Method for removing calcium in rechargeable lithium battery recycling process
By employing a two-step calcium removal process, the problem of calcium removal in the recycling of rechargeable lithium batteries has been solved, and the generation of high-purity lithium compounds has been achieved, which is suitable for lithium extraction in the lithium battery recycling process.
Patent Information
- Application Number
- CN202510575553.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-05-07
- Filing Date
- 2025-05-06
- Publication Date
- 2025-11-07
AI Technical Summary
Existing technologies struggle to effectively remove calcium from rechargeable lithium battery recycling processes, resulting in high impurity content in liquid lithium and making it difficult to extract high-purity lithium compounds.
A two-step calcium removal process is adopted. First, an oxalate aqueous solution is added to an acidic lithium liquid to raise the pH value and form an alkaline liquid. Then, an ammonium oxalate aqueous solution is added to the alkaline liquid. Through two reactions, calcium ions are removed to generate high-purity lithium compounds.
It effectively removes calcium from the rechargeable lithium battery recycling process, generating high-purity lithium compounds, which are suitable as lithium sources for positive electrode active materials.
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Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a method of removing calcium in a rechargeable lithium battery recycling process. BACKGROUND
[0002] Rechargeable lithium batteries are rechargeable, and have three times or more energy density per unit weight than conventional lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, etc. Rechargeable lithium batteries can also be charged at a high rate, and thus are commercially manufactured for use in laptop computers, cellular phones, power tools, electric bicycles, etc. Moreover, active research and development are being conducted to further increase the energy density of rechargeable lithium batteries.
[0003] Rechargeable lithium batteries are manufactured by injecting an electrolyte into an electrode assembly including a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material.
[0004] Because lithium is a key raw material for rechargeable lithium batteries, the value of lithium has recently been increasing. In view of the increasing cost, many companies are conducting research on recycling lithium.
[0005] However, because the liquid obtained from the recycling process of rechargeable lithium batteries contains a large amount of impurities, it is difficult to extract lithium itself. In particular, calcium undergoes a resolubilization phenomenon in an alkaline solution state, and thus removing calcium from the liquid obtained from the recycling process of rechargeable lithium batteries has been an important task in the art. SUMMARY
[0006] Embodiments of the present disclosure effectively remove calcium from a liquid obtained in a recycling process of rechargeable lithium batteries and generate a high-purity lithium compound.
[0007] Some example embodiments provide a method of removing calcium in a rechargeable lithium battery recycling process, the method including: recovering an acidic lithium liquid including calcium from the recycling process; adding an aqueous oxalate solution to the acidic lithium liquid as a first calcium removal process; increasing a pH of the acidic lithium liquid to prepare an alkaline lithium liquid; and adding an aqueous ammonium oxalate solution to the alkaline lithium liquid as a second calcium removal process.
[0008] By the method according to the embodiments of the present disclosure, calcium can be effectively removed from a liquid obtained in a recycling process of rechargeable lithium batteries, and a high-purity lithium compound can be generated. DETAILED DESCRIPTION
[0009] In some example embodiments, a method of removing calcium in a rechargeable lithium battery recycling process (simply referred to as "the method of removing calcium") includes: recovering an acidic lithium liquor including calcium from a recycling process of a rechargeable lithium battery; adding an aqueous oxalate solution to the acidic lithium liquor as a first calcium removal process; increasing a pH of the acidic lithium liquor to prepare an alkaline lithium liquor; and adding an aqueous ammonium oxalate solution to the alkaline lithium liquor as a second calcium removal process.
[0010] In the method of removing calcium according to some example embodiments, calcium is removed twice in different pH ranges of a liquor obtained from a recycling process of a rechargeable lithium battery. Thus, calcium can be effectively removed and a high-purity lithium compound can be produced.
[0011] Hereinafter, the method of removing calcium according to example embodiments will be described in detail step by step.
[0012] Recovery process of acidic lithium liquor including calcium
[0013] The acidic lithium liquor including calcium can be recovered from a recycling process of a rechargeable lithium battery.
[0014] The acidic lithium liquor including calcium can have a pH of about 1 to about 5, or, in more specific embodiments, a pH of about 2 to about 4.
