Method for preparing catalyst from positive electrode of lithium iron phosphate battery

Abstract

The invention discloses a method for preparing a catalyst from a lithium iron phosphate battery positive electrode. An iron solution is recovered from a lithium iron phosphate battery positive electrode material; adding the obtained iron solution into a gelatin solution to obtain a catalyst precursor; absorbing the precursor by using rice hull-based white carbon black; and drying, heating and carbonizing to obtain the granular catalyst. The Fe-coated NC catalyst is prepared in situ, and solid waste of a lithium iron phosphate type lithium ion battery positive electrode material is recycled. And through secondary loading, the recoverability of the catalyst is improved.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and more specifically, to the preparation of a nitrogen-doped activated carbon-supported iron catalyst, and in particular to a method for preparing a catalyst from a positive electrode of a lithium iron phosphate battery. Background Art

[0002] Nitrogen-doped activated carbon supported iron (Fe@NC) catalyst can be used for oxygen reduction reaction (ORR) (Lin L, Zhu Q, XuA W. Noble-metal-free Fe-N / C catalyst for highly efficient oxygen reduction reaction under both alkaline and acidic conditions. [J]. Journal of the American Chemical Society, 2014, 136(31): 11027-11033.) The positive electrode material of lithium iron phosphate type lithium ion battery contains more than 28% iron, and it also contains about 4% lithium, 18% phosphorus and 10% carbon. The carbon component and binder component it contains are difficult to convert and reuse. Rice husk white carbon black is a porous silica material prepared from natural products. Compared with silica gel or diatomaceous earth, its particle size is larger and the pore structure is richer. Summary of the invention

[0003] Aiming at the problems of preparation of Fe@NC catalyst and recycling of positive electrode materials of lithium iron phosphate battery, the present invention aims to provide a method for preparing catalyst from positive electrode of lithium iron phosphate battery.

[0004] The object of the present invention is achieved by the following scheme: A method for preparing a catalyst from a positive electrode of a lithium iron phosphate battery comprises the following steps: (1) Dissolving the positive electrode material of the discarded lithium iron phosphate battery in nitric acid, filtering out the insoluble matter to obtain a clear iron solution; (2) preparing a gelatin solution by adding the iron solution obtained in step (1) into the gelatin and stirring until the pH of the solution becomes neutral; (3) absorbing the solution obtained in step (2) with rice husk-based silica; (4) Drying the sludge product obtained in step (3) and then burning it to obtain a catalyst.

[0005] Preferably, the calcination temperature in step (4) is 350°C.

[0006] In step (1), the carbon component and binder component that are difficult to convert and process in the positive electrode material are removed by filtration, and the iron element exists in the form of ions. In step (2), iron coordinates with the nitrogen element in the peptide chain molecule under neutral conditions to form a precursor. In step (3), the precursor is filled into the three-dimensional pore structure of rice husk-based white carbon black. In step (4), the Fe@NC catalyst is generated in situ in the three-dimensional pores by calcination.

[0007] Under the above technical background, we have invented a method for preparing a catalyst from a positive electrode of a lithium iron phosphate battery, aiming at the preparation of Fe@NC catalyst and the recycling and reuse of positive electrode materials of lithium iron phosphate batteries. The advantages of the present invention are as follows: (1) In situ preparation of Fe@NC catalyst to achieve the recycling of solid waste of lithium iron phosphate type lithium-ion battery cathode materials.

[0008] (2) The recyclability of the catalyst is improved through secondary loading. DETAILED DESCRIPTION

