A method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light

Abstract

The present invention discloses a method for extracting lithium from lithium iron phosphate batteries by photocatalysis under ultraviolet light, and belongs to the technical field of lithium battery recovery. The method comprises the following steps: adding waste lithium iron phosphate battery positive electrode powder and a photocatalyst to an extracting solution, sealing, photocatalyzing under ultraviolet light, and separating the precipitate and the solution after the irradiation to obtain a lithium-containing solution. The present invention utilizes ultraviolet light irradiation conditions for photocatalysis, so that the primary extraction rate of lithium elements in the waste lithium iron phosphate battery positive electrode powder reaches more than 60%, the operation is convenient, there is no secondary pollution to the environment, and the metal recovery rate is high.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery recycling, and in particular relates to a method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light. Background Art

[0002] As the global demand for renewable energy continues to grow, lithium batteries are becoming increasingly important as an efficient and environmentally friendly way of storing energy. The extraction process of lithium resources is usually energy-intensive and has a great impact on the environment. With the expansion of the new energy vehicle market and technological advancement, the demand for lithium batteries is expected to continue to rise. However, the service life of lithium batteries is usually 3 to 5 years. Studies have shown that if a large number of retired lithium batteries are not properly disposed of, the heavy metals and harmful chemical components contained in them will cause serious environmental damage and cause a waste of precious strategic metal resources. Therefore, the recycling and reuse of waste lithium batteries will also become one of the focuses of the industry, and the development of an efficient and environmentally friendly lithium extraction technology has become a research hotspot.

[0003] At present, waste lithium iron phosphate battery powder is mainly recycled through wet treatment, which is mainly divided into two categories: full leaching and selective leaching. Full leaching refers to leaching as many elements in the battery powder as possible into the solution without selection, but due to the large number of elemental components in the leaching solution, further separation and purification are required to obtain the required elements. Selective leaching is to select a suitable leaching agent to leach the required elements directly into the leaching solution, eliminating the subsequent separation and purification steps. Regarding selective extraction, most of the current research on the recycling of waste lithium iron phosphate batteries uses different leaching agents with high selectivity for lithium, and there is currently no related research on photocatalytic extraction of lithium.

[0004] Although some studies have proposed the use of photocatalysis to selectively extract precious metals from waste three-way catalytic converters and uranium from seawater, lithium, as a more active metal, has low activity and poor stability in photocatalytic reactions and is difficult to extract. Therefore, how to provide a method for efficient photocatalytic extraction of lithium is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the above technical problems, the present invention proposes a method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for extracting lithium from a lithium iron phosphate battery by photocatalysis under ultraviolet light comprises the following steps: adding waste lithium iron phosphate battery cathode powder and a photocatalyst into an extracting solution, sealing the solution, performing photocatalysis under ultraviolet light, and separating a precipitate and a solution after irradiation to obtain a lithium-containing solution.

[0008] Furthermore, the mass ratio of the waste lithium iron phosphate battery positive electrode powder to the photocatalyst is 1:(0.1-1).

[0009] Furthermore, the photocatalyst is titanium dioxide.

[0010] Furthermore, the extract is an ionic liquid.

[0011] Furthermore, the ionic liquid is an ammonium fluoride solution with a concentration of 1-10M.

[0012] Furthermore, the photocatalytic conditions are: temperature 20-30°C, working current 13-20A, light power density 1200-2100mW / cm 2 , photocatalytic time 1-24h.

[0013] Furthermore, the reactor is subjected to cooling circulation treatment during the photocatalytic process.

[0014] Reaction principle of the present invention: Photocatalytic extraction of lithium elements from waste lithium iron phosphate batteries utilizes the characteristics of photocatalysts that can generate photogenerated electrons and holes under light conditions. These photogenerated electrons and holes have strong reducing and oxidizing properties. When the photocatalyst is excited by photons with energy greater than or equal to its band gap, the electrons in the valence band will be excited to the conduction band, and the same number of holes will be left in the valence band. These photogenerated electrons and holes can undergo redox reactions with adsorbed substances on the surface of the photocatalyst. That is, under ultraviolet light irradiation, electrons react with oxygen to generate superoxide radicals, and holes react with water molecules in the solution to generate hydroxyl radicals. These free radicals have strong oxidizing properties and can oxidize divalent iron ions to trivalent iron ions, and lithium ions are released into the solution; in addition, holes in the valence band also have strong oxidizing properties and can directly participate in the oxidation reaction of divalent iron ions. The dominant position of these two reaction paths is affected by factors such as reaction conditions and redox potential. In view of the weak electron-withdrawing ability of lithium and based on considerations of the rate and selectivity of the photocatalytic reaction, an extracting solution needs to be added as a reaction medium to dissolve the metal elements. The present invention selects ammonium fluoride ion solution as the extracting solution.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects:

[0016] The present invention adds waste lithium iron phosphate battery positive electrode powder and photocatalyst into an extracting solution and irradiates the solution under ultraviolet light for a period of time, so as to more conveniently extract lithium elements from the lithium iron phosphate battery powder. The method has the advantages of simple operation, low cost, high recovery rate and less environmental pollution.

