Method for selectively recovering nickel, cobalt and lithium from retired ternary lithium battery cathode material

Abstract

The application discloses a method for selectively recovering nickel, cobalt and lithium in positive electrode materials of retired ternary lithium batteries, and belongs to the technical field of resource recycling of retired lithium ion batteries and hydrometallurgy. The method uses a composite leaching system composed of ammonia, ammonium bicarbonate and sodium sulfite to selectively leach the positive electrode materials of the retired ternary lithium ion batteries, and obtains a leaching solution containing nickel, cobalt and lithium and a leaching residue through solid-liquid separation after the reaction. Under the optimal conditions, the leaching temperature is 80 DEG C, the concentration of Na2SO3 is 1.5 mol / L, the concentration of NH3H2O is 3 mol / L, the concentration of NH4HCO3 is 4 mol / L, the solid-liquid ratio is 100 g / L, and the leaching time is 100 min. Under the conditions, the leaching rates of Ni, Co and Li are 92.44%, 97.50% and 97.84% respectively, and the leaching rate of Mn is only 0.40%. The method can realize efficient leaching of Ni, Co and Li in the positive electrode materials of the retired ternary lithium ion batteries, reduce the co-leaching of impurity ions, and make Mn mainly remain in the leaching residue, so that the selective extraction of target valuable metals is realized. The method has the advantages of clear process conditions, good leaching selectivity and strong applicability.

Description

Technical Field

[0001] This invention relates to the field of retired lithium-ion battery resource recycling technology, specifically to a selective ammonia leaching method for recovering nickel, cobalt, and lithium from the cathode material of retired ternary lithium-ion batteries, and more particularly to a method for efficiently extracting the target valuable metals using an ammonia-ammonium bicarbonate-sodium sulfite composite system, applicable to the efficient and green recycling of cathode materials from retired ternary lithium-ion batteries. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and the energy storage industry, the use of lithium-ion batteries, especially ternary lithium-ion batteries, continues to increase. Correspondingly, the number of retired lithium-ion batteries is also rising. The cathode materials of retired ternary lithium-ion batteries contain high levels of valuable elements such as Ni, Co, Mn, and Li, possessing significant resource recycling value. Failure to effectively recycle them will not only waste strategic metal resources but also pose environmental pollution risks due to the release of heavy metals and electrolyte residues from the batteries.

[0003] Currently, the main methods for recovering valuable metals from retired lithium-ion batteries fall into two categories: pyrometallurgy and hydrometallurgy. While pyrometallurgy offers advantages such as large processing capacity and strong adaptability to raw material fluctuations, it typically suffers from high energy consumption, significant pollution control challenges, and limited efficiency in the comprehensive recovery of multiple metals. In contrast, hydrometallurgy, with its higher metal recovery rate, stronger process controllability, and greater ability to selectively separate multiple elements, has become one of the important technological routes for the resource utilization of retired lithium-ion batteries.

[0004] In hydrometallurgical recycling, leaching is a crucial step for releasing valuable metals and subsequent separation and purification. Depending on the leaching medium, common methods include acid leaching, ammonia leaching, and bioleaching. Acid leaching and ammonia leaching are widely used in the recycling of cathode materials from retired ternary lithium-ion batteries. While acid leaching generally offers high efficiency, it also has significant drawbacks. First, it consumes a large amount of acid, easily leading to equipment corrosion and increasing the cost of subsequent neutralization treatment. Second, under acidic conditions, impurity elements such as Al, Fe, Mg, and Ca, in addition to the target metal, can easily enter the liquid phase simultaneously, complicating subsequent impurity removal, extraction, and precipitation steps. Furthermore, Ni and Co have similar physicochemical properties, and their efficient separation typically requires multi-stage operations, increasing process length and operating costs.

