A method for integrated lithium extraction from NCM and LFP mixed waste lithium ion battery black powder

Abstract

The present application relates to the resource recycling technology field of waste lithium ion battery, in particular to a kind of NCM and LFP mixed waste lithium ion battery black powder integrated lithium extraction method.Step as follows: NCM waste lithium ion battery black powder is mixed with LFP waste lithium ion battery black powder, and mixed black powder is obtained;Mixed black powder is mixed with ternary eutectic molten salt and ball milled, and mixed material is obtained;Mixed material is heat treated under inert atmosphere, and heat treated product is obtained;Heat treated product is immersed in deionized water, solid-liquid separation is carried out, and lithium-containing solution and filter residue are obtained;Lithium-containing solution is added to precipitant, and refined lithium-containing solution is obtained by filtration;Refined lithium-containing solution is added to Na2CO3, and lithium precipitation reaction is carried out, and Li2CO3 is obtained by filtration, washing and drying;Ternary eutectic molten salt is NaCl-KCl-CaCl2 ternary eutectic molten salt or NaCl-KCl-MgCl2 ternary eutectic molten salt.The present application realizes the integrated efficient lithium extraction of NCM and LFP mixed black powder: without quality treatment, total lithium recovery rate is >90%, and the problem that existing technology cannot consider two kinds of positive electrode materials is solved.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery recycling technology, and in particular to an integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder. Background Technology

[0002] With the explosive growth of the new energy vehicle industry, the cumulative amount of retired lithium-ion batteries worldwide has exceeded ten million tons. Currently, multiple mainstream cathode materials exist in the market, including nickel-cobalt-manganese ternary (NCM) and lithium iron phosphate (LFP), resulting in a large amount of complex mixed battery black powder generated during recycling. Existing recycling technologies generally suffer from the problem of "good adaptability of single systems but low processing efficiency of mixed systems." Hydrometallurgical process: For the two types of cathode materials, NCM and LFP, completely different acidic or alkaline leaching systems need to be designed. When mixed, not only will a large amount of acid and alkali reagents be consumed, generating high-salt and high-COD wastewater, but the separation process of lithium ions and transition metal ions (Ni, Co, Mn, Fe, etc.) will be lengthy, and the recycling cost will increase significantly.

[0003] Pyrometallurgical processes typically require smelting at temperatures above 1400℃, resulting in extremely high energy consumption. Furthermore, lithium is easily lost by entering the slag phase, and the exhaust gas contains a large amount of harmful fumes, placing a heavy burden on the environment.

[0004] Eutectic molten salt recovery technology: As a novel recovery route that has emerged in recent years, this technology typically uses binary eutectic molten salts (such as NaCl-KCl) to treat battery black powder in air or an inert atmosphere, achieving selective lithium migration through the graphite intercalation cation exchange mechanism. However, the binary eutectic salt system is not ideal for lithium extraction from mixed cathode materials (especially those containing both NCM and LFP), mainly due to low lithium extraction rates and insufficient ability to disrupt the olivine structure of LFP, thus failing to effectively release the lithium.

[0005] Therefore, developing a novel eutectic molten salt system capable of simultaneously processing NCM and LFP mixed cathode materials to achieve an efficient, pre-sorting-free integrated lithium extraction process has become a pressing technical challenge in this field. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide an integrated lithium extraction method for NCM / LFP hybrid battery black powder, characterized by high lithium recovery rate, low salt cost, low energy consumption, and no need for separate processing. Through the synergistic design of a ternary molten salt system, efficient lithium migration from NCM and structural disruption of LFP are simultaneously achieved, solving the technical challenge of existing binary systems failing to simultaneously accommodate both cathode materials.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides an integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder, comprising the following steps: Mix NCM waste lithium-ion battery black powder with LFP waste lithium-ion battery black powder to obtain mixed black powder; The mixed black powder was mixed with ternary eutectic molten salt and then ball-milled to obtain a mixture. The mixture is heat-treated under an inert atmosphere to obtain a heat-treated product; The heat-treated product was added to deionized water for leaching, followed by solid-liquid separation to obtain a lithium-containing solution and filter residue. A precipitant was added to the lithium-containing solution, and the solution was filtered to obtain a purified lithium-containing solution. Na2CO3 was added to the purified lithium-containing solution to carry out a lithium precipitation reaction. The solution was then filtered, washed, and dried to obtain Li2CO3. The ternary eutectic molten salt is either NaCl-KCl-CaCl2 ternary eutectic molten salt or NaCl-KCl-MgCl2 ternary eutectic molten salt.

