Method for repairing and regenerating waste lithium iron phosphate positive electrode material

Abstract

The invention relates to a repair and regeneration method of a waste lithium iron phosphate positive electrode material, and belongs to the technical field of battery material recycling, the repair and regeneration method provided by the invention comprises the following steps: stirring and uniformly mixing the waste lithium iron phosphate positive electrode material, a lithium salt and an additive in water to obtain a mixed solution substance A; putting the substance A into a reaction kettle, sealing, vacuumizing, heating the reaction kettle, cooling, filtering and washing to obtain a substance B; and sintering the substance B under a nitrogen protection condition to obtain the regenerated lithium iron phosphate positive electrode material. The waste lithium iron phosphate positive electrode material is repaired and regenerated through a hydrothermal repair method, the obtained regenerated lithium iron phosphate positive electrode material is uniform in particle, the lithium ion battery prepared from the material is relatively high in specific capacity and excellent in cycle performance, and the preparation method is green and simple in process, low in cost, low in energy consumption and wide in application prospect.

Description

Technical Field

[0001] The invention relates to a repair and regeneration method for waste lithium iron phosphate positive electrode materials, belonging to the technical field of lithium ion battery material recycling. Background Art

[0002] Lithium iron phosphate batteries are widely used in electric vehicles, hybrid vehicles, and new electrochemical energy storage fields due to their low toxicity, low cost, good cycle performance, and excellent safety performance. With the large-scale application of lithium iron phosphate batteries, the recycling and reuse of waste lithium iron phosphate batteries have received increasing attention. Improper handling will lead to serious waste of resources and environmental pollution.

[0003] At present, the recycling process of waste lithium iron phosphate batteries still has certain limitations, mainly due to the long recycling process cycle, low economic benefits and recycling efficiency. The existing technology mainly recovers the valuable lithium elements in lithium iron phosphate materials, but the recycling efficiency is low and the product purity is not high, and it is impossible to achieve effective recycling and reuse of all components. Therefore, it is of great significance to develop a repair, regeneration and recycling method for waste lithium iron phosphate battery materials that is both economical, efficient and universal to achieve sustainable utilization of lithium iron phosphate. Summary of the invention

[0004] The purpose of the present invention is to provide a method for repairing and regenerating waste lithium iron phosphate positive electrode materials, so as to repair the electrochemical properties of waste lithium iron phosphate materials and realize the efficient recycling of lithium iron phosphate materials.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for repairing and regenerating waste lithium iron phosphate positive electrode materials, comprising the following steps:

[0007] Step 1, firstly, stirring and mixing waste lithium iron phosphate positive electrode material, lithium salt and additive in water to obtain a mixed solution substance A;

[0008] Step 2, placing substance A in a reaction kettle, sealing and evacuating the kettle, then heating the reaction kettle, cooling the reactor, filtering and washing the reactor, and obtaining substance B;

[0009] Step 3, sintering substance B under nitrogen protection conditions to obtain regenerated lithium iron phosphate positive electrode material.

[0010] The lithium salt in step 1 is one or more of lithium carbonate, lithium iodide, lithium nitrate, lithium hydroxide, lithium oxalate, lithium acetate, and lithium chloride; preferably lithium iodide or lithium hydroxide, and more preferably lithium iodide.

[0011] In step 1, the total molar ratio of lithium element in the lithium salt and lithium iron phosphate waste to the molar ratio of iron element Li / Fe=1.05:1-3:1, and the preferred molar ratio Li / Fe=2:1.

[0012] The additive in step 1 is glucose. The mass ratio of the additive to the waste lithium iron phosphate positive electrode material is 0.1 to 0.3, and the preferred mass ratio is 0.2.

[0013] In step 2, the heat treatment temperature of the reactor is 120-200°C, preferably 160-200°C, and more preferably 200°C.

[0014] The heat treatment time in the reactor is 1 to 5 hours, preferably 3 to 5 hours, and more preferably 5 hours.

