Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for recovering a waste lithium battery cathode material, which has low energy consumption, low pollution and high utilization rate.
The invention relates to a method for recovering lithium in a waste lithium battery positive electrode material, which is characterized by comprising the following steps of: roasting waste lithium battery positive electrode material powder at 450-550 ℃ in an oxidizing atmosphere to obtain a pre-oxidized roasted product, leaching the pre-oxidized roasted product with an aqueous solution to obtain a first mixed solution and first sediments containing phosphorus, iron and carbon, adjusting the pH value of the first mixed solution to 6.5-7.5, performing first reaction and solid-liquid separation to obtain a second mixed solution containing lithium and second sediments enriched with Al and Cu, adjusting the pH value of the second mixed solution to 8.5-11, performing second reaction and solid-liquid separation to obtain a third mixed solution containing lithium and third sediments containing Ni, co and Mn.
According to the method for recovering the waste lithium battery anode material, the waste lithium battery anode material powder is subjected to pre-oxidation roasting, iron in the ferrous phosphate lithium battery black powder is fully oxidized and organic matters are completely removed by strictly controlling the sintering temperature within the range of the method in the pre-oxidation roasting process, the fluorine-containing organic solvent is included, and the oxidation of carbon is avoided, so that the influence of reducing atmosphere generated by carbon combustion on oxidizing atmosphere is avoided, the carbon is kept as much as possible, and the recovery rate of the carbon is increased. Meanwhile, the sufficient pre-oxidation of iron can reduce the leaching efficiency of Fe metal elements and the usage amount of an oxidant in the subsequent aqueous solution leaching process, and the first mixed solution obtained after leaching can complete the removal of impurity ions and the recovery of battery-grade lithium carbonate by accurately controlling the pH value.
In a preferred scheme, the waste lithium battery positive electrode material powder is a mixture of a waste lithium iron phosphate battery positive electrode material or at least one of negative electrode powder and a waste ternary lithium battery positive electrode material.
The inventor finds that in actual industry, a large amount of waste lithium battery positive electrode material powder is waste lithium iron phosphate battery positive electrode material, or a mixture of the waste lithium iron phosphate battery positive electrode material and at least one of negative electrode powder and waste ternary lithium battery positive electrode material. The reason is that in order to improve efficiency, the battery classification treatment is not carried out during the disassembly and crushing of the enterprises, but the mixed anode powder can be well recycled by adopting the technical scheme of the invention, and the resource utilization maximization is realized.
In actual operation, the step of providing a powdered material for a lithium iron phosphate battery comprises: performing complementary energy detection on a waste lithium ion battery, performing discharge treatment on the battery with higher residual electric energy, crushing and disassembling a battery shell to obtain a pole piece, and stripping a powder material from the pole piece to obtain the lithium iron phosphate powder material.
Preferably, the oxidizing atmosphere is selected from oxygen and/or air.
Preferably, the flow rate of the oxidizing atmosphere is 0.6 to 1L/min. The inventor finds that iron in the ferrous phosphate lithium battery black powder can be fully oxidized by introducing an oxidizing atmosphere, strictly controlling the roasting temperature to be 450-550 ℃, and controlling the flow of introducing the oxidizing atmosphere, organic matters including fluorine-containing organic solvents are removed, and oxidation of carbon is avoided, so that the influence of a reducing atmosphere generated by carbon combustion on the oxidizing atmosphere is avoided, the carbon is kept as much as possible, and meanwhile, when the pre-oxidized roasted product is subjected to acid leaching, leaching of iron is avoided under the condition of reducing the use of water dioxide, so that the content of impurity ions in the leaching solution is reduced.
In a preferable scheme, the roasting time is 1-1.5h.
In the preferred scheme, in the aqueous solution leaching process, the solid-liquid mass volume ratio of the pre-oxidized roasted product to the aqueous solution is 1g:5 to 8ml, preferably 1g:7 to 8ml.
Preferably, the aqueous solution is selected from deionized water, and the pH of the aqueous solution is adjusted to 2-5 by sulfuric acid or phosphoric acid.
In a preferable scheme, the temperature of the aqueous solution leaching is room temperature, and the leaching time is 1-1.5h.
