CN114759285B - Treatment method of leachate from waste lithium-ion batteries - Google Patents

Abstract

The invention belongs to the technical field of battery recovery, and discloses a treatment method of waste lithium ion battery leaching liquid, which comprises the following steps: adding a complexing agent into the leaching solution of the waste lithium ion battery, and constructing an electrolytic tank with an electrolytic counter electrode; and alternately applying asymmetric forward voltage and reverse voltage to the electrolytic tank until the concentration of impurity metal ions in the leaching solution of the waste lithium ion battery reaches the expected value. The method for removing the metal impurity ions in the lithium ion battery leaching solution can solve the problems of low impurity removal efficiency, serious loss of valuable metal lithium and great environmental pollution in the prior art.

Description

Treatment method of leachate from waste lithium-ion batteries

Technical Field

The invention belongs to the technical field of battery recycling, and in particular relates to purification and impurity removal of lithium-containing leaching solution.

Background technique

The recycling of waste lithium-ion batteries is an inevitable requirement for the country to achieve long-term sustainable development. At present, the method used by battery companies to deal with waste lithium-ion batteries is: first, the positive electrode powder is obtained through pretreatment, and then the positive electrode powder is heat-treated to obtain the roasted material. The roasted material is subjected to acid leaching, washing, impurity removal, extraction, lithium precipitation and other steps to obtain battery-grade lithium carbonate and other valuable metal salts. In order to obtain high-purity battery-grade lithium carbonate (YST 582-2006), the impurity removal process is complicated and the process is cumbersome, such as sodium sulfide to remove copper ions, sodium fluoride to remove aluminum ions, hydrogen peroxide and ammonia water to remove iron ions, etc. A variety of additives are used in the impurity removal process, the valuable element lithium loss is large, the economic benefits are low, and the environmental pollution is serious.

Summary of the invention

In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for treating waste lithium-ion battery leachate with a simple process flow, being green and pollution-free, having a high efficiency in removing impurity ions and having a small loss of valuable element lithium.

The waste lithium-ion batteries are discharged, disassembled, current collector removed, and floated to obtain the positive electrode active material powder of the waste lithium-ion batteries; the positive electrode active material powder of the waste lithium-ion batteries is leached by a wet method to obtain a waste lithium-ion battery leachate containing lithium ions and a small amount of impurity metal ions such as Al ³⁺ , Cu ²⁺ , Fe ²⁺ , and Fe ³⁺ .

To achieve the above objectives, the present invention specifically provides the following technical solutions.

A method for treating waste lithium ion battery leachate comprises the following steps: adding a complexing agent to the waste lithium ion battery leachate, and constructing an electrolytic cell with an electrolytic counter electrode; and alternately applying an asymmetric forward voltage and a reverse voltage to the electrolytic cell until the concentration of impure metal ions in the waste lithium ion battery leachate reaches an expected value.

The complexing agent forms a negatively charged complex with the impurity metal ions. By applying a positive voltage, the negatively charged impurity metal complex and the lithium ions migrate in opposite directions, forming lithium ion-rich areas and impurity ion-rich areas at the cathode and cathode, respectively. When a reverse voltage is applied, the carbon rod electrode in the impurity ion-rich area obtains electrons, a reduction reaction occurs, and the impurity metal ions are reduced and deposited on the carbon rod electrode; the carbon rod electrode in the lithium ion-rich area loses electrons, an oxidation reaction occurs, and water decomposes to produce oxygen.

Furthermore, in some preferred embodiments of the present invention, the chelating agent is at least one of EDTA (ethylenediaminetetraacetic acid), EDTA-2Na (disodium ethylenediaminetetraacetate), STPP (sodium tripolyphosphate), and H-501 (organic polyphosphate polymer), and EDTA is more preferred.

Furthermore, in some preferred embodiments of the present invention, the ratio of the added molar amount of the complexing agent to the molar amount of the impurity metal ions is 0.3-1.2:1.

Furthermore, in some preferred embodiments of the present invention, the counter electrode is a modified carbon rod electrode or an inert electrode.

Furthermore, the inert electrode is a platinum electrode.

