Method for recovering lithium resources and applications thereof

Abstract

This invention provides a method and application for lithium resource recovery. The lithium resource recovery method involves adding lithium-containing material to a sulfate electrolyte, applying voltage, and performing an electrolytic lithium extraction reaction followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution. A precipitant is added to the lithium-containing solution, and after reaction, a lithium precipitate product is obtained. The lithium-containing material includes lithium iron phosphate. The inclusion of lithium iron phosphate in the lithium-containing material enables highly efficient and selective recovery of lithium from lithium iron phosphate. In-situ electrochemical oxidation of inexpensive sulfate to persulfate is used, and the generated persulfate oxidizes lithium iron phosphate to produce iron phosphate, releasing lithium ions into the solution. This invention also provides an application of the lithium resource recovery method in the treatment of spent lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a method and application for lithium resource recycling. Background Technology

[0002] Lithium iron phosphate (LiFePO4), a recently developed electrode material for lithium-ion batteries, is mainly used in power lithium-ion batteries as the positive electrode active material. It boasts advantages such as high discharge capacity, low cost, non-toxicity, and no environmental pollution. With the widespread use of lithium batteries, a large number of them have entered the failure and recycling stage. How to recycle lithium batteries and achieve resource recycling has become a matter of widespread social concern. Recycling lithium batteries not only solves a series of environmental problems caused by waste batteries but also recovers and utilizes the precious metals within the batteries, effectively alleviating resource scarcity.

[0003] In related technologies, some researchers use lithium iron phosphate as the positive electrode, metal or carbon electrodes as the negative electrode, and an aqueous solution as the electrolyte. An applied potential causes lithium ions from the positive electrode material to migrate into the electrolyte solution, forming a lithium-containing solution with a migration rate exceeding 90%. However, this method requires recoating spent lithium iron phosphate material onto the electrode, making the process complex. Other researchers add spent lithium iron phosphate material to an aqueous solution along with oxidants (persulfate, ozone, oxygen, hypochlorite, hydrogen peroxide) and stir. The lithium iron phosphate reacts with the oxidant to form iron phosphate, and lithium ions enter the solution, resulting in a pure lithium-containing solution and solid iron phosphate. However, the oxidants required for this process are expensive, increasing the overall cost.

[0004] Therefore, a new method for recovering lithium resources still needs to be developed. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a method for recovering lithium resources, which requires inexpensive reagents and raw materials and has low processing costs.

[0006] The present invention also provides an application of a lithium resource recycling method in the treatment of waste lithium-ion batteries.

[0007] The first aspect of the present invention provides a method for recovering lithium resources, comprising the following steps: adding lithium-containing materials to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product.

[0008] One technical solution of the present invention concerning a lithium resource recovery method has at least the following beneficial effects:

[0009] In the lithium resource recovery method of the present invention, lithium-containing materials are added to a sulfate electrolyte. The sulfate electrolyte has two functions: firstly, it provides raw materials for the oxidation of sulfate to persulfate; secondly, it can charge the electrolyte solute, thereby conducting electricity and promoting charge transfer.

[0010] While lithium extraction can still be achieved by directly adding persulfate instead of in-situ electrochemical oxidation of sulfate, firstly, the lithium leaching rate is not as good as that of in-situ electrochemical oxidation; secondly, persulfate is more expensive than sulfate, resulting in higher processing costs; and thirdly, in the lithium resource recovery method of this invention, sulfate is first electrochemically oxidized to persulfate, and then the persulfate reacts with lithium iron phosphate to produce sulfate again, thus achieving recycling.

[0011] In the lithium resource recovery method of the present invention, the lithium-containing material includes lithium iron phosphate, which can achieve efficient and selective recovery of lithium in lithium iron phosphate. In-situ electrochemical oxidation of inexpensive sulfate to persulfate is performed, and the generated persulfate oxidizes lithium iron phosphate to generate iron phosphate and releases lithium ions into the solution.

[0012] The lithium resource recovery method of this invention saves transportation costs, eliminates the danger of chemical storage, and allows for the recycling of sulfate ions.

[0013] According to some embodiments of the present invention, the lithium-containing material includes ternary lithium.

[0014] According to some embodiments of the present invention, the lithium-containing material includes at least one of lithium iron phosphate, lithium manganese oxide, and lithium cobalt oxide.

[0015] According to some embodiments of the present invention, the lithium-containing material may further include lithium-containing minerals and waste residue.

