A method for preparing lithium dihydrogen phosphate by using waste lithium ion batteries

Abstract

The application provides a method for preparing lithium dihydrogen phosphate by using waste lithium ion batteries, comprising the following steps: obtaining lithium ion battery powder by processing the waste lithium ion batteries; using excessive concentrated phosphoric acid and hydrogen peroxide as an acid leaching system to leach lithium ions in the lithium ion battery powder by an oxidation acid leaching method, and filtering to obtain a leaching solution; using phosphoric acid dioctyl ester P204 and sulfonated kerosene after saponification treatment as extraction reagents, and allowing the leaching solution to be extracted and then to be separated into an aqueous phase solution and an organic phase solution; adding a trisodium phosphate solution into the aqueous phase solution to precipitate lithium phosphate, adding concentrated phosphoric acid into the lithium phosphate to perform acidification treatment, and obtaining a lithium dihydrogen phosphate solution. The method has excellent lithium extraction effect on different types of waste batteries, and can convert lithium resources in the waste batteries into battery-grade lithium dihydrogen phosphate products with high economic value through a simple process, fully utilizes lithium resources in the waste batteries, and has less "three wastes", small energy consumption and low economic cost.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium dihydrogen phosphate preparation, and in particular relates to a method for preparing lithium dihydrogen phosphate by utilizing waste lithium ion batteries. Background Art

[0002] Lithium iron phosphate (LIFP), a key lithium battery cathode material, is widely used in various new energy applications. Due to its excellent safety and cycle life, LFP batteries have become a mainstream power battery. Coupled with the rapid development of the energy storage industry, market demand for LFP has been surging in recent years. Current LFP production processes typically involve three sources: lithium, phosphorus, and iron. The lithium sources are typically lithium carbonate and lithium hydroxide, the phosphorus sources include ammonium dihydrogen phosphate, and the iron sources include ferrous oxalate and ferrous acetate. In recent years, a novel LFP synthesis process has gained increasing attention. This process uses LFP as both the lithium and phosphorus sources, successfully producing battery-grade LFP through the iron red process. Because LFP provides both lithium and phosphorus sources, the raw material cost of this process is significantly lower than other processes, making it increasingly popular among manufacturers. However, LFP synthesis methods typically require lithium carbonate and lithium hydroxide as lithium sources, which remains costly. Therefore, a new LFP production process is urgently needed.

[0003] On the other hand, since lithium batteries typically have a lifespan of 5 to 10 years, and my country's new energy vehicle industry entered a period of rapid development in 2018, the first wave of power battery scrapping is already approaching. Consequently, the market is flooded with discarded batteries, which, if not properly handled, will cause serious environmental pollution. Furthermore, discarded lithium batteries still contain significant amounts of lithium and other valuable elements, and failure to effectively recycle them will also result in significant economic losses. Consequently, attention has gradually shifted to the field of waste battery recycling.

[0004] There are many existing methods for recycling discarded lithium-ion batteries to produce lithium dihydrogen phosphate products. Most of these methods require high-temperature treatment or complex reagents, and have technical drawbacks such as environmental hazards or a narrow scope of application (e.g., only applicable to discarded lithium iron phosphate batteries). Therefore, there is a need to explore new process methods to meet the needs of processing different types of recycled waste battery materials and produce high-purity lithium dihydrogen phosphate products. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for preparing lithium dihydrogen phosphate using waste lithium ion batteries, aiming to solve at least one technical problem among the background technologies.