It is further preferred that the counter electrode is a modified carbon rod electrode, which can increase the reduction potential of impurity metal ions.

Furthermore, in some preferred embodiments of the present invention, the forward voltage is 3-7V, preferably 3-5V; the reverse voltage is 6-14V, preferably 10-14V.

Further, in some preferred embodiments of the present invention, the duration of the forward voltage is shorter than the duration of the reverse voltage.

Furthermore, the duration of the forward voltage is 0.2-0.7 ms, and the duration of the reverse voltage is 1-3 ms.

Furthermore, in some preferred embodiments of the present invention, the following steps are also included: introducing CO ₂ into the waste lithium ion battery leachate with the impurity metal ion concentration less than 10 ppm, then evaporating and concentrating to obtain lithium carbonate and a concentrated solution containing a complexing agent; and recycling the concentrated solution containing a complexing agent.

The present invention removes impure metal ions in the leachate of waste lithium-ion batteries by applying an asymmetric alternating voltage, which has the following obvious beneficial effects:

(1) The process of separating and purifying the leachate from waste lithium-ion batteries is simple, avoiding the use of a large number of chemical additives in the traditional chemical precipitation process, which is green and environmentally friendly. At the same time, it greatly reduces the cost of separation and purification, and has great economic benefits;

(2) It has a good removal effect on various metal ion impurities that may be contained in the leachate of waste lithium-ion batteries, such as Cu ²⁺ , Al ³⁺ , Fe ²⁺ , Fe ³⁺ , Ni ²⁺ , Co ²⁺ , Mn ²⁺ , Ca ²⁺ , Mg ^{2+, etc.} , and the whole process will not cause lithium element loss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of applying an asymmetric alternating voltage.

Detailed ways

The present invention is described in detail below in conjunction with the accompanying drawings. The description in this part is only exemplary and explanatory and should not have any limiting effect on the protection scope of the present invention.

It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the invention belongs.

FIG1 is a schematic diagram of applying an asymmetric alternating voltage in the following embodiment, where a forward voltage and a reverse voltage are applied alternately and repeatedly.

Example 1

The contents of major metal ions in the leachate of waste lithium batteries to be treated are shown in Table 1.

Table 1

6 g of EDTA solid was added to 100 ml of waste lithium-ion battery leachate, and stirred in a 60 °C water bath to dissolve. Then, an electrolytic cell was formed with a modified carbon rod electrode having an amidoxime functional group. A forward voltage of 5 V was applied to the electrolytic cell for 0.5 ms, and a reverse voltage of 10 V was applied for 2 ms, alternately and repeatedly, for 30 min. The concentrations of the main metal ions in the waste lithium-ion battery leachate were detected, and the results are shown in Table 2.

Table 2

Comparing the data in Table 1 and Table 2, it can be found that the removal rate of Li ⁺ is 0.16%, the removal rate of Cu2 ⁺ is 99.54%, the removal rate of Al3 ⁺ is 73.03%, and the removal rate of Fe ions is 97.51%. The removal rate of impurity ions is very high, and the loss of valuable lithium is extremely small.

Example 2

The contents of major metal ions in the leachate of waste lithium batteries to be treated are shown in Table 3.

table 3

Add 6 g of EDTA-2Na solid to 100 ml of waste lithium-ion battery leachate and stir to dissolve at room temperature. Then form an electrolytic cell with a modified carbon rod electrode having an amidoxime functional group. Apply a forward voltage of 6 V to the electrolytic cell for 0.4 ms, and then apply a reverse voltage of 13 V for 1.5 ms, alternately and repeatedly for 30 min. The concentration of the main metal ions in the waste lithium-ion battery leachate was detected, and the results are shown in Table 4.

Table 4

Comparing the data in Table 3 and Table 4, it can be found that the removal rate of Li ⁺ is 0.25%, the removal rate of Cu2 ⁺ is 99.56%, the removal rate of Al3 ⁺ is 79.81%, and the removal rate of Fe ions is 96.03%. The removal rate of impurity ions is very high, and the loss of valuable lithium is extremely small.

