Method for synergistically reducing and recovering lithium carbonate from aluminum-containing waste power battery ternary positive electrode material

Abstract

The invention relates to a method for synergistically reducing and recovering lithium carbonate from an aluminum-containing waste power battery ternary positive electrode material. The method comprises the following steps: crushing the aluminum-containing ternary positive electrode material, and carrying out sufficient synergistic reduction under the condition that CO2 is introduced by taking aluminum impurities carried by the raw material as a reducing agent; and then carrying out water immersion under the condition of introducing CO2, and evaporating the water immersion liquid to dryness to obtain a lithium carbonate product. The water leaching residue can be used as a raw material of a ternary positive electrode material precursor after alkali leaching and aluminum removal. According to the method, the generation of lithium metaaluminate impurities is effectively inhibited by utilizing the synergistic reduction effect of aluminum and CO2, the subsequent deep impurity removal pressure is relieved, the recovery process cost can be effectively reduced, and the method has good economic benefits and application prospects.

Description

Technical Field

[0001] The invention relates to the field of valuable metal recovery, and in particular to a method for recovering lithium carbonate from ternary positive electrode materials of aluminum-containing waste power batteries through synergistic reduction. Background Art

[0002] Ternary power batteries occupy an important share of up to 35% in the new energy vehicle market due to their advantages such as high energy density, low self-discharge and high operating voltage. Generally speaking, such batteries will enter the retirement stage after 5 to 8 years of use. Retired batteries are rich in a variety of valuable elements such as nickel, cobalt, manganese, and lithium, so they have high recycling potential. It is particularly noteworthy that ternary positive electrode materials account for more than 40% of the total value of the battery, which makes the recycling of valuable metals in ternary positive electrode materials a current key task.

[0003] At present, the methods for recycling ternary positive electrode materials are roughly divided into pyrometallurgy and hydrometallurgy. However, the process that is generally recognized to have industrial prospects is to use a combined pyrometallurgical + hydrometallurgical treatment technology, specifically to decompose and reduce the raw materials at high temperatures, so that the high-priced nickel, cobalt, and manganese elements are reduced to a low-priced acid-soluble state, and then leached, and purified and separated by precipitation, extraction, and other means. The recovery and extraction of nickel, cobalt, and manganese elements are relatively mature, but due to the presence of impurity aluminum, during the high-temperature reduction process, the lithium and aluminum elements partially combine to form lithium aluminate, affecting the subsequent lithium recovery efficiency.

[0004] CN201910859941.3 discloses a method for recovering valuable metals from ternary positive electrode materials of waste power batteries, wherein the positive electrode materials are subjected to high-temperature hydrogen reduction treatment, and the lithium-rich solution after water leaching is precipitated to prepare lithium carbonate. After acid leaching of the leached residue, KMnO4 is added to precipitate MnO2. The separated cobalt-nickel solution is extracted to obtain a nickel-containing salt solution and a cobalt-containing salt solution.

[0005] CN202380011867.4 discloses a method for selectively extracting lithium from waste lithium-ion battery powder by aluminum-carbon synergistic reduction, wherein a mixed solid consisting of waste battery powder, carbon powder and aluminum powder is mixed with an alcohol substance and ball-milled; after drying, it is roasted and then carbonated and immersed in water to extract lithium.

[0006] CN202410780655.9 discloses a method for recovering valuable metals from aluminum-containing waste power battery ternary positive electrode materials, directly using aluminum as a reducing agent for reduction. Subsequently, alkaline leaching is directly performed to remove most of the aluminum and aluminum oxide generated by the reduction. After acid leaching, a mixed solution containing nickel, cobalt, manganese, lithium and aluminum is obtained. Then, precipitation, extraction, hydrolysis and precipitation are performed in sequence to obtain the separated target element compound.