In a preferable scheme, in the aqueous solution leaching process, an oxidant is added for assisting leaching, and the oxidant is H 2 O 2 Or O 2 。
Further preferably, the oxidizing agent is added in an amount to oxidize Fe in the pre-oxidized roast product 2+ 1.5-2.5, preferably 1.8-2.2 times the theoretical amount of (A).
The theoretical dosage of the hydrogen peroxide is calculated according to the molar ratio: m (H) 2 O 2 ):m(Fe 2+ )=0.5:1。
In the present invention, the residual Fe in the roasted product is pre-oxidized due to the oxidation 2+ The content is low, so the dosage of the hydrogen peroxide needed to be added is greatly reduced.
Preferably, at least one of calcium hydroxide, calcium oxide, magnesium oxide, sodium hydroxide and lithium hydroxide, preferably lithium hydroxide, is added to the first mixed solution, and the pH of the first mixed solution is adjusted to 6.5 to 7.5. LiOH is adopted to adjust pH, so that the introduction of impurity ions is avoided, liOH obtained by subsequent electrolysis can be adopted for circulation, and the loss of lithium can be avoided.
Preferably, the time of the first reaction is 20-40min after the pH value is kept stable.
In the actual operation process, the pH value can be stabilized after 10-20 min, and then the reaction is continued for 20-40min.
Preferably, the first sediment is cleaned, and the cleaned water washing liquid is added into the second mixed solution.
Preferably, at least one of calcium hydroxide, calcium oxide, magnesium oxide, sodium hydroxide and lithium hydroxide, preferably lithium hydroxide, is added to the second mixed solution, and the pH value of the first mixed solution is adjusted to 8.5-11. LiOH is adopted to adjust pH, so that the introduction of impurity ions is avoided, liOH obtained by subsequent electrolysis can be adopted for circulation, and the loss of lithium can be avoided.
Preferably, the time of the second reaction is 30-50min after the pH value is kept stable.
Preferably, the second sediments are cleaned, and the cleaned water washing liquid is added into the third mixed solution.
Preferably, the third mixed solution is subjected to diaphragm electrolysis to obtain sulfuric acid and lithium hydroxide.
Further preferably, the obtained sulfuric acid is returned to be used as a pH regulator in the leaching process of the aqueous solution of the pre-oxidation roasting product, so that the recycling of the sulfuric acid is realized.
In a preferred embodiment, the obtained lithium hydroxide solution is returned to the pH adjuster used in the first mixed solution or the second mixed solution.
Further preferably, heating the lithium hydroxide solution to 90-95 ℃, carbonizing, and performing solid-liquid separation to obtain lithium carbonate; the carbonization process is to introduce saturated solution of sodium carbonate or CO 2 。
Advantageous effects
Compared with the prior art, the method for recovering the metallic lithium from the waste lithium battery anode material in the industrialized mode is realized by simply obtaining the pre-oxidation roasting-leaching process, the ferrous iron in the powder is pre-oxidized into the ferric iron by pre-oxidation through controlling roasting temperature, time and other conditions in a pyrogenic process stage, organic matters are completely removed, the fluorine-containing organic solvent is included, and carbon oxidation is avoided as much as possible in the roasting process, so that the effects of avoiding generating reducing atmosphere and reducing carbon loss are achieved, the consumption of an oxidant and the residue of organic matters are reduced in the subsequent leaching and impurity removing processes, the pressure of the subsequent defluorination and organic matter removal is reduced, the recovery rate of lithium elements is improved, and resource waste is avoided.
Meanwhile, the lithium-containing leachate is subjected to sectional impurity removal, and the nickel, cobalt and manganese mixed salt with high purity can be obtained in the second section and can be further recovered. And is also beneficial to processing the battery waste mixed by the lithium iron phosphate and the ternary cathode material.
And moreover, the lithium sulfate solution is treated by adopting a diaphragm electrolysis method to generate lithium hydroxide and sulfuric acid, so that the generation of a large amount of sodium sulfate-containing wastewater in the traditional process is avoided, and the generated sulfuric acid can be used in the production process, so that the additional consumption of sulfuric acid is reduced, and the wastewater discharge and treatment cost is reduced.