[0008] The synergistic lithium extraction mechanism of the ternary eutectic molten salt described in this invention is as follows: (1) K + Graphite intercalation-cation exchange effect: During heat treatment, Li is intercalated between graphite layers, and Li in the NCM lattice is transferred through ion exchange. + Driven to the molten salt phase, forming soluble lithium chloride, thus realizing the migration of lithium from the NCM lattice to the molten salt phase; (2) Ca 2+ / Mg 2+ Phosphate competitive coordination effect: Ca 2+ (or Mg) 2+ ) and PO4 3- Its affinity is far higher than Li + With PO4 3- The bonding strength, driven by thermodynamics, "steals" PO4 from LFP. 3- This disrupts its olivine structure and releases the bound Li. + ; (3) Low melting point and high mass transfer characteristics of molten salt medium: The ternary system of NaCl-KCl-CaCl2 and NaCl-KCl-MgCl2 has a melting point much lower than that of single salt and good fluidity. It forms a homogeneous liquid medium at 450~650℃, providing an efficient mass transfer environment for the two reactions mentioned above.

[0009] Through the above K + Ca 2+ / Mg 2+Through the functional division and synergistic effect, this invention enables the simultaneous completion of lithium migration in NCM and structural destruction in LFP in the same heat treatment step, thereby solving the technical problem that existing binary systems and single material systems cannot simultaneously achieve mixed cathode materials.

[0010] In a preferred embodiment of the present invention, the molar ratio of NaCl to KCl and CaCl2 in the NaCl-KCl-CaCl2 ternary eutectic molten salt is (38~42):(16~24):(38~42).

[0011] In a preferred embodiment of the present invention, the molar ratio of NaCl to KCl and MgCl2 in the NaCl-KCl-MgCl2 ternary eutectic molten salt is (30~40):(10~30):(40~50).

[0012] In a preferred embodiment of the present invention, the mass ratio of NCM waste lithium-ion battery black powder to LFP waste lithium-ion battery black powder is (9~1):(1~9).

[0013] In a preferred embodiment of the present invention, the mass ratio of the mixed black powder to the ternary eutectic molten salt is 1:(5~10).

[0014] In a preferred embodiment of the present invention, the conditions for the ball milling process are set as follows: ball-to-material ratio of 3:1 to 5:1, rotation speed of 300 to 600 rpm, and ball milling time of 20 to 60 min.

[0015] In a preferred embodiment of the present invention, the heat treatment conditions are set as follows: under an inert atmosphere, the temperature is increased to 450-650°C at a rate of 1-10°C / min, and held for 0.5-5 hours.

[0016] In a preferred embodiment of the present invention, the inert atmosphere is an argon atmosphere; the argon flow rate is 60~120mL / min, and the air in the furnace is replaced by argon gas for 3~5min before heating.

[0017] In a preferred embodiment of the present invention, the ratio of the heat treatment product to deionized water is 1g:(80~120)mL.

[0018] In a preferred embodiment of the present invention, the leaching temperature is 60~90℃ and the leaching time is 30~60min.

[0019] In a preferred embodiment of the present invention, the precipitant is Na2C2O4 and / or Na3PO4; the amount of precipitant added is 1 to 1.05 times the sum of the amounts of Ca and Mg in the eutectic salt; after adding the precipitant, precipitation is carried out at 60 to 90°C for 10 to 30 minutes, and the purified lithium-containing solution is obtained by filtration.