[0007] Among the above methods, hydrogen as a reducing agent has low utilization rate, high energy consumption and great safety hazards. If aluminum is used directly as a reducing agent, it still needs deep impurity removal in the later stage. The use of aluminum-carbon synergistic reduction requires extremely high raw material ratio and mixing degree, and is difficult to apply in practice. Therefore, it is urgent to find a low-cost, high-efficiency and low-energy lithium-ion battery recycling process. Summary of the invention

[0008] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for recovering lithium carbonate from aluminum-containing waste power battery ternary positive electrode materials by synergistic reduction. The method uses the aluminum impurities in the raw materials as a reducing agent to efficiently synergistically reduce the ternary positive electrode materials in a CO2 atmosphere, thereby reducing the recovery cost; at the same time, it also provides a new idea for pre-treatment of aluminum removal.

[0009] To achieve this object, the present invention adopts the following technical solutions: Step 1: crushing the aluminum-containing ternary positive electrode material; Step 2: subjecting the raw materials described in step 1 to a fully coordinated reduction reaction under the condition of introducing CO2; Step 3: The reduced material described in step 2 is immersed in water under the condition of passing CO2 to obtain leaching residue and leaching liquid. The main elements of the leaching residue are Co, Ni, Mn, and Al. The leaching residue can be used as a raw material for the precursor of the ternary positive electrode material after aluminum removal by alkaline leaching. The main metal element in the leaching liquid is Li; Step 4: The aqueous extract described in step 3 is evaporated to dryness to obtain a lithium carbonate product.

[0010] The method provided by the present invention for recovering valuable metals from aluminum-containing waste power battery ternary positive electrode materials uses the aluminum impurities in the raw materials as a reducing agent, which can greatly reduce the cost of the recovery process. The reactions occurring during the reduction process are: 6LiNi 0.5 Co 0.2 Mn 0.3 O2+2Al→3Li2O+3NiO+1.2CoO+1.8MnO+Al2O3 Formula (1) Li2O+Al2O3→2LiAlO2 Formula (2) Li2O+CO2→Li2CO3 Formula (3) LiAlO2+CO2→Li2CO3+ Al2O3 Formula (4) During the reduction process, the continuous introduction of CO2 promotes the forward reaction of equation (4), thereby inhibiting the generation of LiAlO2. The reaction products are mainly metal oxides, lithium carbonate, aluminum oxide and some unreacted aluminum.

[0011] Subsequently, water immersion was carried out under the condition of introducing CO2, and the reaction that occurred was: Li2CO3+H2O+CO2→LiHCO3 formula (5) The low-solubility Li2CO3 is converted into the high-solubility LiHCO3 in the carbonated aqueous solution. The aqueous solution is then evaporated to dryness to obtain the lithium carbonate product.

[0012] The water leaching residue mainly contains metal oxides, alumina and some unreacted aluminum. The water leaching residue is alkali leached to remove most of the aluminum and alumina. After filtration, the phases in the residue are low-valent oxides of nickel, cobalt and manganese, which can be used as raw materials for the precursor of ternary positive electrode materials.

[0013] According to the present invention, the aluminum content of the raw material ranges from 10% to 30%; for example, it can be 10%, 14%, 18%, 22%, 26%, and 30% and specific point values ​​between the above values. Due to limited space and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0014] Preferably, the particle size of the raw material after crushing is 20μm~50μm; for example, it can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, and 50μm, as well as specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0015] According to the present invention, the coordinated reduction reaction temperature is 450~750 o C; for example, it can be 450 o C. 500 o C. 550 o C. 600 o C. 650 o C. 700 o C. and 750 o Due to space limitations and for the sake of brevity, the present invention will no longer exhaustively list C and specific point values ​​between the above-mentioned values.