[0015] In step 3, the sintering temperature is 400-800°C, preferably 600-700°C, and more preferably 650°C; the calcination time is 1-5h, preferably 2-3h, and more preferably 2h; the heating rate is 2-10°C / min, preferably 5°C / min.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a method for repairing and regenerating waste lithium iron phosphate battery positive electrode materials. The method uses a hydrothermal method to directly repair and regenerate the waste lithium iron phosphate positive electrode materials without destroying their structure. By adjusting parameters such as the hydrothermal repair temperature and the amount of additives used, the repair of the failed lithium iron phosphate crystal structure and the improvement of electrochemical performance are effectively achieved. The additives added during the repair process significantly improve the rate and cycle performance of lithium iron phosphate.

[0018] The repair and regeneration method of the lithium iron phosphate positive electrode material provided by the present invention has simple process, short flow, no pollution, low energy consumption, and saves recycling costs. It is of great significance for the large-scale industrial recovery and high-value reuse of waste lithium iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process of repairing and regenerating waste lithium iron phosphate positive electrode materials according to Examples 1 to 6. DETAILED DESCRIPTION

[0020] In order to clearly illustrate the technical features of the present solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings. In the following description, many specific details are described to facilitate a full understanding of the present application. However, the present application can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0021] (I) Waste lithium iron phosphate raw materials

[0022] The raw materials used in the experiment are from waste lithium iron phosphate battery soft-pack batteries. The lithium iron phosphate positive electrode waste of the battery is collected, and its elemental composition is shown in Table 1.

[0023] Table 1 Metal element composition of waste

[0024] Quality score Li Fe P Al Quality score 3.553 34.863 18.581 0.613 Molar Ratio 0.82 1.00 0.96 0.04

[0025] (II) Experimental methods

[0026] 1. If Figure 1 As shown, the method for repairing and regenerating waste lithium iron phosphate positive electrode materials in this application is as follows:

[0027] (1) First, waste lithium iron phosphate positive electrode material, lithium salt, and additives are stirred and mixed in water according to a certain ratio to obtain a mixed solution substance A;

[0028] (2) placing the uniformly mixed solution substance A in a reaction kettle, filling the reaction kettle with nitrogen, sealing the reaction kettle, placing the reaction kettle at a certain temperature for a certain time, cooling, filtering, washing, and drying to obtain substance B;

[0029] (3) Sintering material B under nitrogen protection to obtain regenerated lithium iron phosphate positive electrode material.

[0030] 2. Comparative experiments: In one experiment, the waste lithium iron phosphate positive electrode material obtained was not subjected to the treatment of steps (1) to (3); in another experiment, the waste lithium iron phosphate positive electrode material obtained was subjected to the treatment of step (1) without adding additives.

[0031] 3. Testing: The regenerated lithium iron phosphate positive electrode material obtained in step (3) of the present application is used to assemble a lithium-ion battery, and its first-week reversible discharge capacity is tested by charge and discharge.

[0032] (III) Experimental data and results

[0033] 1. Examples 1-6 are the experimental data and results of the products obtained by the regeneration method of the present application, and Examples 7-8 are the experimental data and results of the comparative experiments. The comparative experiments are conducted based on Example 1. The experimental data and results of Examples 1-8 are specifically shown in Table 2.

[0034] Table 2 Experimental data and results of the repair and regeneration method of waste lithium iron phosphate positive electrode materials

[0035]

[0036]

[0037] From the experimental data and results analysis in Table 2, we can see that:

[0038] It can be seen from Examples 1-6 and 7 that after the regenerated lithium iron phosphate positive electrode material obtained after the treatment of steps (1)-(3) of the present application and the untreated waste lithium iron phosphate positive electrode material were subjected to charge and discharge tests respectively, the first-week reversible discharge specific capacity of the former was greatly increased.

[0039] It can be seen from Examples 1-6 that after being processed in steps (1)-(3) of the present application, the first-week reversible discharge capacity of the obtained regenerated lithium iron phosphate positive electrode material is significantly increased, and the repair and regeneration of the waste lithium iron phosphate positive electrode material is better achieved.

[0040] It can be seen from Examples 1 and 5 that, within a certain range, increasing the reactor heat treatment temperature and time is helpful to increase the first-week reversible discharge specific capacity of the regenerated lithium iron phosphate positive electrode material.

[0041] It can be seen from Examples 2 and 3 that lithium iodide, as opposed to lithium carbonate, helps increase the first-week reversible discharge specific capacity of the regenerated lithium iron phosphate positive electrode material.