[0015] The acidic lithium liquor including calcium can further include lithium sulfate, lithium chloride, or a combination thereof. Calcium in the acidic lithium liquor including calcium can exist in an ionic state, and the amount of calcium ions can be about 1 ppm to about 10,000 ppm, about 1 ppm to about 1,000 ppm, or about 10 ppm to about 500 ppm.
[0016] First calcium removal process
[0017] After recovering the acidic lithium liquor including calcium, an aqueous oxalate solution can be added to the acidic lithium liquor as a first calcium removal process.
[0018] The step (or process) of the first calcium removal can be performed at about 0°C to about 80°C, about 30°C to about 70°C, or about 40°C to about 60°C. The aqueous oxalate solution can be added at a temperature of about 0°C to about 80°C, about 30°C to about 70°C, or about 40°C to about 60°C.
[0019] The concentration of the aqueous oxalate solution can be about 0.1 M to about 1 M. Such a concentration takes into account the content of calcium ions in the acidic lithium liquor including calcium.
[0020] In the step of the first calcium removal, calcium ions in the acidic lithium liquor react with oxalate ions and precipitate in the form of calcium oxalate. The calcium oxalate can be removed by using a filtration method widely known in the art.
[0021] pH adjustment process
[0022] By increasing the pH of the acidic lithium liquor after the first calcium removal process, a basic lithium liquor can be produced. To prepare the basic lithium liquor, sodium hydroxide, sodium carbonate, or a combination thereof can be used.
[0023] The basic lithium liquor can have a pH of about 7 to about 14 or a pH of about 8 to about 12.
[0024] Other impurity removal process
[0025] After the step of producing the basic lithium liquor, a step of removing iron, magnesium, zinc, or a combination thereof can be performed.
[0026] For example, about 1 part by weight to about 5 parts by weight of sodium carbonate (Na2C03) can be added to 100 parts by weight of the basic lithium liquor, and then a basic material such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH) can be added. Accordingly, a high purity lithium compound can be recovered in the final process.
[0027] Second calcium removal process
[0028] The step of the second calcium removal can be performed at about 40 °C to about 100 °C, about 50 °C to about 90 °C, or about 60 °C to about 80 °C. For this process, the aqueous ammonium oxalate solution can be added at a temperature of about 20 °C to about 90 °C, about 40 °C to about 85 °C, or about 60 °C to about 80 °C.
[0029] In the step of the second calcium removal, calcium ions in the basic lithium liquor react with oxalate ions and calcium is precipitated in the form of calcium oxalate. The calcium oxalate can be removed using a filtration method widely known in the art.
[0030] Post-treatment after calcium removal
[0031] After the step of the second calcium removal, a high purity lithium compound can be obtained in various forms.
[0032] For example, the method can further include adding a carbonate ion-containing material or carbon dioxide gas to the calcium-removed basic lithium liquor to produce lithium carbonate. The carbonate ion-containing material can be, for example, sodium carbonate (Na2C03).
[0033] In another example, the method can further include adding a hydroxide ion-containing material to the calcium-removed basic lithium liquor, concentrating, and crystallizing to produce lithium hydroxide. The hydroxide ion-containing material can be, for example, sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), etc.
[0034] The high-purity lithium compound obtained as described above can be used as a lithium source for a positive electrode active material. The method of preparing a positive electrode active material is a method widely known in the art.
[0035] Examples and comparative examples are described below. However, the following are merely examples of the present disclosure, and the present disclosure is not limited to the following examples.
[0036] Example 1
[0037] (1) Recovery process of acidic lithium liquor including calcium
[0038] An acidic lithium liquor including calcium was recovered from a recycling process of a rechargeable lithium battery. The acidic lithium liquor included 500 ppm of calcium ions and 15,000 Mg / L of lithium sulfate, and the pH value of the liquor was 2.
[0039] (2) First calcium removal process
[0040] A 0.5 M concentration of a sodium oxalate aqueous solution was prepared at 60°C, and then the sodium oxalate aqueous solution was added to the acidic lithium liquor while maintaining the same temperature.
[0041] The calcium ions in the acidic lithium liquor reacted with the oxalate ions to precipitate calcium oxalate. Then, the calcium oxalate was filtered to separate the solid and the liquid, and, after removing the solid, a liquor was obtained. Here, the obtained liquor will be referred to as "the once calcium-removed acidic lithium liquor".