[0006] The present invention is achieved by a method for preparing lithium dihydrogen phosphate using waste lithium ion batteries, comprising the following steps:

[0007] Step 1: Crushing and screening

[0008] Collect waste lithium-ion batteries, split and crush them through a crusher, and sieve out lithium-ion battery powder through a sieve with an aperture of 0.05 to 0.1 mm. The waste lithium-ion batteries may be lithium iron phosphate, ternary NCM, lithium cobalt oxide, or lithium manganese oxide;

[0009] Step 2, digestion and extraction

[0010] The screened lithium-ion battery powder is collected and poured into a reactor, and concentrated phosphoric acid and 30% hydrogen peroxide solution are sequentially added to the reactor for digestion treatment, wherein the mass ratio of the concentrated phosphoric acid added to the lithium-ion battery powder is 5:1 to 7:1, and the mass ratio of the hydrogen peroxide solution added to the lithium-ion battery powder is 3:5 to 4:5. The reactor temperature is then controlled at 80 to 85° C. and stirring is continued for 0.5 to 1.5 hours. Finally, a leachate is filtered through a filter to obtain a leachate.

[0011] The present invention uses excess concentrated phosphoric acid and hydrogen peroxide as leaching reagents, which can extract lithium iron phosphate LiFePO4, ternary NCM LiNi x Co y The method selectively recovers lithium from cathode waste materials of different waste lithium-ion batteries, such as MnzO2, lithium cobalt oxide LiCoO2, and lithium manganese oxide LiMn2O4, and converts them into soluble lithium salts. Compared with other inorganic strong acid systems (such as excess sulfuric acid + excess oxidant or excess hydrochloric acid + excess oxidant) for leaching, this method can achieve highly selective lithium recovery from different types of cathode waste materials in one step; compared with the conventional combination system of dilute phosphoric acid and hydrogen peroxide, the present invention can reduce the precipitation of elements such as nickel, cobalt, and manganese, thereby ensuring the purity of the recovered lithium.

[0012] Step 3: Purification and removal of impurities

[0013] The extraction organic phase reagent is obtained by mixing dioctyl phosphate P204 and sulfonated kerosene in a volume ratio of 1:8-10, and a sodium hydroxide solution is added to saponify the extraction organic phase reagent, and the saponification rate is controlled to be 30%-70%. The saponified extraction organic phase reagent is used as an extraction reagent, and the saponification treatment improves the extraction ability of the extraction agent P204;

[0014] According to the volume ratio of leachate: extraction reagent = 1:1 to 1:1.2, the extracted organic phase reagent is added to the leachate, and the mixture is stirred continuously for 0.5 to 1.5 hours to fully extract the impurity elements in the solution. After the extraction is completed, the mixture is allowed to stand for 2 to 4 hours to allow natural stratification. The aqueous phase solution and the organic phase solution are discharged successively through the bottom pipe of the reactor, wherein the aqueous phase solution is the lithium-containing purification solution, and the organic phase solution is the extraction solution containing many impurity elements;

[0015] The main impurity elements in the leachate are Ni 2+ 、Mn 2+ 、Co 2+ The present invention adopts a one-step extraction method to replace the step-by-step precipitation of impurities (DMG complex precipitation Ni 2+ 、KMnO4 oxidation precipitation Mn 2+ , oxalic acid precipitated Co 2+ ) or lithium precipitation removal + extraction secondary removal of impurities, which simplifies the purification steps and improves the impurity removal efficiency.

[0016] Step 4: Reagent lithium precipitation and phosphoric acidification

[0017] adding trisodium phosphate solution to the lithium-containing purified liquid and filtering to obtain lithium phosphate precipitate; adding concentrated phosphoric acid to the lithium phosphate precipitate for acidification, controlling the pH value of the solution to 1-2, and obtaining lithium dihydrogen phosphate solution;

[0018] Step 5, Concentration and Crystallization

[0019] The lithium dihydrogen phosphate solution obtained in step 4 is evaporated, concentrated, and crystallized, and then filtered and dried to obtain a battery-grade lithium dihydrogen phosphate product;

[0020] Step 6, Reagent Recovery

[0021] The organic phase solution obtained in step 3 is pickled with acid to wash out numerous impurity metal elements for purification. The purified organic phase can then be reused in step 3 as an extraction reagent, thereby achieving the purpose of recycling the organic solution and reducing pollution and costs. The acid can be hydrochloric acid, sulfuric acid, or phosphoric acid.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention proposes a novel method for recovering lithium from waste lithium-ion batteries. Concentrated phosphoric acid and hydrogen peroxide are used as the acid leaching system to leach lithium, and dioctyl phosphate (P204) is used as the extractant. Impurity elements in the waste batteries are treated by extraction and purification. The obtained lithium-containing purified liquid is then subjected to sodium phosphate precipitation and phosphoric acid acidification to obtain a battery-grade lithium dihydrogen phosphate product with high economic value.