[0020] In a preferred embodiment of the present invention, the amount of Na2CO3 added is 0.5 to 0.6 times the amount of lithium in the purified lithium-containing solution; the conditions for the lithium precipitation reaction are set as follows: reaction at 100 to 120°C for 5 to 30 minutes.

[0021] Furthermore, the total content of positive electrode material in the hybrid battery black powder is about 70 wt%, and the graphite content is about 30 wt%.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) Achieve integrated and efficient lithium extraction from mixed black powder: Lithium can be extracted simultaneously in the same process without the need for separate pretreatment of NCM and LFP, with a total lithium recovery rate of over 90%, effectively overcoming the shortcomings of existing technologies that cannot take into account the recovery efficiency of two types of cathode materials.

[0023] (2) Wide process window and strong raw material adaptability: The mass ratio of NCM to LFP can be flexibly adjusted within the range of (9~1):(1~9), which effectively addresses the industrial problem of large fluctuations in the composition of waste battery black powder during actual recycling and has extremely strong industrial promotion value.

[0024] (3) Environmentally friendly and no corrosive wastewater is generated: Lithium can be separated by leaching with deionized water only, without the need for strong acids or alkalis, and no acidic / alkaline wastewater is generated. This is significantly different from traditional hydrometallurgical processes and greatly reduces wastewater treatment costs. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0031] The NCM532 black powder and LFP black powder used in this embodiment of the invention are obtained by discharging, dismantling, crushing, and sieving waste lithium-ion batteries. The main elemental composition of the NCM532 cathode material, by mass percentage, is Li (7.17%), Ni (31.54%), Co (12.49%), and Mn (17.48%); the main elemental composition of the LFP cathode material is Li (4.1%), Fe (34.5%), and P (19%). Both the NCM532 black powder and LFP black powder also contain approximately 30 wt% graphite.

[0032] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1: Treatment of NCM:LFP mixed black powder with a mass ratio of 1:1 using NaCl-KCl-CaCl2 system Take 1g of NCM532 black powder and 1g of LFP black powder and mix them evenly to obtain mixed black powder.

[0034] Weigh 20g of NaCl-KCl-CaCl2 ternary eutectic molten salt according to a salt-to-material ratio of 10:1, where the molar ratio of NaCl to KCl and CaCl2 is 40:20:40.

[0035] The mixed black powder and ternary eutectic molten salt were placed in a ball mill jar and ball milled at 500 rpm for 45 min using zirconia balls (5 mm) with a ball-to-material ratio of 3:1.

[0036] The ball-milled mixture was placed in a tube furnace and pre-purified with argon gas of ≥99.99% at a flow rate of 120 mL / min for 3 min. Then, the temperature was increased to 550℃ at a rate of 5℃ / min and held for 2 h.

[0037] The heat-treated product was added to deionized water at a liquid-to-solid ratio of 100 mL: 1 g, and leached at 60 °C for 60 min. After filtration, a lithium-containing solution and filter residue were obtained. ICP-OES analysis showed that the total lithium extraction rate was 93.1%.

[0038] Add 0.075 mol of Na2C2O4 to the lithium-containing solution, precipitate at 60℃ for 20 min, and filter to obtain a purified lithium-containing solution.

[0039] 0.0078 mol Na2CO3 was added to a purified lithium-containing solution, and the mixture was reacted and precipitated at 110 °C for 5 min. After filtration, washing, and drying, Li2CO3 (purity > 99%) was obtained.

[0040] Example 2: Treatment of NCM:LFP mixed black powder with a mass ratio of 1:1 using NaCl-KCl-MgCl2 system Take 1g of NCM532 black powder and 1g of LFP black powder and mix them evenly to obtain mixed black powder.

[0041] Weigh 16g of NaCl-KCl-MgCl2 ternary eutectic molten salt according to a salt-to-material ratio of 8:1, with the molar ratio of NaCl to KCl and MgCl2 being 30:30:40.

[0042] The mixed black powder and ternary eutectic molten salt were placed in a ball mill jar and ball milled at 600 rpm for 50 minutes using agate balls (3 mm) with a ball-to-material ratio of 5:1.