[0017] The present invention uses ultraviolet light irradiation conditions to carry out photocatalysis, so that the lithium element in the positive electrode powder of waste lithium iron phosphate batteries can be extracted at a rate of more than 60% at one time. The operation is convenient, there is no secondary pollution to the environment, and the metal recovery rate is high. In addition, for the catalyst particles suspended in the liquid, a centrifuge can be used to separate them, and the remaining residue can be dried and then the remaining metal can be recovered by physical or chemical methods. Not only does it improve economic benefits, but it also reduces resource waste and environmental pollution. DETAILED DESCRIPTION

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0020] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0021] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0022] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0023] The embodiment of the present invention discloses a method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light, comprising the following steps: adding waste lithium iron phosphate battery cathode powder and a photocatalyst into an extracting solution, sealing, photocatalyzing under ultraviolet light, and separating a precipitate and a solution after irradiation to obtain a lithium-containing solution. The extracting solution is used as a reaction medium to dissolve metal elements.

[0024] In the following preferred embodiments of the present invention, the mass ratio of the waste lithium iron phosphate battery positive electrode powder to the photocatalyst is 1: (0.1-1). The photocatalyst is titanium dioxide.

[0025] In the following preferred embodiments of the present invention, the extracting solution is an ionic liquid, which is an ammonium fluoride solution with a concentration of 1-10M, preferably 2-3M.

[0026] In the following preferred embodiments of the present invention, the photocatalytic conditions are: temperature 20-30°C, working current 13-20A, light power density 1200-2100mW / cm 2 The photocatalytic time is 1-24h, the light source is PLS-SXE300 / 300UV xenon light source with filter, and the constant temperature and constant speed magnetic stirrer is set to 400-500rpm to make the reactants fully contact. During the photocatalytic process, the reactor is cooled and circulated to prevent the container from cracking due to overheating. Specifically, a double-layer jacketed beaker is used as the reaction container, and circulating water is used for cooling in a bottom-in and top-out manner.

[0027] The raw materials used in the present invention are all purchased from the market.

[0028] The technical solution of the present invention is further illustrated by the following embodiments.

[0029] Example 1

[0030] A method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light, comprising the following steps:

[0031] (1) Weigh 0.1g of waste lithium iron phosphate battery positive electrode powder and 0.05g of titanium dioxide;

[0032] (2) Prepare 50 mL of 2M ammonium fluoride aqueous solution, add the waste lithium iron phosphate battery positive electrode powder and titanium dioxide into the ammonium fluoride aqueous solution, and seal;

[0033] (3) Photocatalysis was carried out at 25°C, the UV light source had an operating current of 17.5A, and the light power density was 1706.25mW / cm 2 The reaction light source uses PLS-SXE300 / 300UV xenon lamp light source with filter, and the constant temperature and constant speed magnetic stirrer is set at 400rpm to ensure full contact of the reactants;

[0034] (4) After irradiation for 8 hours, the precipitate is separated from the solution to obtain a solution containing lithium ions.

[0035] Example 2

[0036] A method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light, comprising the following steps:

[0037] (1) Weigh 0.1g of waste lithium iron phosphate battery positive electrode powder and 0.05g of titanium dioxide;

[0038] (2) Prepare 80 mL of 3M ammonium fluoride aqueous solution, add the waste lithium iron phosphate battery positive electrode powder and titanium dioxide into the ammonium fluoride aqueous solution, and seal;

[0039] (3) Photocatalysis was carried out at 25°C, the UV light source had an operating current of 17.5A, and the light power density was 1706.25mW / cm 2 The reaction light source uses PLS-SXE300 / 300UV xenon lamp light source with filter, and the constant temperature and constant speed magnetic stirrer is set at 400rpm to ensure full contact of the reactants;

[0040] (4) After irradiation for 12 hours, the precipitate is separated from the solution to obtain a solution containing lithium ions.

[0041] Example 3

[0042] A method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light, comprising the following steps:

[0043] (1) Weigh 0.2 g of waste lithium iron phosphate battery positive electrode powder and 0.105 g of titanium dioxide;

[0044] (2) Prepare 80 mL of 3M ammonium fluoride aqueous solution, add the waste lithium iron phosphate battery positive electrode powder and titanium dioxide into the ammonium fluoride aqueous solution, and seal;

[0045] (3) Photocatalysis was carried out at 26°C, the UV light source had an operating current of 19A, and the light power density was 1875mW / cm 2 The reaction light source uses PLS-SXE300 / 300UV xenon lamp light source with filter, and the constant temperature and constant speed magnetic stirrer is set at 500rpm to ensure full contact of the reactants;

[0046] (4) After irradiation for 11 hours, the precipitate is separated from the solution to obtain a solution containing lithium ions.