[0042] (3) Other impurity removal process
[0043] After preparing the calcium-removed alkaline lithium liquor, 1 part by weight of sodium carbonate (Na2CO3, purity: 99%) was added based on 100 parts by weight of the alkaline lithium liquor to remove iron, magnesium, zinc, etc.
[0044] (4) pH value adjustment process
[0045] After removing the other impurities from the acidic lithium liquor, sodium hydroxide was added to increase the pH value to 11, and thus, "the once calcium-removed alkaline lithium liquor" was obtained.
[0046] (5) Second calcium removal process
[0047] An ammonium oxalate aqueous solution was prepared at a concentration of 0.5 M at 80°C, and then the ammonium oxalate aqueous solution was added to the alkaline lithium liquor while maintaining the same temperature.
[0048] The calcium ions in the alkaline lithium liquor reacted with the oxalate ions to precipitate calcium oxalate. Then, the calcium oxalate was filtered to separate the solid and the liquid, and, after removing the solid, a liquor was obtained. Here, the obtained liquor will be referred to as "the twice calcium-removed alkaline lithium liquor".
[0049] (6) Post-treatment after calcium removal
[0050] Sodium carbonate (Na2CO3) was added to the twice calcium-removed alkaline lithium liquor to obtain lithium carbonate.
[0051] Example 2
[0052] Lithium carbonate was prepared by twice removing calcium from an acidic lithium liquor including calcium in substantially the same manner as Example 1, except that the temperature of the first calcium removal process was changed to 40°C.
[0053] Example 3
[0054] Lithium carbonate was prepared by twice removing calcium from an acidic lithium liquor including calcium in substantially the same manner as Example 1, except that the temperature of the first calcium removal process was changed to 50°C.
[0055] Example 4
[0056] Lithium carbonate was prepared by twice removing calcium from an acidic lithium liquor including calcium in substantially the same manner as Example 1, except that the temperature of the second calcium removal process was changed to 70°C.
[0057] Example 5
[0058] Lithium carbonate was prepared by twice removing calcium from an acidic lithium liquor including calcium in substantially the same manner as Example 1, except that the temperature of the second calcium removal process was changed to 60°C.
[0059] Comparative Example 1 (Reference)
[0060] For an acidic lithium liquor including calcium obtained from a recycling process of rechargeable lithium batteries, lithium carbonate was prepared by adding sodium carbonate (Na2CO3) without a calcium removal process and without a pH adjustment process.
[0061] Comparative Example 2
[0062] For an acidic lithium liquor including calcium obtained from a recycling process of rechargeable lithium batteries, only the first calcium removal process was performed in substantially the same manner as Example 1, after which lithium carbonate was prepared by adding sodium carbonate (Na2CO3).
[0063] Comparative Example 3
[0064] For an acidic lithium liquor including calcium obtained from a recycling process of rechargeable lithium batteries, the pH adjustment process and the second calcium removal process were performed in substantially the same manner as Example 1 without the first calcium removal process, after which lithium carbonate was prepared by adding sodium carbonate (Na2CO3).
[0065] Comparative Example 4
[0066] For the acidic lithium liquid including calcium obtained from the recycling process of rechargeable lithium batteries, the first calcium removal process and the second calcium removal process were performed in substantially the same manner as in Example 1 without a pH adjustment process, after which lithium carbonate was prepared by adding sodium carbonate (Na2CO3).
[0067] For reference, the processes performed in Examples 1 to 5 and Comparative Examples 1 to 4 are summarized in Table 1.
[0068] (Table 1)
[0069]
[0070] Evaluation Example 1: Evaluation of calcium removal rate
[0071] In Comparative Example 1, the content of calcium ions in the acidic lithium liquid including calcium obtained from the recycling process of rechargeable lithium batteries was measured by using inductively coupled plasma (ICP). This measured value will be referred to as "first calcium ion content".
[0072] The content of calcium ions in each of the calcium-removed liquids according to Examples 1 to 5 and Comparative Examples 2 to 4 was measured in the same manner. This measured value will be referred to as "second calcium ion content".