[0016] According to some embodiments of the present invention, the lithium iron phosphate is lithium iron phosphate powder.

[0017] According to some embodiments of the present invention, the concentration of the sulfate electrolyte is ≥0.1 mol / L.

[0018] According to some embodiments of the present invention, the concentration of the sulfate electrolyte is 0.1 mol / L to 4 mol / L.

[0019] According to some embodiments of the present invention, the sulfate electrolyte includes at least one of sodium sulfate electrolyte, potassium sulfate electrolyte, ammonium sulfate electrolyte and lithium sulfate electrolyte.

[0020] According to some embodiments of the present invention, the sulfate electrolyte comprises a soluble sulfate electrolyte.

[0021] Soluble sulfates are all acceptable, but ammonium sulfate is the most effective because the presence of ammonium ions can inhibit the anodic oxygen production reaction to some extent.

[0022] In addition to sulfate electrolytes, other reactive species that are prone to electrochemical oxidation, such as various halide salts, are also suitable.

[0023] According to some embodiments of the present invention, the voltage is ≥2V.

[0024] According to some embodiments of the present invention, the voltage is between 2V and 36V.

[0025] According to some embodiments of the present invention, the voltage is 2V to 15V.

[0026] According to some embodiments of the present invention, the voltage is 2V to 10V.

[0027] According to some embodiments of the present invention, the voltage is 2.1V to 10V.

[0028] According to some embodiments of the present invention, the voltage is 3V to 10V.

[0029] According to some embodiments of the present invention, the electrode for the electrolytic lithium extraction reaction is a metal electrode or a carbon electrode.

[0030] According to some embodiments of the present invention, stirring is performed during the electrolytic lithium extraction reaction.

[0031] According to some embodiments of the present invention, the precipitant includes at least one of phosphate and carbonate.

[0032] According to some embodiments of the present invention, the precipitant includes commonly used salts, such as ammonium salts, sodium salts, and potassium salts. It is sufficient to maintain consistency with sulfates, thereby better ensuring a relatively small number of cation types in the solution and minimizing the introduction of impurities during lithium precipitation.

[0033] According to some embodiments of the present invention, the phosphate includes at least one of ammonium phosphate, sodium phosphate, and potassium phosphate.

[0034] According to some embodiments of the present invention, the carbonate includes at least one of ammonium carbonate, sodium carbonate, and potassium carbonate.

[0035] A second aspect of the present invention provides the application of a lithium resource recycling method in the treatment of waste lithium-ion batteries.

[0036] The present invention relates to a technical solution for the application of a lithium resource recycling method in the treatment of waste lithium-ion batteries, which has at least the following beneficial effects:

[0037] The lithium resource recovery method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0038] A third aspect of the present invention provides a lithium resource recovery apparatus, the recovery apparatus comprising an electroleaching cell and a sedimentation cell connected in communication with the electroleaching cell.

[0039] One technical solution of the lithium resource recovery device of the present invention has at least the following beneficial effects:

[0040] The lithium resource recovery device of the present invention is simple in equipment, does not require complex process control, has undemanding reaction conditions, low production cost, and is easy to promote on a large scale.

[0041] In an electroleaching cell, lithium-containing materials are added to a sulfate electrolyte, a voltage is applied, and an electrolytic lithium extraction reaction is carried out. After solid-liquid separation, iron phosphate and a lithium-containing solution are obtained. A precipitant is added to the lithium-containing solution, and after reaction, a lithium precipitate product is obtained. The lithium-containing materials include lithium iron phosphate.

[0042] The sedimentation tank mainly contains a lithium-containing solution. A precipitant is added to the lithium-containing solution, and after the reaction, a lithium precipitate product is obtained. The lithium-containing material includes lithium iron phosphate.

[0043] When the lithium-containing material is lithium iron phosphate, the sulfate is first electro-oxidized to persulfate. The persulfate reacts with lithium iron phosphate to produce sulfate again. The sulfate flows back into the electroleaching cell, realizing the recycling of raw materials. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a lithium resource recycling device.

[0045] Figure 2 This is a flowchart of lithium resource recycling methods.

[0046] Figure 3 The results are XRD test results of lithium iron phosphate and iron phosphate in Example 1.

[0047] Figure 4 This refers to the leaching rates of lithium and iron in Example 1. Detailed Implementation

[0048] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0049] In some embodiments of the present invention, a method for recovering lithium resources is provided, comprising the following steps: adding lithium-containing materials to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product.