[0024] 2. The present invention solves the problem in the prior art that only specific types of lithium battery waste can be processed by specific processes, resulting in low lithium extraction efficiency and low economic value. It can effectively recover precious lithium metal elements from various types of waste lithium batteries and produce battery-grade lithium dihydrogen phosphate products with high purity and high economic value through a simple method.

[0025] 3. The entire process of the present invention produces less "three wastes", has low energy consumption, and is economical and environmentally friendly.

[0026] 4. The extraction reagents in the preparation process of the present invention can be recycled and reused, which effectively reduces economic costs and resource waste and reduces environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the method for preparing lithium dihydrogen phosphate using waste lithium ion batteries. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] like Figure 1 As shown, the method for preparing lithium dihydrogen phosphate using waste lithium ion batteries includes the following steps:

[0030] (1) Crushing and screening

[0031] Collect waste lithium-ion batteries, split and crush them through a crusher, and sieve out lithium-ion battery powder through a sieve, wherein the sieve aperture is 0.05-0.1mm. The waste lithium-ion batteries can be lithium iron phosphate, ternary NCM, lithium cobalt oxide, and lithium manganese oxide.

[0032] (2) Digestion and extraction

[0033] The screened lithium-ion battery powder is collected and poured into a reactor, and concentrated phosphoric acid and 30% hydrogen peroxide solution are sequentially added to the reactor for digestion treatment, wherein the mass ratio of the concentrated phosphoric acid added to the lithium-ion battery powder is 5:1-7:1, and the mass ratio of the hydrogen peroxide solution added to the battery powder is 3:5-4:5. Subsequently, the reactor temperature is controlled at 80-85° C. and stirring is continued for 0.5-1.5 hours. Finally, a leachate is filtered through a filter to obtain a leachate.

[0034] Taking ternary NCM waste lithium-ion batteries as the object, the effects of leaching conditions such as concentrated phosphoric acid dosage (mass ratio to lithium-ion battery powder is 1:1-10:1), hydrogen peroxide dosage (mass ratio to lithium-ion battery powder is 1:5-6:5), reaction temperature (30-100℃), and reaction time (10-120min) on the leaching rate of cathode active materials in waste ternary lithium-ion batteries were explored.

[0035] The effect of the amount of concentrated phosphoric acid on the performance of various metal ions (Li + 、Ni 2+ 、Mn 2+ 、Co 2+ ) leaching rate, in this process, other reaction conditions remain unchanged, such as the mass ratio of hydrogen peroxide to lithium-ion battery powder is 3:5, the reactor temperature is 80℃, and the reaction time is 60min. As the amount of concentrated phosphoric acid increases, Li + The leaching efficiency continues to increase. When the mass ratio of concentrated phosphoric acid to lithium-ion battery powder is 5:1 to 7:1, the leaching efficiency can reach more than 99%. When the dosage is greater than 7:1, that is, the dosage continues to increase, the leaching efficiency of Li + The leaching efficiency was not significantly affected.

[0036] The same experimental method was used to explore the effects of hydrogen peroxide dosage, reaction temperature and reaction time on the metal ions (Li + 、Ni 2+ 、Mn 2+ 、Co 2+ ) leaching efficiency, the appropriate mass ratio of hydrogen peroxide solution to battery powder is 3:5-4:5, the reaction temperature is 80-85℃, the reaction time is 30-90min, Li + The experiment found that if the amount of hydrogen peroxide is excessive, the reaction temperature is too high (over 85 ° C), and the reaction time is too long (over 90 min) in the concentrated phosphoric acid system, Ni 2+ 、Mn 2+ 、Co 2+ The precipitation efficiency will increase significantly, such as Mn 2+ The leaching rate of ions is as high as over 95%.