Detailed Description
The following description will refer to the accompanying drawings to more fully describe the present disclosure. There is shown in the drawings exemplary embodiments of the present application. This application may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals designate identical or similar components.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, as used herein, "comprises" and/or "comprising" and/or "having," integers, steps, operations, components, and/or components, but does not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Furthermore, unless otherwise explicitly defined herein, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and this application and will not be interpreted in an idealized or overly formal sense.
Embodiments of the present application will now be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present application provides a method for recycling a positive electrode material of a lithium battery, including the following steps:
step S1: providing powdery waste lithium battery positive electrode material powder (which is a waste lithium iron phosphate battery positive electrode material, or a mixture of the waste lithium iron phosphate battery positive electrode material powder and negative electrode powder, or a mixture of the waste lithium iron phosphate battery positive electrode material powder and a waste ternary lithium battery positive electrode material.
In one embodiment, the step of providing the powder of the waste lithium battery positive electrode material includes: performing complementary energy detection on a waste lithium ion battery, performing discharge treatment on the battery with higher residual electric energy, crushing and disassembling a battery shell to obtain a pole piece, and stripping a powder material from the pole piece to obtain the lithium iron phosphate powder material.
Step S2: an oxidizing atmosphere is provided, and in the embodiment, mixed air (N2 79% and O2%) is adopted, a certain amount of powdery anode material is taken as a roasting raw material, and the roasting is carried out for 1 to 1.5 hours at the temperature of 450 to 550 ℃ to obtain a pre-oxidized roasting product.
In an embodiment, in the process of baking the oxidizing atmosphere and the cathode material to obtain the first baked product, a main oxidation reaction includes:
12LiFePO 4 +3O 2 =4Li 3 Fe 2 (PO 4 ) 3 +2Fe 2 O 3
C+O 2 =CO 2
C 3 H 4 O 3 /C 4 H 8 O 3 (l)→C 3 H 4 O 3 /C 4 H 8 O 3 (g) (volatilization)
nC 3 H 4 O 3 /C 4 H 8 O 3 (l)→nCH 3 OH(g)+nCO 2 (g) (decomposition)
(CH 2 CF 2 )n(s)+nO 2 (g)→nH 2 O(g)+nHF(g)+nCO 2 (g)
In one embodiment, the first baked product includes carbon dioxide, iron oxide, lithium iron phosphate, and gas generated by decomposition, volatilization, and combustion of an organic solvent.
And step S3: and acid leaching the first roasting product to obtain a first mixed solution enriched with lithium, aluminum, copper, nickel, cobalt and manganese and a first sediment enriched with iron phosphate and carbon.
In one embodiment, the first mixed solution is enriched in lithium sulfate and the first sludge is enriched in iron phosphate and carbon.
And (3) cooling the first roasting product obtained in the step (S2) to room temperature, heating, stirring and carrying out acid leaching to obtain a first mixed solution and first sediments, washing the first sediments again to obtain a water washing liquid and water washing dregs, adding the water washing liquid into the first mixed solution, and washing with water to reduce the loss of valuable metals possibly caused by carbon powder wrapping.
And step S4: adjusting the pH value of the first mixed solution to be 6.5-7.5, maintaining the pH value stable, reacting for 20-40 minutes, and performing solid-liquid separation to obtain a second mixed solution enriched with lithium and enriched Cu (OH) 2 And Al (OH) 3 The second sludge of (1).
In an implementationIn the examples, the second sludge was enriched with Cu (OH) 2 And Al (OH) 3 A mixture of (a).
Step S5: adding LiOH into the second mixed solution to adjust the pH value of the second mixed solution to be 8.5-11, maintaining the pH value stable, reacting for 30-50 minutes, and performing solid-liquid separation to obtain a third mixed solution enriched with lithium and Mn (OH) 2 、Ni(OH) 2 、Co(OH) 2 And a third sludge of MnO (OH).
In one embodiment, liOH is added to the second mixed solution to adjust the pH to a range of 8.5 to 11. LiOH is adopted to adjust pH, so that the introduction of impurity ions is avoided, liOH obtained by subsequent electrolysis can be adopted for circulation, and the loss of lithium can be avoided.
In one embodiment, the carbonate solution is a saturated solution of sodium carbonate or CO 2 And lithium carbonate is enriched in the fourth sediment.