Example 3

The contents of major metal ions in the leachate of waste lithium batteries to be treated are shown in Table 5.

table 5

7 g of STPP solid was added to 100 ml of waste lithium-ion battery leachate, and stirred in a water bath at room temperature to dissolve. Then, an electrolytic cell was formed with a modified carbon rod electrode having an amidoxime functional group. A forward voltage of 4 V was applied to the electrolytic cell for 0.7 ms, and a reverse voltage of 7 V was applied for 3 ms, alternating and repeating for 30 min. The concentrations of the main metal ions in the waste lithium-ion battery leachate were detected, and the results are shown in Table 6.

Table 6

Comparing the data in Table 5 and Table 6, it can be found that the removal rate of Li ⁺ is 0.14%, the removal rate of Cu2 ⁺ is 99.57%, the removal rate of Al3 ⁺ is 46.98%, and the removal rate of Fe ions is 63.81%. The removal rate of impurity ions is very high, and the loss of valuable lithium is extremely small.

Example 4

The contents of major metal ions in the leachate of waste lithium batteries to be treated are shown in Table 7.

Table 7

6 g of EDTA solid was added to 100 ml of waste lithium-ion battery leachate, and stirred in a 60 °C water bath to dissolve. Then, an electrolytic cell was formed with a modified carbon rod electrode having an amidoxime functional group. A forward voltage of 5 V was applied to the electrolytic cell for 0.5 ms, and a reverse voltage of 10 V was applied for 2 ms, alternately and repeatedly, for 30 min. The concentrations of the main metal ions in the waste lithium-ion battery leachate were detected, and the results are shown in Table 8.

Table 8

By comparing the data in Table 7 and Table 8, it can be found that the removal rate of Li ⁺ is 0.19%, the removal rate of Cu2 ⁺ is 99.55%, the removal rate of Al3 ⁺ is 72.20%, the removal rate of Fe ions is 99.48%, the removal rate of Ni2 ⁺ is 81.02%, the removal rate of Co2 ⁺ is 87.20%, and the removal rate of Mn2 ⁺ is 85.59%. The removal rate of impurity ions is very high, and the loss of valuable lithium is extremely small.

The present invention is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solution of the present invention and its implementation methods, which all fall within the scope of the present invention.

Claims (10)

1. The treatment method of the leaching solution of the waste lithium ion battery is characterized by comprising the following steps of: adding a complexing agent into the leaching solution of the waste lithium ion battery, and constructing an electrolytic tank with an electrolytic counter electrode; and alternately applying asymmetric forward voltage and reverse voltage to the electrolytic tank until the concentration of impurity metal ions in the leaching solution of the waste lithium ion battery reaches the expected value.

2. The method for treating a leaching solution of a waste lithium ion battery according to claim 1, wherein the complexing agent is at least one of EDTA and EDTA-2Na, STPP, H-501.

3. The method for treating waste lithium ion battery leaching liquid according to claim 1 or 2, wherein the ratio of the added molar amount of the complexing agent to the molar amount of the impurity metal ions is 0.3-1.2: 1.

4. The method for treating a leachate of a waste lithium ion battery according to claim 1, wherein the counter electrode is a modified carbon rod electrode or an inert electrode.

5. The method for treating a spent lithium ion battery leachate according to claim 4, wherein the inert electrode is a platinum electrode.

6. The method for treating waste lithium ion battery leaching liquid according to claim 1, wherein the forward voltage is 3-7 v; the reverse voltage is 6-14V.

7. The method for treating a spent lithium ion battery leachate of claim 1, wherein the forward voltage has a duration that is lower than a duration of the reverse voltage.

8. The method for treating a leaching solution of a waste lithium ion battery according to claim 7, wherein the duration of the forward voltage is 0.2 to 0.7ms, and the duration of the reverse voltage is 1 to 3ms.

9. The method for treating a spent lithium ion battery leachate according to claim 1, further comprising the steps of: introducing CO ₂ into the waste lithium ion battery leaching solution with the impurity metal ion concentration reaching the expected concentration, and then evaporating and concentrating to obtain the concentrated solution of lithium carbonate and complexing agent.

10. The method for treating a spent lithium ion battery leachate according to claim 9, wherein the concentrate containing the complexing agent is returned for recycling.