[0037] (3) Purification and removal of impurities

[0038] Dioctyl phosphate P204 and sulfonated kerosene are mixed in a volume ratio of 1:8-10 to obtain an extraction organic phase reagent, and a sodium hydroxide solution is added to saponify the extraction organic phase reagent to control the saponification rate to 30%-70%. The saponified extraction organic phase reagent is used as an extraction reagent, and the saponification treatment improves the extraction ability of the extraction agent P204. The saponified extraction organic phase reagent is added to the leachate in a volume ratio of leachate:extraction reagent = 1:1-1:1.2, and the mixture is continuously stirred for 0.5-1.5 hours to fully extract the impurity elements in the solution. After the extraction is completed, the mixture is allowed to stand for 2-4 hours to allow natural stratification, and the aqueous phase solution and the organic phase solution are discharged successively through a pipeline at the bottom of the reactor, wherein the aqueous phase solution is a lithium-containing purification solution, and the organic phase solution is an extraction solution containing numerous impurity elements.

[0039] Taking the leachate extraction obtained by treating the ternary NCM waste lithium-ion battery in step (2) as the object, the effects of the mixing ratio of P204 and sulfonated kerosene (1:6~12), saponification rate (20%~80%), extraction reagent dosage (leachate: extraction reagent = 1:0.8~1:1.4), and extraction time (10min~120min) on the lithium extraction efficiency were explored.

[0040] The effect of the extraction reagent on lithium extraction efficiency was investigated within a volume ratio of 1:6 to 12 between dioctyl phosphate (P204) and sulfonated kerosene. Other reaction conditions remained unchanged, such as a saponification rate of 50%, a leachate:extraction reagent ratio of 1:1.1, and a reaction time of 60 minutes. Lithium extraction efficiency was improved when the volume ratio of the extractant, dioctyl phosphate (P204), to the diluent, sulfonated kerosene, was 1:8 to 10, with the optimal value being 1:9. Similarly, higher extraction efficiency was found when the saponification rate was between 30% and 70%, the volume ratio of the leachate:extraction reagent was 1:1 to 1:1.2, and the extraction time was between 0.5 and 1.5 hours.

[0041] (4) Reagent lithium precipitation and phosphoric acidification

[0042] Trisodium phosphate solution is added to the lithium-containing purified liquid, and the solution is filtered to obtain lithium phosphate precipitate; concentrated phosphoric acid is added to the lithium phosphate precipitate for acidification, and the pH value of the solution is controlled to be 1-2 to obtain a lithium dihydrogen phosphate solution.

[0043] (5) Concentration and crystallization

[0044] The obtained lithium dihydrogen phosphate solution is evaporated, concentrated and crystallized, and then filtered and dried in sequence to obtain a battery-grade lithium dihydrogen phosphate product.

[0045] Example 1

[0046] The method for preparing lithium dihydrogen phosphate using waste lithium iron phosphate batteries comprises the following steps:

[0047] Step 1: Collect waste lithium iron phosphate batteries, crush them with a crusher, and sieve out the battery powder through a sieve with a pore size of 0.1 mm;

[0048] Step 2: Pour the sieved battery powder into a reactor, and add concentrated phosphoric acid and 30% hydrogen peroxide solution to the reactor in sequence to digest it, wherein the mass ratio of concentrated phosphoric acid to battery powder is 7:1, and the mass ratio of hydrogen peroxide solution to battery powder is 4:5. Then control the reactor temperature to 85°C and continue stirring for 1 hour, and finally filter through a filter to obtain a leachate;

