A compound solvent for extracting lithium from waste lithium battery positive electrode material and application thereof

Abstract

The application discloses a kind of for extracting lithium of waste lithium battery positive electrode material complex solvent and application thereof.The complex solvent includes formic acid and accelerator, the accelerator is alcohol or ether substance;Wherein, accelerator is 20-50% by mass fraction.Mixing waste lithium battery positive electrode material with complex solvent and stirring, after reaction, centrifugal separation, the supernatant is dried to obtain lithium-containing solid product.The application uses alcohol or ether substance-formic acid complex solvent, utilizes the reaction capacity of formic acid and positive electrode material and the promotion capacity of alcohol or ether to this reaction, only needs to realize the separation of lithium and nickel cobalt manganese and other elements by one-step stirring, lithium recovery rate is high, the purity of obtained lithium product is high, no acid-containing wastewater is generated, green and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery recycling technology, specifically relating to a compound solvent for extracting lithium from the positive electrode material of waste lithium batteries and its application. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles and mobile electronic devices. With continued use, their charge / discharge performance gradually declines until they are no longer usable, typically lasting 3-5 years. Used lithium-ion batteries are considered hazardous waste and cannot be disposed of arbitrarily; they must undergo proper treatment. Furthermore, the cathode materials in lithium-ion batteries (such as LiFePO4, LiNiO2, and LiMn2O4) contain metallic lithium (Li), as do lithium nickel cobalt manganese oxide (ternary) batteries, giving them significant commercial value. In recent years, lithium iron phosphate and ternary materials have been the most widely used cathode materials in my country's lithium-ion batteries. With the price of metallic Li continuing to rise, the price of lithium carbonate even reached approximately 450,000 yuan / ton at one point. Therefore, recycling metallic Li from the cathode materials of used lithium-ion batteries is not only a way to reuse waste but also generates considerable economic benefits, making it of great significance.

[0003] Traditional methods for recycling waste cathode materials employ hydrometallurgy, using aqueous solutions of inorganic acids such as H2SO4, HCl, and HNO3 as leaching agents. The strong acidity of these inorganic acids dissolves the waste cathode materials, demonstrating a certain recovery efficiency. Leaching cathode materials from waste lithium-ion batteries with inorganic acids can recover over 99% of cobalt and lithium. However, this process uses high acid concentrations, which can corrode equipment and release SO3, HCl, and NO3. xThe leaching process generates toxic gaseous pollutants, and the waste acid after leaching is difficult to treat, posing potential hazards to human health and the environment. Therefore, traditional recycling methods are insufficient in terms of environmental friendliness and safety. Furthermore, the products obtained by traditional methods are mixtures of metal salts (lithium and cobalt salts), and the products are even more complex for ternary materials. Due to the low purity of the products, further purification with external precipitants is required. After leaching, the leachate contains a large number of valuable metal ions. Adding a suitable precipitant allows the valuable metals to be separated and recovered in the form of precipitation. Commonly added precipitants include NaOH, Na₂CO₃, H₂C₂O₄, and (NH₄)₂CO₃, which yield corresponding hydroxides, carbonates, oxalates, etc., of the valuable metals. It is evident that the traditional method has a complex process route and limited economic efficiency. In recent years, various organic acid systems with advantages such as recyclability, easy degradation, and environmental friendliness have been widely studied, mainly including organic acid-aqueous solutions and liquid organic acid-reducing agent solutions. However, the organic acid-aqueous solution system still suffers from problems such as acidic wastewater and the need to add hydrogen peroxide, and the leaching of lithium metal is not ideal. Compared with traditional methods, this system still has unresolved issues regarding its environmental friendliness and safety. Patent (CN201910943818) discloses a method for recycling cathode materials from waste ternary batteries using a mixture of oxalic acid and hydrogen peroxide, but it uses an oxalic acid solution for lithium extraction, which still generates acidic wastewater.