[0042] It can be seen from Examples 2 and 4 that, within a certain range, increasing the amount of additives helps to increase the first-week reversible discharge specific capacity of the regenerated lithium iron phosphate positive electrode material. It is speculated that the increase in the amount of additives may be beneficial to maintaining a low-potential atmosphere in the solution and to the complete conversion of iron phosphate in the waste into lithium iron phosphate.

[0043] It can be seen from Examples 2 and 8 that the addition of additives in step (1) significantly increases the first-cycle reversible discharge specific capacity of the regenerated lithium iron phosphate positive electrode material.

[0044] According to the method for repairing and regenerating waste lithium iron phosphate positive electrode materials of the present application, it can be seen from step (2) that after the reactor is heat treated, it needs to undergo a water washing process, and the lithium salt and additives can be dissolved in water. Therefore, according to the first week reversible discharge capacity results of Examples 2 and 7, it can be seen that the lithium salt and additives are not simply mixed with the waste lithium iron phosphate materials.

[0045] 2. In order to further explore whether lithium salt is added to the waste lithium iron phosphate material, the regenerated lithium iron phosphate positive electrode material A of Example 2 and the waste lithium iron phosphate positive electrode material A' of Comparative Example 7 were subjected to metal element detection and analysis, and the results in Table 3 below were obtained.

[0046] Table 3 Element molar ratio analysis results of samples A and A'

[0047] sample Li / Fe Li / P A 0.9995 0.9894 A' 0.8166 0.8058

[0048] It can be seen from Table 3 that the ratio of Li / Fe in the regenerated lithium iron phosphate positive electrode material is close to 1, and the regenerated lithium iron phosphate positive electrode material obtained after the waste lithium iron phosphate, lithium salt and additives are repaired is not a simple mixture. Therefore, it is speculated that the heat treatment adds lithium elements to the waste lithium iron phosphate material, thereby repairing the structure of the lithium iron phosphate material, and then changing the physicochemical properties and electrochemical properties of the regenerated lithium iron phosphate positive electrode material.

[0049] The repair and regeneration method of waste lithium iron phosphate positive electrode materials of the present application is low-cost, simple to operate, efficient and environmentally friendly; the regenerated lithium iron phosphate material obtained by the repair and regeneration method of the present application has excellent physical and chemical properties and electrochemical properties, which is conducive to the recycling of waste lithium iron phosphate battery positive electrode materials.

[0050] The above specific implementations cannot be used as limitations on the scope of protection of the present invention. For those skilled in the art, any replacement, improvement or change made to the implementations of the present invention falls within the scope of protection of the present invention. The parts not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for repairing and regenerating waste lithium iron phosphate positive electrode materials, characterized in that: The following steps are involved: Step 1, firstly, stirring and mixing waste lithium iron phosphate positive electrode material, lithium salt and additive in water to obtain a mixed solution substance A; Step 2, placing substance A in a reaction kettle, sealing and evacuating the kettle, then heating the reaction kettle, cooling the reactor, filtering and washing the reactor, and obtaining substance B; Step 3, sintering substance B under nitrogen protection conditions to obtain regenerated lithium iron phosphate positive electrode material. The lithium salt in step 1 is one or more of lithium carbonate, lithium iodide, lithium nitrate, lithium hydroxide, lithium oxalate, lithium acetate, and lithium chloride; The additive is glucose.

2. The repair and regeneration method according to claim 1, characterized in that: The total molar ratio of lithium element to iron element in the lithium salt and lithium iron phosphate waste is Li / Fe=1.05:1-3:

1.

3. The repair and regeneration method according to claim 1, characterized in that: The mass ratio of the additive to the waste lithium iron phosphate positive electrode material is 0.1 to 0.

3.

4. The repair and regeneration method according to claim 1, characterized in that: The heat treatment temperature of the reactor is 120-200° C., and the time is 1-5 hours.

5. The repair and regeneration method according to claim 1, characterized in that: The sintering temperature of the substance B is 400-800° C., and the sintering time is 1-5 hours.

6. The repair and regeneration method according to claim 3, characterized in that: The heating rate to the sintering temperature is 2-10°C / min.

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