[0050] It is understood that in the lithium resource recovery method of the present invention, lithium-containing materials are added to the sulfate electrolyte. The sulfate electrolyte has two functions: firstly, it provides raw materials for the oxidation of sulfate to persulfate; secondly, it can charge the electrolyte solute, thereby conducting electricity and promoting charge transfer.

[0051] It is understandable that if persulfate is added directly instead of in-situ electrochemical oxidation of sulfate to persulfate, lithium can still be extracted. However, firstly, the lithium leaching rate is not as good as that of in-situ electrochemical oxidation; secondly, persulfate is more expensive than sulfate, resulting in higher process costs; and thirdly, in the lithium resource recovery method of this invention, sulfate is first electrochemically oxidized to persulfate, and then the persulfate reacts with lithium iron phosphate to produce sulfate again, thus achieving recycling.

[0052] It should be noted that ammonium sulfate costs approximately 950 yuan per ton, while persulfate costs approximately 5100 yuan per ton. Furthermore, the sulfate used in this invention can be recycled continuously. A rough estimate suggests that processing 1 ton of waste lithium iron phosphate requires only 43 kWh of renewable green electricity, at a cost of only 52 yuan per ton.

[0053] It should be noted that in the lithium resource recovery method of the present invention, the lithium-containing material includes lithium iron phosphate, which can achieve efficient and selective recovery of lithium in lithium iron phosphate. In-situ electrochemical oxidation of inexpensive sulfate into persulfate is performed, and the generated persulfate oxidizes lithium iron phosphate to generate iron phosphate, and releases lithium ions into the solution.

[0054] The lithium resource recovery method of this invention saves transportation costs, eliminates the danger of chemical storage, and allows for the recycling of sulfate ions.

[0055] In some embodiments of the present invention, the lithium-containing material includes ternary lithium.

[0056] In some embodiments of the present invention, the lithium-containing material includes at least one of lithium iron phosphate, lithium manganese oxide, and lithium cobalt oxide.

[0057] In some embodiments of the present invention, lithium iron phosphate is lithium iron phosphate powder.

[0058] In some embodiments of the present invention, the lithium-containing material may further include lithium-containing minerals and waste residue.

[0059] In some embodiments of the present invention, the concentration of the sulfate electrolyte is ≥0.1 mol / L.

[0060] It should be noted that the concentration of the sulfate electrolyte can be from 0.1 mol / L to a saturated solution.

[0061] In some embodiments of the present invention, the concentration of the sulfate electrolyte is 0.1 mol / L to 4 mol / L.

[0062] The higher the concentration of the sulfate electrolyte, the faster the leaching rate.

[0063] In some embodiments of the present invention, the sulfate electrolyte includes at least one of sodium sulfate electrolyte, potassium sulfate electrolyte, ammonium sulfate electrolyte, and lithium sulfate electrolyte.

[0064] It should be noted that sulfate electrolytes include soluble sulfate electrolytes.

[0065] It should also be noted that, in addition to sodium sulfate electrolyte, potassium sulfate electrolyte, ammonium sulfate electrolyte, and lithium sulfate electrolyte, virtually any soluble sulfate can be used. Because the presence of ammonium ions can inhibit the anodic oxygen production reaction to some extent, ammonium sulfate is the most effective.

[0066] It should be noted that, in addition to sulfate electrolytes, other reactive species that are prone to electrochemical oxidation, such as various halogen salts, are also applicable.

[0067] In some embodiments of the present invention, the voltage is ≥2V.

[0068] In some embodiments of the present invention, the voltage ranges from 2V to 36V.

[0069] In some embodiments of the present invention, the voltage is 2V to 15V.

[0070] In some embodiments of the present invention, the voltage is 2V to 10V.

[0071] In some embodiments of the present invention, the voltage is 2.1V to 10V.

[0072] In some embodiments of the present invention, the voltage is 3V to 10V.

[0073] In some embodiments of the present invention, the electrode for the lithium electrolytic extraction reaction is a metal electrode or a carbon electrode.

[0074] It should be noted that common electrode materials such as metals and carbon cloth are all applicable.

[0075] In some embodiments of the present invention, stirring is performed during the electrolytic lithium extraction reaction.

[0076] In some embodiments of the present invention, the precipitant includes at least one of phosphate and carbonate.

[0077] In some embodiments of the present invention, the precipitant includes commonly used salts, such as ammonium salts, sodium salts, and potassium salts. It is sufficient to maintain consistency with sulfates, thereby better ensuring a relatively small number of cations in the solution and minimizing the introduction of impurities during lithium precipitation.