[0016] According to the present invention, the reduction time is 2 to 4 hours; for example, it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours, as well as specific points between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0017] According to the present invention, the rate of introducing CO2 for synergistic reduction is 2 to 4 L / min; for example, it can be 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, and 4 L / min, as well as specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0018] According to the present invention, the water immersion temperature under the condition of introducing CO2 is 20~70 o C; for example, it can be 20 o C. 25 o C. 30 o C. 35 o C. 40 o C. 45 o C. 50 o C. 55 o C. 60 o C. 65 o C. and 70 o Due to space limitations and for the sake of brevity, the present invention will no longer exhaustively list C and specific point values ​​between the above-mentioned values.

[0019] According to the present invention, the rate of introducing CO2 through water immersion under the conditions of introducing CO2 is 2 to 4 L / min; for example, it can be 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, and 4 L / min, as well as specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them all.

[0020] According to the present invention, the liquid-to-solid ratio of water immersion under the condition of introducing CO2 is 10:1 ~ 20:1 mL / g; for example, it can be 10:1ml / g, 12:1ml / g, 14:1ml / g, 16:1ml / g, 18:1ml / g, and 20:1ml / g and specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them all.

[0021] According to the present invention, the water immersion time under the condition of introducing CO2 is 4 to 6 hours; for example, it can be 4 hours, 5 hours, and 6 hours, as well as specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them all.

[0022] According to the present invention, the stirring speed of alkali leaching of water-leached slag is 350-550 r / min; for example, it can be 350 r / min, 450 r / min, 550 r / min and specific points between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0023] According to the present invention, the stirring time of alkali leaching of water-leached slag is 2 to 4 hours; for example, it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours, as well as specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0024] According to the present invention, the alkali leaching liquid-solid ratio of the water-leached residue is 4:1~10:1 mL / g; for example, it can be 4:1 ml / g, 5:1 ml / g, 6:1 ml / g, 7:1 ml / g, 8:1 ml / g, 9:1 ml / g, and 10:1 ml / g, as well as specific point values ​​between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0025] According to the present invention, the alkali leaching temperature of the water leaching residue is 50~90 o C; for example, it can be 50 o C. 60 o C. 70 o C. 80 o C. and 90 o Due to space limitations and for the sake of brevity, the present invention will no longer exhaustively list C and specific point values ​​between the above-mentioned values.

[0026] Preferably, the alkaline leaching agent is sodium hydroxide solution.

[0027] Preferably, the concentration of the sodium hydroxide solution is 1-5 mol / L; for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, and 4 mol / L, as well as specific points between the above values. Due to space limitations and for the sake of simplicity, the present invention will no longer list them exhaustively.

[0028] Compared with the prior art solutions, the present invention has at least the following beneficial effects: The present invention utilizes aluminum impurities carried by raw materials as a reducing agent, and synergistically reduces them in a CO2 atmosphere, effectively inhibiting the generation of lithium aluminate impurities, reducing the pressure of subsequent deep impurity removal, and reducing the cost of the recovery process. In addition, the reduction reaction of aluminum impurities as a reducing agent itself releases a large amount of heat and is highly spontaneous, and does not need to be carried out in an ultra-high temperature environment, which can effectively save energy; (2) The whole operation process of the present invention is simple and the production cost is low. The overall recovery rates of nickel, cobalt, manganese and lithium can reach 99%, 98%, 99% and 95%, respectively, and the aluminum removal rate can reach 98%, which has good economic benefits and application prospects.

[0029] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, but these all belong to the protection scope of the present invention. Example 1