[0049] Step 3: adding a mixed solution of P204 and sulfonated kerosene to the leachate, stirring continuously for 1 hour to fully extract the impurity elements in the solution, and then standing for 3 hours to allow natural stratification; wherein the volume ratio of the leachate to the P204-sulfonated kerosene mixed solution is controlled at 1:1.2; and in the P204-sulfonated kerosene mixed solution, the volume ratio of the extractant P204 to the diluent sulfonated kerosene is 1:9; in addition, in order to improve the extraction ability of the extractant P204, the P204 and sulfonated kerosene mixed solution is saponified with sodium hydroxide before use, and the saponification rate is controlled to 70%; after the extraction is completed, the aqueous phase solution and the organic phase solution are discharged successively through the bottom pipe of the kettle, wherein the aqueous phase solution is a lithium-containing purified solution, and the organic phase solution is an extract containing numerous impurity elements;

[0050] Step 4: adding trisodium phosphate solution to the lithium-containing purified liquid and filtering to obtain a lithium phosphate precipitate; adding concentrated phosphoric acid to the lithium phosphate precipitate for acidification, controlling the pH value of the solution to 1.5, and obtaining a lithium dihydrogen phosphate solution;

[0051] Step 5, concentration and crystallization: evaporating and concentrating the lithium dihydrogen phosphate solution obtained in step 4 and crystallizing it, followed by filtering and drying to obtain a battery-grade lithium dihydrogen phosphate product;

[0052] This embodiment can also recycle and reuse the extraction reagent. Specifically, the organic phase solution obtained in step 3 is pickled with sulfuric acid to wash out many impurity metal elements. The purified organic phase can then be reused in step 3, achieving the purpose of recycling the organic solution, reducing pollution and lowering costs.

[0053] Example 2

[0054] The type of waste lithium-ion battery in step 1 is changed to ternary NCM, and the other steps are the same as in Example 1.

[0055] Example 3

[0056] Change the type of waste lithium-ion batteries in step 1 to lithium manganate;

[0057] The mass ratio of concentrated phosphoric acid added in step 2 to battery powder was changed to 5:1, the mass ratio of hydrogen peroxide solution added to battery powder was 3:5, and the reactor temperature was controlled at 80°C;

[0058] The volume ratio of the leaching solution in step 3 to the P204-sulfonated kerosene mixed solution was controlled at 1:1.1; the saponification rate became 50%;

[0059] Other steps are the same as in Example 1.

[0060] Example 4

[0061] Change the type of waste lithium-ion batteries in step 1 to lithium cobalt oxide;

[0062] Other steps are the same as in Example 3.

[0063] Example 5

[0064] The mass ratio of concentrated phosphoric acid added in step 2 to battery powder was changed to 6:1, and the mass ratio of hydrogen peroxide solution added to battery powder was changed to 3.5:5;

[0065] The volume ratio of the leaching solution in step 3 to the P204-sulfonated kerosene mixed solution was controlled at 1:1; the saponification rate became 30%;

[0066] Other steps are the same as in Example 1.

[0067] Comparative Example 1

[0068] The extraction reagent in step 3 was replaced with an ion exchange resin, and the other steps were the same as in Example 1. The two products were compared. This comparison revealed that the ion exchange resin was unable to completely remove nickel or cobalt present in the form of metal extracts. This incomplete removal of impurities such as nickel and cobalt compromised the purity of the final product and significantly increased the difficulty in handling the evaporated crystallization mother liquor.

[0069] Comparative Example 2

[0070] The extraction reagents in step 3 were replaced with P204+P507+sulfonated kerosene for a synergistic extraction, with the weight ratio of P204:P507 being 3:2. The other steps were the same as in Example 1, and the two products were compared. This comparison revealed that the impurity removal efficiency of this comparative example was slightly lower than that of Example 1, resulting in slightly lower product purity. P204 is more acidic than P507, resulting in a more complete saponification process, dissociating the largest number of organophosphate ions, which in turn accelerates the extraction reaction rate. Furthermore, P204 is less expensive than P507.