[0004] In summary, for the recycling of cathode materials from spent lithium batteries, there is an urgent need to develop novel anhydrous solvent systems with high lithium recovery rates and selectivity. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned technical problems by providing a compound solvent for extracting lithium from waste lithium-ion battery cathode materials and its application. This method uses an alcohol or ether-formic acid compound solvent, which is an anhydrous system. Utilizing the reactivity of formic acid with the cathode material and the promoting effect of the alcohol or ether on this reaction, lithium can be separated from other elements such as nickel, cobalt, and manganese through a single stirring step. The lithium recovery rate is high, the obtained lithium product is of high purity, and no acidic wastewater is generated, making it environmentally friendly.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A compound solvent for extracting lithium from waste lithium battery cathode materials is provided, comprising formic acid and an accelerator, wherein the accelerator is an alcohol or ether substance; wherein the accelerator accounts for 20-50% by mass percentage.

[0008] According to the above scheme, the compound solvent is prepared by mixing at a temperature of 20-100℃ for 0.5-2 hours.

[0009] According to the above scheme, the boiling point of the alcohol or ether substance is 80-160℃.

[0010] According to the above scheme, the alcohol is propanol (C3H8O) or butanol (C4H8O). 10 O), Pentanol (C5H) 12 O), hexanol (C6H) 14 At least one of (O); the ether is propyl ether (C6H) 14 O), butyl ether (C8H) 18 At least one of O), ethylene glycol methyl ether (C3H8O2), and ethylene glycol tert-butyl ether.

[0011] According to the above scheme, the cathode material of the waste lithium battery is LiFePO4, LiNiO2, LiMn2O4 or ternary material LiCo. x Mn y Ni 1-x-y O2.

[0012] An application of the above-mentioned compound solvent in extracting lithium from waste lithium battery cathode materials is provided.

[0013] A method for extracting lithium from waste lithium battery cathode materials is provided, using the aforementioned compound solvent. The specific steps are as follows:

[0014] The waste lithium battery cathode material is mixed and stirred with the compound solvent. After the reaction is completed, the mixture is centrifuged and the supernatant is dried to obtain a lithium-containing solid product.

[0015] According to the above scheme, the mass ratio of the waste lithium battery cathode material to the compound solvent is 0.005-0.02:1.

[0016] According to the above scheme, the stirring temperature is 50-90℃, the stirring time is 4-12h, and the stirring speed is 200-1000rpm.

[0017] According to the above scheme, the drying operation is carried out in an air atmosphere, the drying temperature is 100-200℃, and the drying time is within 3 hours.

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

[0019] 1. This invention provides an alcohol or ether-formic acid complex solvent with sufficient β-acidity; since the formic acid solvent needs to dissociate in water to release the acidic H+. +Pure formic acid itself has intermolecular hydrogen bonds, which occupy its active sites and make it difficult to fully exert its β-acid function. In this system, alcohols or ethers contain active oxygen sites, which can weaken the intermolecular interactions of formic acid, thereby exposing more formic acid active sites and enhancing the leaching reaction ability of formic acid with lithium in cathode materials. This can significantly improve the recovery rate of lithium extracted from waste cathode materials, and the resulting lithium product has high purity and has important industrial application value.

[0020] 2. In this invention, the lithium battery cathode material (such as ternary waste) is composed of multiple metallic elements (such as Li, Co, Ni, and Mn). When using pure formic acid, the lithium recovery rate is low due to the insufficient exposure of its active sites. If a traditional acidic eutectic solvent (such as formic acid-quaternary ammonium salt) is used, its excessively strong L-alkalinity causes other metals to be extracted simultaneously due to strong complexation, resulting in poor lithium selectivity and consequently, low purity of the lithium product. Furthermore, the presence of halide ions (such as Cl-) in the eutectic solvent... - The presence of [acid] makes it highly corrosive. The compound solvent system used in this invention has suitable β-acidity and L-basicity, and contains only C, H, and O elements, which can achieve efficient recovery of lithium elements while ensuring the purity of lithium products.

[0021] 3. This invention provides a method for using an alcohol or ether-formic acid compound solvent. The compound solvent is an anhydrous system, which avoids the problems of corrosion and acidic wastewater compared to acidic aqueous solutions. After mixing the compound solvent with the cathode material, a high-content lithium solution can be obtained with only one stirring operation. After drying, a lithium-containing solid product is obtained, showing high lithium recovery rate and selectivity. The operation is simple, the raw materials are cheap and readily available, the compound solvent can be recycled and reused, no waste liquid is generated, it is green and environmentally friendly, and the cost is low. Attached Figure Description

[0022] Figure 1 The process diagrams of Example 1 are shown, including a diagram of the system after stirring (a) and a diagram of the system after drying (b). Detailed Implementation

[0023] To enable those skilled in the art to fully understand the technical solution and beneficial effects of the present invention, the following description is provided in conjunction with the accompanying drawings and specific embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0024] Example 1

[0025] A method for extracting lithium from waste lithium battery cathode materials is provided, comprising the following steps:

[0026] 1) Mix n-propanol and formic acid at 40°C for 2 hours to prepare a compound solvent containing 20 wt% n-propanol.