[0073] The first calcium ion content and the second calcium ion content were substituted into Equation 1 to evaluate the calcium removal rate, and the results are shown in Table 2.
[0074] [Equation 1]
[0075] Calcium removal rate (%) = [(first calcium ion content) - (second calcium ion content)] / (first calcium ion content) x 100
[0076] Evaluation Example 2: Evaluation of lithium carbonate purity
[0077] The purity of lithium carbonate obtained in Examples 1 to 5 and Comparative Examples 1 to 4 was evaluated by using a lithium titration technique. The evaluation results are shown in Table 2.
[0078] (Table 2)
[0079] Calcium removal rate Lithium carbonate purity Example 1 99％ 99.99％ Example 2 99％ 99.99％ Example 3 99％ 99.99％ Example 4 99％ 99.99％ Example 5 99％ 99.99％ Comparative Example 1 (reference) 0％ 98％ Comparative Example 2 99％ 99.00％ Comparative Example 3 0％ 99.00％ Comparative Example 4 99％ 99.90％
[0080] Summary
[0081] Referring to Tables 1 and 2, Examples 1 to 5 effectively remove calcium and obtain a lithium compound having high purity, compared with the case where calcium is not removed (Comparative Example 1) or the case where calcium is removed once (Comparative Examples 2, 3).
[0082] On the other hand, Comparative Example 4, in which calcium is removed twice only in an acidic state without a pH adjustment process, shows an improved effect, but the effect is lower than Examples 1 to 5.
[0083] Accordingly, the calcium removal method according to the example embodiments (such as Examples 1 to 5), in which calcium is removed twice in different pH ranges of a liquid obtained from a recycling process of a rechargeable lithium battery, effectively remove calcium and provide a lithium compound having high purity.
[0084] While the disclosure has been described in connection with what is presently considered to be the example embodiments, it is to be understood that the application is not limited to the disclosed embodiments. On the contrary, the disclosure covers various modifications and equivalent arrangements.
Claims
1. A method of removing calcium in a recycling process of rechargeable lithium batteries, the method comprising: recovering an acidic lithium liquor including calcium from the recycling process; adding an aqueous oxalate solution to the acidic lithium liquor as a first calcium removal process; increasing a pH of the acidic lithium liquor to prepare a basic lithium liquor; and adding an aqueous ammonium oxalate solution to the basic lithium liquor as a second calcium removal process. The acidic lithium liquor has a pH of 1 to 5 before the pH is increased.
2. The method as recited in claim 1, wherein, The acidic lithium liquor includes at least one of lithium sulfate and lithium chloride.
3. The method as recited in claim 1, wherein, The calcium in the acidic lithium liquor exists in an ionic state and includes the calcium ion in an amount of 1 ppm to 10,000 ppm before the first calcium removal process.
4. The method as recited in claim 1, wherein, The aqueous oxalate solution has a concentration of 0.1 M to 1 M.
5. The method as recited in claim 1, wherein, The first calcium removal process is performed at a temperature range of 0 °C to 80 °C.
6. The method as recited in claim 1, wherein, Calcium is precipitated as calcium oxalate in the first calcium removal process.
7. The method as recited in claim 1, wherein, At least one of sodium hydroxide and sodium carbonate is used to prepare the basic lithium liquor.
8. The method as recited in claim 1, wherein, At least one of iron, magnesium, and zinc is removed after the basic lithium liquor is prepared.
9. The method as recited in claim 1, wherein, The basic lithium liquor has a pH of 7 to 14.
10. The method as recited in claim 1, wherein, The second calcium removal process is performed at a temperature range of 40 °C to 100 °C.
11. The method as recited in claim 1, wherein, Calcium is precipitated as calcium oxalate in the second calcium removal process.
12. The method as recited in claim 1, wherein, The method further includes adding a carbonate ion-containing material or carbon dioxide gas to the basic lithium liquor to produce lithium carbonate after the second calcium removal process.
13. The method as recited in claim 1, wherein, 14. The method as claimed in claim 1, wherein the method further includes adding a hydroxide ion-containing material to the basic lithium liquor, concentrating, and crystallizing to produce lithium hydroxide after the second calcium removal process.