[0078] In some embodiments of the present invention, the phosphate includes at least one of ammonium phosphate, sodium phosphate, and potassium phosphate.

[0079] In some embodiments of the present invention, the carbonate includes at least one of ammonium carbonate, sodium carbonate, and potassium carbonate.

[0080] In some embodiments of the present invention, the lithium resource recycling process is referenced. Figure 2 As shown.

[0081] In other embodiments of the present invention, the present invention provides the application of a lithium resource recycling method in the treatment of waste lithium-ion batteries.

[0082] It is understood that the lithium resource recovery method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0083] In other embodiments of the present invention, a lithium resource recovery apparatus is provided, with reference to... Figure 1 As shown, the recycling apparatus includes an electroleaching tank 100 and a sedimentation tank 200 connected to the electroleaching tank. This recycling apparatus can be used to implement the lithium resource recycling method of the present invention.

[0084] It is understood that the lithium resource recovery device of the present invention is simple in equipment, does not have complex process control, does not have harsh reaction conditions, has low production cost, and is easy to promote on a large scale.

[0085] In an electroleaching cell, lithium-containing materials are added to a sulfate electrolyte, a voltage is applied, and an electrolytic lithium extraction reaction is carried out. After solid-liquid separation, iron phosphate and a lithium-containing solution are obtained. A precipitant is added to the lithium-containing solution, and after reaction, a lithium precipitate product is obtained. The lithium-containing materials include lithium iron phosphate.

[0086] The sedimentation tank mainly contains lithium-containing solutions. A precipitant is added to the lithium-containing solution, and after the reaction, a lithium precipitate product is obtained. The lithium-containing materials include lithium iron phosphate.

[0087] When the lithium-containing material is lithium iron phosphate, the sulfate is first electro-oxidized to persulfate. The persulfate reacts with lithium iron phosphate to produce sulfate again. The sulfate flows back into the electroleaching cell, realizing the recycling of raw materials.

[0088] The technical solution of the present invention will be better understood below with reference to specific embodiments.

[0089] Example 1

[0090] A method for recovering lithium resources includes the following steps: adding lithium-containing material to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product, wherein the lithium-containing material is lithium iron phosphate.

[0091] The sulfate electrolyte is a 1 mol / L ammonium sulfate solution.

[0092] The amount of lithium iron phosphate added is 4g.

[0093] The positive and negative electrodes are platinum sheets.

[0094] Mechanical stirring was performed during the reaction, the reaction voltage was 10V, and the reaction time was 2h.

[0095] After the reaction was completed, the solution containing lithium and solid iron phosphate were obtained by filtration. The concentration of lithium in the solution was 3.5 g / L, the leaching rate was 99%, and no iron leaching was detected.

[0096] The lithium-containing material and the obtained iron phosphate solid were characterized by X-ray powder diffraction, and the results are as follows: Figure 3 As shown.

[0097] The leaching rates of lithium and iron are as follows: Figure 4 As shown, from Figure 4 It can be seen that the optimal efficiency of lithium leaching is greater than 90%.

[0098] Example 2

[0099] A method for recovering lithium resources includes the following steps: adding lithium-containing material to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product. The lithium-containing material is 4g of battery cathode material, which contains 3.4g of lithium iron phosphate.

[0100] The sulfate electrolyte is a 1 mol / L ammonium sulfate solution.

[0101] The positive and negative electrodes are made of carbon cloth.

[0102] Mechanical stirring was performed during the reaction, the reaction voltage was 10V, and the reaction time was 2h.

[0103] After the reaction was completed, the solution containing lithium and solid iron phosphate were obtained by filtration. The concentration of lithium in the solution was 3.0 g / L, the leaching rate was 99%, and no leaching of iron or aluminum was detected.

[0104] The obtained lithium-containing solution was concentrated to a Li2O content of 30 g / L, and a saturated ammonium phosphate solution was added to precipitate lithium. The precipitate was filtered, washed, and dried to obtain white crystals with a lithium phosphate purity of 99%.

[0105] Example 3

[0106] A method for recovering lithium resources includes the following steps: adding lithium-containing material to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product. The lithium-containing material is 4g of battery cathode material, which contains 3.4g of lithium iron phosphate.

[0107] The sulfate electrolyte is a 0.1 mol / L ammonium sulfate solution.