[0005] The ammonia leaching system offers certain selectivity advantages. Under ammonia leaching conditions, Ni and Co can form relatively stable complexes with NH3, thus preferentially entering the solution, while Mn tends to exist as a poorly soluble solid phase in carbonate and weakly alkaline environments. Therefore, the reducing ammonia leaching method has the potential to reduce the proportion of impurity elements and non-target elements entering the liquid phase from the source, reducing the burden on subsequent separation and purification. Furthermore, compared with various alkaline regeneration processes, the ammonia leaching system also has potential advantages in process integration.

[0006] However, existing ammonia leaching methods still have several problems. First, for high-valence Ni and Co in the cathode materials of retired ternary lithium-ion batteries, without the introduction of suitable reducing components, the target metals are difficult to efficiently enter the liquid phase, resulting in low leaching rates. Second, the ammonia concentration in the system is not necessarily better the higher it is; excessively high ammonia content will increase volatilization losses and process control difficulties. Third, different combinations of ammonium salts and reducing agents have a significant impact on the leaching efficiency of the target metals and the selectivity of the system. Current technology still lacks a leaching system that can achieve efficient leaching of Ni, Co, and Li, significantly reduce the co-leaching of impurity ions, and ensure that Mn is mainly retained in the leaching residue.

[0007] Therefore, there is an urgent need to provide a selective ammonia leaching method with a reasonable leaching system composition, good selectivity, clear process conditions, and the ability to efficiently extract nickel, cobalt, and lithium from the cathode materials of retired ternary lithium-ion batteries. Summary of the Invention

[0008] The purpose of this invention is to provide a method for the selective recovery of nickel, cobalt, and lithium, cathode materials from retired ternary lithium batteries. This method utilizes a composite leaching system of ammonia, ammonium bicarbonate, and sodium sulfite to achieve efficient leaching of Ni, Co, and Li under relatively mild conditions, while reducing the co-leaching of impurity ions and ensuring that Mn is primarily retained in the leaching residue, thus balancing recovery efficiency and system selectivity.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This invention provides a method for the selective recycling of nickel-cobalt-lithium cathode materials from retired ternary lithium batteries, comprising the following steps:

[0011] Using retired ternary lithium-ion battery cathode materials as raw materials, a reducing ammonia leaching system composed of ammonia, ammonium bicarbonate, and sodium sulfite was employed for leaching. After the reaction, solid-liquid separation was performed to obtain a leachate containing nickel, cobalt, and lithium, as well as a leaching residue.

[0012] Sodium sulfite is used to promote the reduction leaching of nickel and cobalt; ammonia is used to form stable ammonia complexes with nickel and cobalt ions, promoting their entry into the liquid phase; ammonium bicarbonate is used to maintain the stability of the leaching system and promote the retention of manganese in the slag phase.

[0013] Preferably, the retired ternary lithium-ion battery cathode material comprises, by mass percentage: Ni 42.85%, Co 6.211%, Mn 10.71%, Li 7.872%, Al 0.7335%, Cu 0.51%, Ca 0.1381%, Fe 0.026%, Mg 0.312%, Zn 0.084%, and graphite and other insoluble impurities 4.63%.

[0014] Preferably, the process parameters are optimized in the following order: leaching temperature, sodium sulfite concentration, ammonia concentration, ammonium bicarbonate concentration, solid-liquid ratio, and leaching time.

[0015] More preferably, the preferred process conditions are: leaching temperature 80 ℃, sodium sulfite concentration 1.5 mol / L, ammonia concentration 3 mol / L, ammonium bicarbonate concentration 4 mol / L, solid-liquid ratio 100 g / L, and leaching time 100 min.

[0016] More preferably, under the above conditions, the leaching rates of Ni, Co and Li reach 92.44%, 97.50% and 97.84%, respectively, and the leaching rate of Mn is 0.40%.