[0030] Step 1: crush the aluminum-containing ternary positive electrode material, the aluminum content in the raw material is 10%, and the particle size of the raw material after crushing is 20μm; Step 2: The raw materials described in step 1 are subjected to a sufficient coordinated reduction reaction under the condition of introducing CO2, and the coordinated reduction reaction temperature is 750 o C, reduction time is 4h, CO2 introduction rate is 4L / min; Step 3: Soak the reduced material in step 2 in water under the condition of passing CO2, and the water soaking temperature under the condition of passing CO2 is 20 o C, the rate of CO2 introduction is 2 L / min, the water leaching liquid-to-solid ratio is 10:1 mL / g, and the water leaching time is 4h. Water leaching residue and water leaching liquid are obtained. The main elements of the water leaching residue are Co, Ni, Mn, and Al. The water leaching residue can be used as the raw material of the precursor of the ternary positive electrode material after aluminum removal by alkaline leaching. The reagent used for alkaline leaching is sodium hydroxide solution with a concentration of 1 mol / L. The stirring speed of alkaline leaching is 350r / min, the stirring time is 4h, the liquid-to-solid ratio is 10:1mL / g, and the temperature is 90 o C. The recovery rates of Co, Ni and Mn are 99%, 97% and 97% respectively, and the removal rate of Al is 96%. The main metal element in the water leaching solution is Li; Step 4: The aqueous extract described in step 3 is evaporated to dryness to obtain a lithium carbonate product, and the Li recovery efficiency is 94%. Example 2

[0031] Step 1: crush the aluminum-containing ternary positive electrode material, the aluminum content in the raw material is 30%, and the particle size of the raw material after crushing is 50μm; Step 2: The raw materials described in step 1 are subjected to a sufficient coordinated reduction reaction under the condition of introducing CO2, and the coordinated reduction reaction temperature is 450 o C, reduction time is 2h, CO2 introduction rate is 2L / min; Step 3: Soak the reduced material in step 2 in water under the condition of passing CO2, and the water soaking temperature under the condition of passing CO2 is 70 o C, the rate of CO2 introduction is 4 L / min, the water leaching liquid-to-solid ratio is 20:1 mL / g, and the water leaching time is 6h. Water leaching residue and water leaching liquid are obtained. The main elements of the water leaching residue are Co, Ni, Mn, and Al. The water leaching residue can be used as the raw material of the precursor of the ternary positive electrode material after aluminum removal by alkaline leaching. The reagent used for alkaline leaching is sodium hydroxide solution with a concentration of 5 mol / L. The stirring speed of alkaline leaching is 550r / min, the stirring time is 2h, the liquid-to-solid ratio is 4:1mL / g, and the temperature is 50 o C. The recovery rates of Co, Ni and Mn are 99%, 98% and 99% respectively, and the removal rate of Al is 98%. The main metal element in the water leaching solution is Li; Step 4: The aqueous extract described in step 3 is evaporated to dryness to obtain a lithium carbonate product, and the Li recovery efficiency is 95%.

[0032] Comparative Example 1 Step 1: crush the aluminum-containing ternary positive electrode material, the aluminum content in the raw material is 30%, and the particle size of the raw material after crushing is 50μm; Step 2: The raw materials described in step 1 are subjected to a sufficient coordinated reduction reaction under the condition of introducing CO2, and the coordinated reduction reaction temperature is 450 o C, reduction time is 2 h, CO2 introduction rate is 0 L / min; Step 3: Soak the reduced material in step 2 in water under the condition of passing CO2, and the water soaking temperature under the condition of passing CO2 is 70 o C, the rate of CO2 introduction is 4 L / min, the water leaching liquid-to-solid ratio is 20:1 mL / g, and the water leaching time is 6h. Water leaching residue and water leaching liquid are obtained. The main elements of the water leaching residue are Co, Ni, Mn, and Al. The water leaching residue can be used as the raw material of the precursor of the ternary positive electrode material after aluminum removal by alkaline leaching. The reagent used for alkaline leaching is sodium hydroxide solution with a concentration of 5 mol / L. The stirring speed of alkaline leaching is 550r / min, the stirring time is 2h, the liquid-to-solid ratio is 4:1mL / g, and the temperature is 50 o C. The recovery rates of Co, Ni, and Mn were 86%, 94%, and 89%, respectively, and the removal rate of Al was 52%. The main metal element in the water leaching solution was Li; Step 4: The aqueous extract described in step 3 is evaporated to dryness to obtain a lithium carbonate product, and the Li recovery efficiency is 66%.