[0108] The positive and negative electrodes are made of carbon cloth.

[0109] Mechanical stirring was performed during the reaction, the reaction voltage was 10V, and the reaction time was 6h.

[0110] After the reaction was completed, the solution containing lithium and solid iron phosphate were obtained by filtration. The concentration of lithium in the solution was 3.4 g / L, the leaching rate was 99%, and no leaching of iron or aluminum was detected.

[0111] The obtained lithium-containing solution was concentrated to a Li2O content of 30 g / L, and a saturated ammonium phosphate solution was added to precipitate lithium. The precipitate was filtered, washed, and dried to obtain white crystals with a lithium phosphate purity of 99%.

[0112] Example 4

[0113] A method for recovering lithium resources includes the following steps: adding lithium-containing material to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product. The lithium-containing material is 4g of battery cathode material, which contains 3.4g of lithium iron phosphate.

[0114] The sulfate electrolyte is a 4 mol / L ammonium sulfate solution.

[0115] The positive and negative electrodes are made of carbon cloth.

[0116] Mechanical stirring was performed during the reaction, the reaction voltage was 10V, and the reaction time was 1h.

[0117] After the reaction was completed, the solution containing lithium and solid iron phosphate were obtained by filtration. The concentration of lithium in the solution was 3.0 g / L, the leaching rate was 99%, and no leaching of iron or aluminum was detected.

[0118] The obtained lithium-containing solution was concentrated to a Li2O content of 30 g / L, and a saturated ammonium phosphate solution was added to precipitate lithium. The precipitate was filtered, washed, and dried to obtain white crystals with a lithium phosphate purity of 99%.

[0119] Example 5

[0120] A method for recovering lithium resources includes the following steps: adding lithium-containing material to a sulfate electrolyte, applying voltage, performing an electrolytic lithium extraction reaction, followed by solid-liquid separation to obtain iron phosphate and a lithium-containing solution, adding a precipitant to the lithium-containing solution, and reacting to obtain a lithium precipitate product. The lithium-containing material is 4g of battery cathode material, which contains 3.4g of lithium iron phosphate.

[0121] The sulfate electrolyte is a 1 mol / L sodium sulfate solution.

[0122] The positive and negative electrodes are made of carbon cloth.

[0123] Mechanical stirring was performed during the reaction, the reaction voltage was 5V, and the reaction time was 4h.

[0124] After the reaction was completed, the solution containing lithium and solid iron phosphate were obtained by filtration. The concentration of lithium in the solution was 3.0 g / L, the leaching rate was 99%, and no leaching of iron or aluminum was detected.

[0125] The obtained lithium-containing solution was concentrated to a Li2O content of 30 g / L, and a saturated ammonium phosphate solution was added to precipitate lithium. The precipitate was filtered, washed, and dried to obtain white crystals with a lithium phosphate purity of 99%.

[0126] The lithium resource recovery method of this invention uses electrochemical oxidation to convert inexpensive sulfate solution into persulfate solution, which is then used for highly efficient and selective lithium extraction from lithium iron phosphate. Compared with existing processes, this method is simple to operate, inexpensive, has high leaching efficiency and high selectivity, and has good environmental and economic benefits.

[0127] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for recovering lithium resources, characterized in that, The process includes the following steps: Lithium iron phosphate is added to a sulfate electrolyte with a concentration of 0.1 mol / L to 4 mol / L, a voltage of 2V to 36V is applied, and after the lithium extraction reaction is carried out, solid-liquid separation is performed to obtain iron phosphate and a lithium-containing solution. A saturated ammonium phosphate solution is added to the lithium-containing solution as a precipitant, and after the reaction, a lithium precipitate product is obtained. After the lithium iron phosphate is added to the sulfate electrolyte and the voltage is applied, the sulfate is first electro-oxidized to persulfate, and then the persulfate reacts with lithium iron phosphate to produce sulfate again, thus realizing the recycling of sulfate. The sulfate electrolyte includes at least one of sodium sulfate electrolyte, potassium sulfate electrolyte, ammonium sulfate electrolyte, and lithium sulfate electrolyte.

2. The recycling method according to claim 1, characterized in that, The electrode used in the electrolytic lithium extraction reaction is a metal electrode or a carbon electrode.

3. The recycling method according to claim 1, characterized in that, During the electrolytic lithium extraction reaction, stirring is performed.

4. The application of the recycling method as described in any one of claims 1 to 3 in the treatment of waste lithium-ion batteries.

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