The term "enriched" as used herein means that a mixed solution or sludge mainly contains a certain compound, or means that a compound of a certain element is mainly concentrated in a separated solution or in a separated sludge in a solid-liquid separation process. For example, in step S3, lithium, aluminum, copper, nickel, cobalt, manganese and their compounds are mainly separated into the first mixed solution, and the first sludge may contain lithium, aluminum, copper, nickel, cobalt, manganese and their compounds, but the amount of lithium, aluminum, copper, nickel, cobalt, manganese and their compounds in the first sludge is much less than that of lithium and manganese and their compounds in the first mixed solution; similarly, iron, carbon, phosphorus and their compounds are mainly separated into the first sludge, and the first mixed solution may contain iron, carbon, phosphorus and their compounds, but the amount of iron, carbon, phosphorus and their compounds in the first mixed solution is much less than that of the first sludge.
According to the method, the conditions such as roasting temperature, time and the like are controlled in a pyrogenic process stage through a pre-oxidation roasting-acid leaching process, ferrous iron in powder is oxidized into ferric iron in advance, organic matters are removed to the greatest extent, the organic matters comprise fluorine-containing organic solvents, and carbon oxidation is avoided as much as possible in the roasting process, so that the effects of avoiding generating reducing atmosphere and reducing carbon loss are achieved, the consumption of hydrogen peroxide reagents is reduced in subsequent acid leaching and impurity removal processes, the pressure of subsequent fluorine removal is reduced, the recovery rate of elements such as lithium, iron and carbon is improved, and resource waste is avoided.
The method for recovering the lithium battery cathode material has the advantages of simple process, high added value of products, cleanness, high efficiency and low energy consumption, accords with the development concept of green metallurgy, and can realize high-efficiency comprehensive utilization of valuable metals through the preoxidation roasting = acid leaching process.
Example 1
Step S1: preparing anode active powder: carrying out complementary energy detection on a waste lithium ion battery, carrying out discharge treatment on a battery with higher residual electric energy, crushing the battery shell to obtain a pole piece, and stripping a powder material from the pole piece so as to obtain waste lithium anode material powder (consisting of a lithium iron phosphate powder material and ternary lithium battery anode material powder), wherein the mass fractions of main metals of the obtained waste lithium anode material powder are as follows: 15.6% of Fe, 2.08% of Li, 39.3% of C, 0.25% of Ni, 0.17% of Co, 0.27% of Mn, 2.21% of Al and 1.69% of Cu.
Step S2: pre-oxidizing and roasting: an oxidizing atmosphere was provided, and mixed air (N) was used in this example 2 79%、O 2 21 percent) and taking a certain amount of powdery anode material as a roasting raw material, roasting for 1 hour at 500 ℃ to obtain a pre-oxidized roasting product, controlling the flow of mixed air to be 0.6L/min, and immediately taking out the pre-oxidized roasting product after heating.
And step S3: acid leaching lithium extraction: mixing the roasted product in the step S2 at a ratio of 1g: dissolving 8mL of solid-liquid ratio in 0.15mol/L dilute sulfuric acid solution, adding 1.4mL of hydrogen peroxide for reaction, stirring and reacting for 1h at 25 ℃, and performing solid-liquid separation by using a Buchner funnel after leaching. The filter residue is solid residue containing iron, carbon and phosphorus compounds and other impurities, and the filtrate is water solution mainly containing sulfate of lithium, aluminum, copper, nickel, cobalt and manganese. ICP content analysis shows that the leaching rate of lithium is 95 percent, and the leaching rate of iron is 2 percent.
And step S4: removing aluminum and copper: and (3) adjusting the pH value of the filtrate obtained in the step (S3) to 6 by using a pH regulator (lithium hydroxide), reacting for 20 minutes under stable pH, and filtering to obtain filter residue containing copper and aluminum and a lithium-rich solution.
Step S5: removing nickel, cobalt and manganese: and (3) adjusting the pH value of the filtrate obtained in the step (S4) to 9.5 by using a pH regulator (lithium hydroxide), reacting for 30 minutes under stable pH, and filtering to obtain filter residue containing nickel, cobalt and manganese and a lithium-rich solution.
Step S6: preparing a lithium hydroxide product: and (4) putting the lithium-rich solution obtained in the step (S5) into a diaphragm electrolytic cell for electrolysis, and obtaining sulfuric acid and lithium hydroxide products through electrolysis.