[0043] The ball-milled mixture was placed in a tube furnace and pre-purified with argon gas of ≥99.99% at a flow rate of 100 mL / min for 3 min. Then, the temperature was increased to 650℃ at a rate of 2℃ / min and held for 1 h.

[0044] The heat-treated product was added to deionized water at a liquid-to-solid ratio of 100 mL: 1 g, and leached at 80 °C for 40 min. After filtration, a lithium chloride solution and filter residue were obtained. ICP-OES analysis showed that the total lithium extraction rate was 91.7%.

[0045] Add 0.07 mol of Na2C2O4 to the lithium-containing solution, precipitate at 80℃ for 10 min, and filter to obtain a purified lithium-containing solution.

[0046] 0.0077 mol Na2CO3 was added to a purified lithium-containing solution, and the mixture was reacted and precipitated at 100℃ for 10 min. After filtration, washing and drying, Li2CO3 (purity > 99%) was obtained.

[0047] Comparative Example 1: Treatment of mixed black powder with a ternary system of NaCl-KCl-CaCl2 The only difference from Example 1 is that the molar ratio of the ternary eutectic molten salt NaCl to KCl and CaCl2 is replaced with 50:5:45.

[0048] ICP-OES analysis results: Total lithium extraction rate 78.6%. + The proportion decreased significantly while Ca 2+ The proportion increased slightly, while the total lithium extraction rate decreased from 93.1% to 78.6%. This indicates that K... + The graphite intercalation-cation exchange effect is the core driving force for lithium migration in NCMs, K + Insufficient Ca will severely weaken the effect, while excessive Ca will... 2+ Mass transfer efficiency may decrease due to increased molten salt viscosity.

[0049] Comparative Example 2: Treatment of mixed black powder with a NaCl-KCl-CaCl2 ternary system The only difference from Example 1 is that the salt-to-material ratio is 2:1.

[0050] ICP-OES analysis showed a total lithium extraction rate of 71.3%. This indicates that sufficient molten salt medium is necessary to ensure adequate dispersion of reactants, ion diffusion, and contact between the two phases. A salt-to-material ratio below 5:1 cannot provide sufficient reactive sites and mass transfer space.

[0051] Comparative Example 3: Treatment of Mixed Black Powder with NaCl-KCl Binary System The only difference from Example 1 is that the ternary eutectic molten salt is replaced with an equal mass of NaCl-KCl binary eutectic molten salt (the molar ratio of NaCl to KCl is 50:50). If Ca is unavailable... 2+ Due to the competitive coordination of phosphate groups, the olivine structure of LFP cannot be effectively disrupted, and lithium is firmly bound in the lattice, relying solely on K+ for coordination. + Exchange cannot achieve efficient lithium extraction from mixed systems.

[0052] ICP-OES analysis results: Total lithium extraction rate 48.6%.

[0053] Comparative Example 4: Treatment of Mixed Black Powder with NaCl-CaCl2 Binary System The only difference from Example 1 is that the ternary eutectic molten salt is replaced with an equal mass of NaCl-CaCl2 binary eutectic molten salt (the molar ratio of NaCl to CaCl2 is 50:50).

[0054] ICP-OES analysis results: Total lithium extraction rate 77.2%.

[0055] Comparative Example 5: Treatment of Mixed Black Powder with KCl-CaCl2 Binary System The only difference from Example 1 is that the ternary eutectic molten salt is replaced with an equal mass of KCl-CaCl2 binary eutectic molten salt (the molar ratio of KCl to CaCl2 is 50:50).

[0056] ICP-OES analysis results: Total lithium extraction rate 83.5%. Na was lacking. + Although the impact was relatively small, the synergistic effect of the entire ternary component was significantly better than that of any binary combination, confirming that Na + Its fundamental role in maintaining the low melting point and fluidity of molten salt.

[0057] Comparative Example 6: Treatment of Mixed Black Powder with NaCl-MgCl2 Binary System The only difference from Example 2 is that the ternary eutectic molten salt is replaced with an equal mass of NaCl-MgCl2 binary eutectic molten salt (the molar ratio of NaCl to MgCl2 is 50:50).