[0033] Comparative Example 2 Step 1: crush the aluminum-containing ternary positive electrode material, the aluminum content in the raw material is 30%, and the particle size of the raw material after crushing is 170μm; Step 2: The raw materials described in step 1 are subjected to a sufficient synergistic reduction reaction under the condition of introducing CO2, and the synergistic reduction reaction temperature is 450 o C, reduction time is 2h, CO2 introduction rate is 2L / min; Step 3: Soak the reduced material in step 2 in water under the condition of passing CO2, and the water soaking temperature under the condition of passing CO2 is 70 oC, the rate of CO2 introduction is 4 L / min, the water leaching liquid-to-solid ratio is 20:1 mL / g, and the water leaching time is 6h. Water leaching residue and water leaching liquid are obtained. The main elements of the water leaching residue are Co, Ni, Mn, and Al. The water leaching residue can be used as the raw material of the precursor of the ternary positive electrode material after aluminum removal by alkaline leaching. The reagent used for alkaline leaching is sodium hydroxide solution with a concentration of 5 mol / L. The stirring speed of alkaline leaching is 550r / min, the stirring time is 2h, the liquid-to-solid ratio is 4:1mL / g, and the temperature is 50 o C. The recovery rates of Co, Ni, and Mn are 90%, 88%, and 78%, respectively, and the removal rate of Al is 78%. The main metal element in the water leaching solution is Li; Step 4: The aqueous extract described in step 3 is evaporated to dryness to obtain a lithium carbonate product, and the Li recovery efficiency is 80%.

Claims

1. A method for recovering lithium carbonate from aluminum-containing waste power battery ternary positive electrode materials by synergistic reduction, characterized in that: The method is: Step 1: crushing the aluminum-containing ternary positive electrode material; Step 2: subjecting the raw materials described in step 1 to a fully coordinated reduction reaction under the condition of introducing CO2; Step 3: The reduced material described in step 2 is immersed in water under the condition of passing CO2 to obtain leaching residue and leaching liquid. The main elements of the leaching residue are Co, Ni, Mn, and Al. The leaching residue can be used as a raw material for the precursor of the ternary positive electrode material after aluminum removal by alkali leaching. The main metal element in the leaching liquid is Li. Step 4: The aqueous extract described in step 3 is evaporated to dryness to obtain a lithium carbonate product.

2. A method for recovering lithium carbonate by synergistic reduction from aluminum-containing waste power battery ternary positive electrode materials according to claim 1, characterized in that: In step 1, the aluminum content of the raw material is in the range of 10% to 30%; Preferably, the particle size of the raw material after crushing is 20 μm to 50 μm.

3. The method for recovering lithium carbonate by synergistic reduction from aluminum-containing waste power battery ternary positive electrode materials according to claim 1, characterized in that: In step 2, the coordinated reduction reaction temperature is 450-750 o C, the reduction time is 2 to 4 hours, and the rate of CO2 introduction is 2 to 4 L / min.

4. The method for recovering lithium carbonate by synergistic reduction from aluminum-containing waste power battery ternary positive electrode materials according to claim 1, characterized in that: In step 3, the water immersion temperature is 20-70°C under the condition of introducing CO2. o C, the rate of CO2 introduction is 2 ~ 4L / min, the water-liquid-solid ratio is 10:1 ~ 20:1 mL / g, and the water immersion time is 4~6 h.

5. The method for recovering lithium carbonate by synergistic reduction from aluminum-containing waste power battery ternary positive electrode materials according to claim 1, characterized in that: In step 3, the leached residue is alkali-leached to remove aluminum, the alkali leaching stirring speed is 350-550 r / min, the stirring time is 2-4 h, the liquid-solid ratio is 4:1-10:1 mL / g, the temperature is 50-90 o C; Preferably, the alkaline leaching agent is a sodium hydroxide solution; Preferably, the concentration of the sodium hydroxide solution is 1-5 mol / L.