is used together with at least one acid salt of phosphoric acid and at least one corrosion inhibitor, the recovery rate and purity of the positive electrode material obtained by the secondary stripping are much better.
The innovation point of the invention is based on the following points:
1. the positive electrode material is stripped by adopting the combination of the acid salt of the organic acid and the phosphoric acid and the corrosion inhibitor, the recovery rate of the recovered positive electrode material is high, the introduced impurities are few, the purity is good, and the resource recovery rate is high. Meanwhile, the corrosion to the aluminum foil of the current collector is small, and a relatively complete aluminum foil can be obtained.
2. The acid stripping agent solution is easy to treat after being used, when the stripping agent effect is reduced, the light organic matters of the electrolyte are properly concentrated and distilled out, the precipitated salts are removed by filtration, the residual acid solution water supplementing and stripping agent supplementing can be continuously recycled, and the electrolyte is effectively recovered and disposed, so that the electrolyte is more effectively recycled.
3. Compared with the stripping with sulfuric acid and hydrochloric acid, the stripping agent and the stripping process have mild conditions, can be operated at normal temperature and normal pressure, and have lower requirements on equipment.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (14)
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