Step S7: and (4) heating the lithium hydroxide solution obtained in the step (S6) to 90-95 ℃, carbonizing, and performing solid-liquid separation to obtain a lithium carbonate product.
In example 1, the carbon loss after calcination was 2.1%, the purity of the lithium-rich solution after secondary impurity removal was 98%, the final recovery rate of lithium was 93%, and the purity of the regenerated lithium carbonate product was 99.5%
Example 2
The specific process is the same as that in example 1, the pre-oxidation roasting temperature in step S2 is changed to 450 ℃, other conditions are not changed, and according to the detection of the first mixed solution (i.e., the first filtrate) by the inductively coupled plasma spectrometry, the lithium leaching rate is slightly reduced to about 92%, the iron leaching rate is 15%, and under the condition, the carbon content is not lost.
Example 3
The specific process is the same as that in example 1, the solid-to-liquid ratio of the reaction system in step S3 is 1g, 8ml, and other conditions are unchanged, and according to the detection of the first mixed solution (i.e., the first filtrate) by inductively coupled plasma spectrometry, the lithium leaching rate is 90%, the iron leaching rates are all 16%, and the carbon content is basically unchanged.
Example 4
The specific process is the same as that in example 1, the pH of the impurity removal system in step S4 is changed to 6.5, other conditions are unchanged, and according to the detection of the first mixed solution (i.e., the first filtrate) by the inductively coupled plasma spectroscopic analysis method, the lithium leaching rate is above 95%, the iron leaching rate is 8%, the carbon content is basically unchanged, and the purity of the impurity-removed lithium-rich solution is 85%.
Example 5
The specific process is the same as that in example 1, the pH of the impurity removal system in step S5 is changed to 8.5, other conditions are not changed, and according to the detection of the first mixed solution (i.e., the first filtrate) by the inductively coupled plasma spectroscopic analysis method, the lithium leaching rate reaches 95%, the iron leaching rate is 8%, the carbon content is basically unchanged, and the purity of the impurity-removed lithium-rich solution is 93%.
Comparative example 1
The specific process is the same as that in example 1, the calcination temperature in step S3 is 600 ℃, other conditions are unchanged, and according to the detection of the first mixed solution (i.e., the first filtrate) by inductively coupled plasma spectrometry, the leaching rate of lithium is above 95%, the leaching rate of iron is still below 2%, and the loss of carbon is up to 48%.
Comparative example 2
The specific process is the same as that in example 1, the solid-to-liquid ratio of the reaction system in the step S3 is changed to 1:6, other conditions are not changed, and according to the detection of the first mixed solution (i.e., the first filtrate) by the inductively coupled plasma spectrometry, the lithium leaching rate is reduced to 85%, and the iron leaching rate is 18%.
Comparative example 3
The specific process is the same as that in example 1, the lithium hydroxide in step S4 is changed into sodium hydroxide, other conditions are not changed, the first mixed solution (namely, the first filtrate) is detected according to the inductively coupled plasma spectrometry, the lithium loss in the impurity removal process reaches 15%, and the purity of the regenerated lithium carbonate product is 92%
Comparative example 4
The specific process is the same as that in example 1, the pre-oxidation roasting temperature in step S2 is changed to 600 ℃, other conditions are not changed, and according to the detection of the first mixed solution (i.e., the first filtrate) by the inductively coupled plasma spectroscopy, the leaching rate of lithium is slightly increased, which is about 95%, the leaching rate of iron is 8%, the carbon loss is 31%, and the purity of the impurity-removed lithium-rich solution is 98%.
Comparative example 5
The specific process is the same as that in example 1, the lithium hydroxide in step S4 is changed into calcium hydroxide, other conditions are unchanged, and detection of the first mixed solution (i.e., the first filtrate) by inductively coupled plasma spectrometry results in 10% lithium loss and 94% purity of the regenerated product in the impurity removal process
Hereinbefore, specific embodiments of the present application are described with reference to the drawings. However, those skilled in the art will appreciate that various modifications and substitutions can be made to the specific embodiments of the present application without departing from the scope of the present application. Such modifications and substitutions are intended to be within the scope of the present application.