[0027] 2) Add black powder of ternary cathode material waste (hereinafter referred to as ternary waste) to the compound solvent. The mass fractions of the four elements Li, Co, Ni and Mn are 6.8%, 6.3%, 40.7% and 2.7%, respectively. The mass ratio of ternary waste black powder to compound solvent is 0.02:1. Then stir the reaction at 60℃ for 10h and the stirring speed is 450rpm.

[0028] 3) After the reaction was completed, a clear liquid with a high lithium content was obtained by centrifugation. This liquid was then dried at 120°C for 1 hour in air to obtain a lithium-containing solid product. The physical appearance of the system after stirring and after drying is shown below. Figure 1 As shown.

[0029] Examples 2-9

[0030] The specific operation is the same as in Example 1, except that the specific type of positive electrode material (the same in Examples 1-8, all of which are ternary waste materials), the choice of alcohol or ether formulation, mixing conditions, reaction conditions and drying conditions are listed in the table below.

[0031] Table 1

[0032]

[0033] Comparative Example 1

[0034] Anhydrous formic acid was used as a solvent and added to the ternary waste material as in Example 1, with a mass ratio of ternary waste material to formic acid of 0.02:1. The reaction was carried out at 60°C for 10 hours with stirring at 450 rpm. After the reaction was completed, a clear lithium-containing liquid was obtained by centrifugation. This liquid was dried in air at 120°C for 1 hour to obtain a lithium-containing solid product.

[0035] Test methods for each embodiment:

[0036] Approximately 0.05 g of lithium-containing solid product was digested with 10 mL of concentrated nitric acid, diluted to 1000 mL (so that the nitric acid content was less than 2%), and the content of elements such as lithium, cobalt, nickel, and manganese in the product was obtained by measuring inductively coupled plasma mass spectrometry (ICP) and atomic absorption spectrometry (AAS).

[0037] The test results are shown in Table 2 below.

[0038] Table 2

[0039]

[0040]

[0041] Based on the analysis of the embodiments and their results in Tables 1 and 2, it can be seen that the compound solvent of the present invention exhibits good extraction effects on both ternary waste and lithium iron phosphate, with high lithium recovery rate and selectivity. Furthermore, the product purity produced using this compound solvent is at least 90.64%, and several embodiments achieve a purity of over 97%, indicating its significant effect on the selective separation of lithium. In addition, by comparing Examples 1-6 and Comparative Example 1, it can be found that the compound solvent has a significant advantage over pure formic acid in terms of lithium recovery rate and selectivity, indicating that the promoter (alcohol or ether) used in the compound solvent does indeed improve the lithium recovery effect.

[0042] It should be noted that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention. The method of the present invention is only a part of the implementation scheme and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for extracting lithium from waste lithium battery cathode materials, characterized in that, The specific steps are as follows: Waste lithium battery cathode material is mixed and stirred with a compound solvent. After the reaction is complete, the mixture is centrifuged, and the supernatant is dried to obtain a lithium-containing solid product; wherein: The compound solvent is formic acid and an accelerator, wherein the accelerator is an alcohol; and the accelerator accounts for 20-50% by mass percentage; the alcohol is at least one of propanol, butanol, pentanol or hexanol. The mass ratio of the waste lithium battery cathode material to the compound solvent is 0.005-0.02:1; The stirring temperature is 50-90℃, the stirring time is 4-12h, and the stirring speed is 200-1000rpm; The drying operation is carried out in an air atmosphere, with a drying temperature of 100-200℃ and a drying time of up to 3 hours. The compound solvent is prepared by mixing at 40-100℃ for 0.5-2 hours.

2. The method according to claim 1, characterized in that, The cathode material of the spent lithium batteries is LiFePO4, LiNiO2, LiMn2O4, or the ternary material LiCo. x Mn y Ni 1-x-y O2.

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