[0009] The present invention will be further described below in conjunction with specific examples. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0010] Example 1 A method for preparing a catalyst from a positive electrode of a lithium iron phosphate battery comprises the following steps: (1) Preparation of iron solution from the positive electrode material of lithium iron phosphate battery: The lithium iron phosphate battery was exhausted, the battery was disassembled in a drying room, and the positive electrode was taken out, rinsed with pure water and dried; 0.3 g of the dried positive electrode was taken and immersed in pure water for 2 h, and the active material layer was peeled off from the aluminum foil by ultrasonic treatment for 20 min; the active material layer was collected and placed in a polytetrafluoroethylene beaker, and 10 mL of pure water and 3 mL of commercial concentrated nitric acid were added in sequence; the beaker was placed in a fume hood and heated on a 175°C heating plate until the liquid in it completely disappeared; after the beaker cooled, 10 mL of pure water and 50 uL of commercial concentrated nitric acid were added again, the solution was filtered after being fully stirred with a glass rod, and the insoluble matter was filtered out to obtain a clear iron solution; the iron solution contained about 80 mg of iron element, and the pH ≈ 2.5; (2) Preparation of catalyst precursor: In a 200 mL beaker, add 10 g of gelatin and 100 mL of pure water, heat to 50 °C and stir for 2 h to prepare a gelatin solution. This solution can also be prepared and used immediately. After the solution is allowed to stand for 30 min, 10 mL of the upper layer is drawn and injected into the iron solution obtained in step (1), and then stirred rapidly for 30 min. The H in the iron solution is reduced. + The ions are neutralized by the active nitrogen in the gelatin to obtain a solution with a neutral pH value of pH ≈ 7. After stirring, the solution becomes slightly turbid, which is the catalyst precursor solution. (3) Absorption of precursor solution with rice husk-based white carbon black: 6 mL of the catalyst precursor solution obtained in the rice husk-based silica absorption step (2) is added dropwise onto 2 g of rice husk-based silica, the precursor solution is absorbed by the rice husk-based silica, and the excess precursor solution is removed by filter paper to obtain a slurry-like fluid product; (4) In-situ generation of catalyst: The slurry-like fluid product obtained in step (3) was placed in a quartz beaker, dried in a forced air drying oven at 65°C, and then heated to 350°C at a rate of 8°C / min, burned and kept warm for 2 h, and then cooled to room temperature to obtain a gray-black granular supported Fe@NC catalyst. Table 1 compares the amount of residual catalyst in this catalyst and Fe@NC (prepared in the same way) without secondary loading of rice husk-based white carbon black after multiple rounds of simulated recovery experiments. .

[0011] The above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst from a lithium iron phosphate battery positive electrode, characterized in that: The steps include: (1) dissolving the cathode material of the discarded lithium iron phosphate battery in nitric acid, filtering out insoluble matter to obtain a clarified iron solution; (2) preparing a gelatin solution, adding the iron solution obtained in step (1) to the gelatin solution and stirring to obtain a solution with a neutral pH; (3) absorbing the solution obtained in step (2) with rice husk-based white carbon black to obtain a mud-like product; (4) Drying the mud product obtained in step (3) and then burning it to obtain a catalyst.

2. The method for preparing a catalyst from a positive electrode of a lithium iron phosphate battery according to claim 1, characterized in that: The calcination temperature in step (4) is 350°C.

3. The method for preparing a catalyst from a positive electrode of a lithium iron phosphate battery according to claim 1 or 2, characterized in that: The steps include: (1) Preparation of iron solution from the positive electrode material of lithium iron phosphate battery The lithium iron phosphate battery was exhausted, the battery was disassembled in a drying room, and the positive electrode was taken out, rinsed with pure water and dried; 0.3 g of the dried positive electrode was taken and immersed in pure water for 2 h, and the active material layer was peeled off from the aluminum foil by ultrasonic treatment for 20 min; the active material layer was collected and placed in a polytetrafluoroethylene beaker, and 10 mL of pure water and 3 mL of commercial concentrated nitric acid were added in sequence; the beaker was placed in a fume hood on a 175°C heating plate and heated openly until the liquid in it completely disappeared, and the beaker was cooled and 10 mL of pure water and 50 uL of commercial concentrated nitric acid were added again, and the solution was filtered after being fully stirred with a glass rod. The solution contained about 80 mg of iron and pH ≈ 2.5; (2) Preparation of catalyst precursor Add 10 g of gelatin and 100 mL of pure water in a 200 mL beaker, heat to 50°C and stir thoroughly for 2 h. This gelatin solution can be used freshly prepared. After the solution is allowed to stand for 30 min, 10 mL of the upper layer is drawn and injected into the iron solution obtained in step (1), and then stirred rapidly for 30 min. The H in the iron solution is reduced. + The ions are neutralized by the active nitrogen in the gelatin, the solution pH ≈ 7, and it is slightly turbid after stirring. This is the catalyst precursor solution; (3) Absorption of precursor solution by rice husk-based silica 6 mL of the precursor solution obtained in the extraction step (2) was added dropwise onto 2 g of rice husk-based silica, the precursor solution was absorbed by the rice husk-based silica, and the excess precursor solution was removed by filter paper to obtain a slurry-like fluid; (4) In-situ generation of catalyst The slurry obtained in step (3) was placed in a quartz beaker, dried at 65°C in a forced air drying oven, and then heated to 350°C at a rate of 8°C / min, kept at that temperature for 2 h, and then cooled to room temperature to obtain a gray-black granular supported Fe@NC catalyst.