[0017] Preferably, during the leaching process, high-valence Ni and Co are converted to low-valence states under the action of Na2SO3 and form stable complexes with NH3 to enter the liquid phase; Li dissociates along with the cathode material structure and enters the liquid phase; while Mn is mainly retained in the leaching residue in the form of a sparingly soluble solid phase.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention adopts the NH3·H2O-NH4HCO3-Na2SO3 composite leaching system, which can achieve efficient leaching of Ni, Co and Li under relatively mild conditions, while reducing the co-leaching of impurity ions and making Mn mainly enriched in the leaching residue, thus having good selectivity;

[0020] (2) By introducing Na2SO3 as a reducing agent, this invention can promote the conversion of high-valence Ni and Co to low-valence states, thereby strengthening their complexation leaching process in the ammonia leaching system and improving the extraction efficiency of the target metal.

[0021] (3) The process flow is relatively short, which facilitates the connection with the subsequent co-precipitation regeneration process of ternary materials;

[0022] (4) The process conditions of this invention are clear and the raw materials are readily available. It is suitable for selective ammonia leaching extraction of nickel, cobalt and lithium in the cathode materials of retired ternary lithium-ion batteries and has good application potential. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, wherein:

[0024] Figure 1 A graph showing pH changes in different leaching systems;

[0025] Figure 2 A comparison chart of leaching rates of Ni, Co, Mn, and Li under different reducing agent conditions;

[0026] Figure 3 The graph shows the effect of leaching temperature on the leaching efficiency of Ni, Co, Mn and Li.

[0027] Figure 4 The graph shows the effect of Na2SO3 concentration on the leaching efficiency of Ni, Co, Mn and Li.

[0028] Figure 5 The graph shows the effect of NH3·H2O concentration on the leaching efficiency of Ni, Co, Mn and Li.

[0029] Figure 6 The graph shows the effect of NH4HCO3 concentration on the leaching efficiency of Ni, Co, Mn and Li.

[0030] Figure 7 The graph shows the effect of the solid-liquid ratio on the leaching efficiency of Ni, Co, Mn, and Li.

[0031] Figure 8 The graph shows the effect of leaching time on the leaching efficiency of Ni, Co, Mn and Li.

[0032] Figure 9 XRD pattern of the leaching residue;

[0033] Figure 10 XPS spectra of the leaching residue. Detailed Implementation

[0034] The concept and technical effects of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0035] Example 1: Establishment of Leaching System and Screening of Reducing Agent

[0036] To determine an ammonia leaching system suitable for the selective extraction of valuable metals from cathode materials of retired ternary lithium-ion batteries, the pH values ​​of the ammonia water system and the ammonia water-ammonium bicarbonate system were first compared. Figure 1As shown in the figure. The results indicate that when ammonia is used alone as the leaching agent, the system pH is too high, which is not conducive to the selective leaching of Ni and Co. After adding ammonium bicarbonate, the system pH can be adjusted to a more suitable weakly alkaline range, which is conducive to the complexation leaching of Ni and Co and reduces the tendency of some impurities or non-target elements to enter the liquid phase. Therefore, NH3·H2O-NH4HCO3 was determined to be the basic leaching system.

[0037] Based on this, to improve the leaching efficiency of high-valence Ni and Co, sodium thiosulfate, sodium sulfite, and ammonium sulfite were selected as reducing agents for comparative experiments, such as... Figure 2 As shown in the figure. The results indicate that the leaching rates of Ni and Co were significantly improved after the addition of the reducing agent. The leaching effect of Ni and Co was best under sodium sulfite conditions, while Li maintained a relatively high leaching level, and the leaching rate of Mn remained at a low level. This demonstrates that sodium sulfite can improve the leaching rate of the target metal while maintaining good selectivity of the system. Therefore, NH3·H2O-NH4HCO3-Na2SO3 was selected as the selective leaching system of this invention.

[0038] Example 2: Optimal leaching conditions and leaching results

[0039] Based on the optimization results of Example 2, the leaching temperature, Na2SO3 concentration, NH3·H2O concentration, NH4HCO3 concentration, solid-liquid ratio, and leaching time were further optimized. The optimal leaching conditions were finally determined to be: leaching temperature 80 ℃, Na2SO3 concentration 1.5 mol / L, NH3·H2O concentration 3 mol / L, NH4HCO3 concentration 4 mol / L, solid-liquid ratio 100 g / L, and leaching time 100 min. Figures 3-8 As shown.