[0047] Example 4

[0048] A method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light, comprising the following steps:

[0049] (1) Weigh 0.1g of waste lithium iron phosphate battery positive electrode powder and 0.038g of titanium dioxide;

[0050] (2) Prepare 50 mL of 4M ammonium fluoride aqueous solution, add the waste lithium iron phosphate battery positive electrode powder and titanium dioxide into the ammonium fluoride aqueous solution, and seal;

[0051] (3) Photocatalysis was carried out at 25.5°C, the UV light source had an operating current of 18A, and the light power density was 1762.5mW / cm 2 The reaction light source uses PLS-SXE300 / 300UV xenon lamp light source with filter, and the constant temperature and constant speed magnetic stirrer is set at 450rpm to ensure full contact of reactants;

[0052] (4) After irradiation for 10 hours, the precipitate is separated from the solution to obtain a solution containing lithium ions.

[0053] Example 5

[0054] A method for photocatalytically extracting lithium from a lithium iron phosphate battery under ultraviolet light, comprising the following steps:

[0055] (1) Weigh 0.21 g of waste lithium iron phosphate battery positive electrode powder and 0.12 g of titanium dioxide;

[0056] (2) Prepare 80 mL of 3.5 M ammonium fluoride aqueous solution, add the waste lithium iron phosphate battery positive electrode powder and titanium dioxide into the ammonium fluoride aqueous solution, and seal;

[0057] (3) Photocatalysis was carried out at 26°C, the UV light source had an operating current of 18A, and the light power density was 1762.5mW / cm 2 The reaction light source uses PLS-SXE300 / 300UV xenon lamp light source with filter, and the constant temperature and constant speed magnetic stirrer is set at 500rpm to ensure full contact of the reactants;

[0058] (4) After irradiation for 12 hours, the precipitate is separated from the solution to obtain a solution containing lithium ions.

[0059] Comparative Example 1

[0060] The same as Example 1, except that the ammonium fluoride aqueous solution in step (2) is replaced by a mixed solution of acetonitrile and dichloromethane solution, specifically: after mixing 30 mL of acetonitrile and 10 mL of dichloromethane solution, the waste lithium iron phosphate battery positive electrode powder and titanium dioxide are added to the mixed solution and sealed.

[0061] Comparative Example 2

[0062] A method for catalytically extracting lithium from a lithium iron phosphate battery without light, comprising the following steps:

[0063] (1) Weigh 0.1g of waste lithium iron phosphate battery positive electrode powder and 0.05g of titanium dioxide;

[0064] (2) Prepare 50 mL of 2M ammonium fluoride aqueous solution, add the waste lithium iron phosphate battery positive electrode powder and titanium dioxide into the ammonium fluoride aqueous solution, and seal;

[0065] (3) Stirring at 25°C with the stirrer speed set to 400 rpm;

[0066] (4) After stirring for 8 hours, the impurities were filtered out and the remaining solution did not contain lithium ions, that is, no lithium ions were detected.

[0067] Comparative Example 3

[0068] The same as Example 3, except that no light is applied, and the solution is stirred only with a constant temperature and constant speed stirrer under natural light conditions to perform catalytic extraction.

[0069] The extraction rates of lithium ions in the solutions prepared in the above examples and comparative examples are shown in Table 1.

[0070] Table 1 Lithium ion extraction rate E Li (%)

[0071] Example <![CDATA[E Li (%)]]> Example 1 62.0 Example 2 77.8 Example 3 89.3 Example 4 61.3 Example 5 70.8 Comparative Example 1 48.0 Comparative Example 2 0 Comparative Example 3 13.9

[0072] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light, characterized in that: The following steps are involved: Adding waste lithium iron phosphate battery cathode powder and photocatalyst into the extract, sealing, photocatalyzing under ultraviolet light, separating the precipitate and the solution after irradiation, and obtaining a lithium-containing solution; The photocatalyst is titanium dioxide; The extracting solution is an ammonium fluoride solution.

2. The method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light according to claim 1, characterized in that: The mass ratio of the waste lithium iron phosphate battery positive electrode powder to the photocatalyst is 1: (0.1-1).

3. The method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light according to claim 1, characterized in that: The concentration of the ammonium fluoride solution is 1-10M.

4. The method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light according to claim 1, characterized in that: The conditions of the photocatalysis are: temperature 20-30°C, working current 13-20A, light power density 1200-2100mW / cm 2 , photocatalytic time 1-24h.

5. The method for photocatalytic extraction of lithium from lithium iron phosphate batteries under ultraviolet light according to claim 1, characterized in that: During the photocatalytic process, the reactor is subjected to cooling circulation treatment.