[0071] The purity of the lithium dihydrogen phosphate products obtained in Examples 1 to 5 and Comparative Examples 1 to 2 was tested, and the results were as follows:

[0072] Table 1: Purity of the lithium dihydrogen phosphate product obtained in each embodiment

[0073] product purity(%) Example 1 99.78 Example 2 99.67 Example 3 99.82 Example 4 99.86 Example 5 99.73 Comparative Example 1 96.55 Comparative Example 2 99.62

[0074] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing lithium dihydrogen phosphate using waste lithium ion batteries, characterized in that: The specific steps of the method are as follows: Splitting, crushing and screening waste lithium-ion batteries to obtain lithium-ion battery powder; Lithium ions in lithium-ion battery powder are leached by oxidative acid leaching, followed by solid-liquid separation to obtain a leachate, wherein the oxidative acid leaching method uses excess concentrated phosphoric acid and hydrogen peroxide as an acid leaching system; The leaching solution is purified and impurities removed using saponified dioctyl phosphate P204 and sulfonated kerosene as extraction reagents, and after extraction, the solution is allowed to stand and separate into an aqueous phase solution and an organic phase solution; A trisodium phosphate solution is added to the aqueous phase solution to precipitate lithium to obtain a lithium phosphate precipitate, and concentrated phosphoric acid is added to the lithium phosphate precipitate for acidification to obtain a lithium dihydrogen phosphate solution.

2. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 1, wherein: The method further includes concentration and crystallization, specifically: evaporating, concentrating and crystallizing the lithium dihydrogen phosphate solution, and then filtering and drying in sequence to obtain a battery-grade lithium dihydrogen phosphate product.

3. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 1, wherein: The method further includes extracting agent recovery, specifically: adding acid solution to the organic phase solution for pickling, thereby purifying and removing metallic impurity elements; the purified organic solution can be used as an extraction agent.

4. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 3, characterized in that: The acid solution is hydrochloric acid, sulfuric acid or phosphoric acid.

5. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 1, wherein: The particle size of the lithium ion battery powder is 0.05-0.1 mm; the waste lithium ion battery is lithium iron phosphate, ternary NCM, lithium cobalt oxide or lithium manganese oxide.

6. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 1, characterized in that: The preparation steps of the leachate are specifically as follows: pouring the lithium-ion battery powder into an acid-resistant reactor, sequentially adding concentrated phosphoric acid and 30% hydrogen peroxide solution into the reactor for digestion treatment, controlling the reactor temperature at 80-85° C. and continuously stirring for 0.5-1.5 hours during the process, and finally filtering to obtain the leachate.

7. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 6, characterized in that: The mass ratio of the concentrated phosphoric acid dosage to the lithium ion battery powder is 5:1 to 7:1, and the mass ratio of the hydrogen peroxide solution dosage to the lithium ion battery powder is 3:5 to 4:

5.

8. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 1, characterized in that: The steps of purifying and removing impurities from the leachate are specifically as follows: P204 and sulfonated kerosene are mixed in a set ratio to obtain an extraction organic phase reagent, and the extraction organic phase reagent is saponified with a sodium hydroxide solution to obtain a saponified extraction organic phase reagent as an extraction reagent; Add the saponified organic phase extraction reagent to the leachate and stir continuously for 0.5-1.5 hours to fully extract the impurity elements in the solution, then let it stand for 2-4 hours to allow it to naturally separate. The natural stratification obtains an aqueous phase solution mainly containing a lithium purification solution and an organic phase solution mainly containing an extraction reagent containing impurity elements.

9. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 8, characterized in that: The volume ratio of the P204 to the sulfonated kerosene is 1:8-10; the saponification rate is 30%-70%; and the volume ratio of the leaching solution to the saponified extraction organic phase reagent is controlled at 1:1-1.

2.

10. The method for preparing lithium dihydrogen phosphate using waste lithium ion batteries according to claim 1, characterized in that: During the acidification treatment, concentrated phosphoric acid is added to control the pH value of the solution to be 1-2.

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