[0040] Leaching experiments were conducted under the above conditions, and the results showed that the leaching rates of Ni, Co, and Li were 92.44%, 97.50%, and 97.84%, respectively, while the leaching rate of Mn was only 0.40%. This demonstrates that the method of the present invention can achieve efficient leaching of Ni, Co, and Li, while reducing the co-leaching of impurity ions and ensuring that Mn is mainly retained in the leaching residue, exhibiting good selective leaching performance.

[0041] Example 3: Leaching Mechanism and Leaching Residue Analysis

[0042] To further elucidate the migration patterns of various metal elements in the method of this invention, the composition of the leachate and the leaching residue were characterized and analyzed. The composition of the leachate is shown in Table 1, and the XRD pattern of the leaching residue is shown in Table 1. Figure 9 As shown, XPS Figure 10As shown in the figure. The results indicate that the method of this invention mainly involves three types of reactions: reduction, complexation, and precipitation. High-valence Ni and Co are converted to low-valence states under the action of Na₂SO₃ and form stable complexes with NH₃, entering the liquid phase. Li is released into the liquid phase as the cathode material structure is destroyed. Mn, due to its weak complexation ability with NH₃ and its tendency to form insoluble solid phases in carbonate systems, is mainly retained in the leaching residue. These results demonstrate that the selective leaching of the method of this invention originates from the differences in the behavior of different elements during the reduction-complexation-precipitation process.

[0043] Table 1. Elemental composition and content of leachate

[0044] element Ni Co Mn Li Al Ca Mg Content (g / L) 39.61 6.06 0.043 7.702 0.089 0.0624 0.1075

Claims

1. A method for selectively recycling nickel-cobalt-lithium cathode materials from retired ternary lithium batteries, characterized in that, The cathode material of retired ternary lithium-ion batteries was brought into contact with a leaching system composed of NH3·H2O, NH4HCO3, Na2SO3 and water. The leaching reaction was carried out under stirring conditions. After the reaction was completed, solid-liquid separation was performed to obtain a leaching solution containing nickel, cobalt and lithium and a manganese-rich leaching residue.

2. The recycling method according to claim 1, characterized in that, The retired ternary lithium-ion battery cathode material undergoes one or more pretreatment steps, including discharge, disassembly, crushing, heat treatment, grinding, and sieving, before leaching, to obtain cathode active material enriched powder.

3. The recycling method according to claim 1, characterized in that, The concentration of NH3·H2O in the leaching system is 2.0–4.0 mol / L.

4. The recycling method according to claim 1, characterized in that, The concentration of NH4HCO3 in the leaching system is 3.0–5.0 mol / L.

5. The recycling method according to claim 1, characterized in that, The concentration of Na2SO3 in the leaching system is 1.0–2.0 mol / L.

6. The recycling method according to claim 1, characterized in that, The leaching temperature is 70–90 °C.

7. The recycling method according to claim 1, characterized in that, The solid-liquid ratio is 60–140 g / L.

8. The recycling method according to claim 1, characterized in that, The leaching time is 70–110 min.

9. The recycling method according to claim 1, characterized in that, During the leaching process, high-valence Ni and Co are converted to low-valence states under the action of Na2SO3 and form stable complexes with NH3 to enter the liquid phase; Li dissociates along with the cathode material structure and enters the liquid phase; Mn is retained in the leaching residue as a sparingly soluble solid phase.

10. The recycling method according to claim 1, characterized in that, The preferred leaching conditions are: leaching temperature 80 ℃, Na2SO3 concentration 1.5 mol / L, NH3·H2O concentration 3 mol / L, NH4HCO3 concentration 4 mol / L, solid-liquid ratio 100 g / L, and leaching time 100 min.

11. The recycling method according to claim 10, characterized in that, Under the preferred leaching conditions, the leaching rates of Ni, Co, and Li were 92.44%, 97.50%, and 97.84%, respectively, and the leaching rate of Mn was 0.40%.

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