[0058] ICP-OES analysis results: Total lithium extraction rate 81.6%.

[0059] Comparative Example 7: Treatment of mixed black powder with a ternary system of NaCl-CaCl2-MgCl2 The only difference from Example 1 is that the ternary eutectic molten salt is replaced with an equal mass of NaCl-CaCl2-MgCl2 ternary eutectic molten salt (the molar ratio of NaCl to CaCl2 and MgCl2 is 40:20:40).

[0060] ICP-OES analysis results: Total lithium extraction rate 80.9%. Although two competing coordination cations are present, K is lacking. + This results in some lithium in the NCM not being effectively extracted, indicating that K + The function of K cannot be replaced by other cations; the core of this invention lies in K. + With Ca 2+ / Mg 2+ Division of labor and collaboration.

[0061] Comparative Example 8: Treatment of mixed black powder with a ternary system of NaCl-KCl-ZnCl2 The only difference from Example 1 is that the ternary eutectic molten salt is replaced with an equal mass of NaCl-KCl-ZnCl2 ternary eutectic molten salt (the molar ratio of NaCl to KCl and ZnCl2 is 40:20:40).

[0062] ICP-OES analysis results: Total lithium extraction rate 78.7%. Zn 2+ Its ability to damage LFP structures is less than that of Ca 2+ or Mg 2+ .

[0063] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder, characterized in that, Includes the following steps: Mix NCM waste lithium-ion battery black powder with LFP waste lithium-ion battery black powder to obtain mixed black powder; The mixed black powder was mixed with ternary eutectic molten salt and then ball-milled to obtain a mixture. The mixture is heat-treated under an inert atmosphere to obtain a heat-treated product; The heat-treated product was added to deionized water for leaching, followed by solid-liquid separation to obtain a lithium-containing solution and filter residue. A precipitant was added to the lithium-containing solution, and the solution was filtered to obtain a purified lithium-containing solution. Na2CO3 was added to the purified lithium-containing solution to carry out a lithium precipitation reaction. The solution was then filtered, washed, and dried to obtain Li2CO3. The ternary eutectic molten salt is either NaCl-KCl-CaCl2 ternary eutectic molten salt or NaCl-KCl-MgCl2 ternary eutectic molten salt.

2. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The molar ratio of NaCl to KCl and CaCl2 in the NaCl-KCl-CaCl2 ternary eutectic molten salt is (38~42):(16~24):(38~42).

3. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The molar ratio of NaCl to KCl and MgCl2 in the NaCl-KCl-MgCl2 ternary eutectic molten salt is (30~40):(10~30):(40~50).

4. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The mass ratio of NCM waste lithium-ion battery black powder to LFP waste lithium-ion battery black powder is (9~1):(1~9).

5. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The mass ratio of the mixed black powder to the ternary eutectic molten salt is 1:(5~10).

6. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The ball milling conditions are set as follows: ball-to-material ratio of 3:1 to 5:1, rotation speed of 300 to 600 rpm, and ball milling time of 20 to 60 min.

7. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The heat treatment conditions are set as follows: under an inert atmosphere, the temperature is increased to 450-650℃ at a rate of 1-10℃ / min, and held for 0.5-5h.

8. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The ratio of the heat-treated product to deionized water is 1g:(80~120)mL; the leaching temperature is 60~90℃, and the leaching time is 30~60min.

9. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The precipitant is Na2C2O4 and / or Na3PO4; the amount of precipitant added is 1 to 1.05 times the sum of the amounts of Ca and Mg in the eutectic salt; after adding the precipitant, precipitation is carried out at 60 to 90°C for 10 to 30 minutes, and the purified lithium-containing solution is obtained by filtration.

10. The integrated lithium extraction method for mixed NCM and LFP waste lithium-ion battery black powder according to claim 1, characterized in that, The amount of Na2CO3 added is 0.5 to 0.6 times the amount of lithium in the purified lithium-containing solution; the conditions for the lithium precipitation reaction are set as follows: react at 100 to 120°C for 5 to 30 minutes.