Method for removing aluminum from black powder of lithium iron phosphate battery and method for recycling battery

Abstract

The invention provides a method for removing aluminum from lithium iron phosphate battery black powder and a battery recycling method. The method comprises the following steps: S1, stirring and mixing the lithium iron phosphate battery black powder and deionized water, adjusting the mixture to a preset pH value by using an agent A, adding an agent B, mixing, heating, reacting for a first preset time, and carrying out solid-liquid separation to obtain Li-containing filtrate and crude iron phosphate slag; s2, performing two-step impurity removal on the L -containing filtrate by using an agent C; s3, after impurity removal, aluminum ions are further removed through resin until the aluminum ions are completely removed; s4, the Li filtrate is evaporated and concentrated until the lithium ion content is lower than the preset concentration, the purified Li solution is precipitated into lithium carbonate through an agent D, heating reaction is conducted for the second preset time, and a crude lithium carbonate product is obtained after solid-liquid separation. The process for preparing the battery-grade lithium carbonate after aluminum impurity removal is simple and easy to operate, and the method can be applied to the industry on a large scale.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a method for removing aluminum from black powder in lithium iron phosphate batteries and a method for recycling batteries. Background Art

[0002] Lithium-ion batteries are widely used in pure / hybrid electric vehicles and various electronic devices due to their advantages such as high operating voltage, long cycle life, and no memory effect. Among them, lithium iron phosphate batteries, as a simple and safe power source, have high cycle performance and do not contain precious metals. They occupy a large market share in power batteries, and their demand in the fields of new energy, base station energy storage, etc. is growing explosively. However, the service life of lithium-ion batteries is generally 5 to 7 years, and a large number of waste lithium iron phosphate batteries will be generated in the next few years. Lithium iron phosphate positive electrode materials have the highest value in battery cells. Improving the economic efficiency of recycling retired batteries lies in preparing the lithium, iron, and phosphorus components in waste lithium iron phosphate positive electrode material powder into battery-grade lithium salts and iron phosphate products through chemical methods, realizing efficient recovery and high-value utilization of lithium iron phosphorus components, which can be used as raw materials for preparing new lithium iron phosphate positive electrode materials.

[0003] To remove aluminum impurities from waste lithium iron phosphate positive electrode materials, this method will inevitably cause a large loss of iron and phosphorus in lithium iron phosphate. Therefore, there is a great challenge in how to efficiently remove aluminum impurities from waste lithium iron phosphate battery black powder while ensuring the integrity of the iron phosphate structure. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problems and provide a method for removing aluminum from black powder in lithium iron phosphate batteries and a method for recycling batteries.

[0005] The technical solution of the present invention is achieved in this way:

[0006] In a first aspect, the present invention provides a method for removing aluminum from black powder of a lithium iron phosphate battery, comprising the following steps:

[0007] S1: Stir and mix lithium iron phosphate battery black powder and deionized water, adjust the pH value to 2-2.5 with reagent A, add reagent B, mix and heat, react for a first predetermined time, perform solid-liquid separation, and obtain Li-containing filtrate and crude iron phosphate slag;

[0008] S2: using reagent C to remove impurities from the Li-containing filtrate in two steps;

[0009] S3: After impurities are removed, the aluminum ions are further removed using resin until the aluminum ions are completely removed;

[0010] S4: evaporating and concentrating the Li filtrate until the lithium ion content is at a predetermined concentration, precipitating the purified Li solution into lithium carbonate with agent D, heating the reaction for a second predetermined time, and obtaining a crude lithium carbonate product after solid-liquid separation; wherein the agent A is one of sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid; the agent B is one of hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid, potassium permanganate, and ammonium persulfate; the agent C is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; and the agent D is sodium carbonate.

[0011] The advantages or beneficial effects of the above technical solution include at least:

[0012] (1) The present invention discloses a method of adding agent A and agent B to lithium iron phosphate battery black powder to react at a certain temperature to generate iron phosphate, thereby separating lithium ions from lithium iron phosphate powder; at the same time, agent A reacts with aluminum to convert aluminum impurities into aluminum ions and remove them from iron phosphate slag. The method is simple to operate, and the two-step impurity removal is combined with resin impurity removal to remove aluminum impurities from the lithium-containing solution. In addition, the structure of the iron phosphate can be ensured not to be destroyed and impurities will not be introduced during the aluminum removal process.

[0013] (2) The present invention discloses that lithium ions and aluminum impurities are separated from lithium iron phosphate positive electrode materials by using reagents A and B, and the separated iron phosphate slag can also be recycled to prepare iron phosphate.

[0014] (3) Since the process for preparing battery-grade lithium carbonate after removing aluminum impurities disclosed in the present invention is simple and easy to operate, it can be applied to industry on a large scale.

[0015] In a second aspect, the present invention further provides a method for recycling batteries, the method comprising the above-mentioned method for removing aluminum from black powder of lithium iron phosphate batteries.

[0016] The advantages or beneficial effects of the above technical solution include at least:

[0017] The battery recycling method of this embodiment has the same beneficial effects as the above-mentioned method for removing aluminum from black powder in lithium iron phosphate batteries, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings illustrate exemplary embodiments of the present invention and together with the description serve to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification.

[0019] Figure 1 This is a flow chart of preparing crude lithium carbonate by removing aluminum impurities from black powder of lithium iron phosphate battery in Example 1 disclosed by the present invention; DETAILED DESCRIPTION

[0020] Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] A method for removing aluminum from black powder of a lithium iron phosphate battery comprises the following steps:

[0023] S1: Stir and mix lithium iron phosphate battery black powder and deionized water, adjust the pH value to 2-2.5 with reagent A, add reagent B, mix and heat, react for a first predetermined time, perform solid-liquid separation, and obtain Li-containing filtrate and crude iron phosphate slag;

[0024] S2: using reagent C to remove impurities from the Li-containing filtrate in two steps;

[0025] S3: After impurities are removed, the aluminum ions are further removed using resin until the aluminum ions are completely removed;

[0026] S4: evaporating and concentrating the Li filtrate until the lithium ion content is at a predetermined concentration, precipitating the purified Li solution into lithium carbonate with agent D, heating the reaction for a second predetermined time, and obtaining a crude lithium carbonate product after solid-liquid separation; wherein the agent A is one of sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid; the agent B is one of hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid, potassium permanganate, and ammonium persulfate; the agent C is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; and the agent D is sodium carbonate.

[0027] In step S1, preferably, reagent A is hydrochloric acid until its pH is within the range of 2 to 2.5, and the preferred pH value is 2. The change in pH will affect the leaching rate of Li, Fe, P, and Al elements, so that the Li element can be leached to the greatest extent;

[0028] In step S1, preferably, the agent B is an oxidant, specifically, the agent B is an ammonium persulfate solution, which can effectively convert divalent iron into trivalent iron, thereby promoting the separation of lithium ions; preferably, the pH value is preferably 2, and the stirring and mixing process parameters are: the rotation speed is 300-400 rpm; the time is 20-30 min;

[0029] Preferably, the liquid-to-solid ratio of the deionized water to the lithium iron phosphate black powder is 9.1:1; preferably, the first predetermined time is 1 to 3 hours, and the temperature of the heating reaction is 50 to 90° C.;

[0030] Preferably, the solid-liquid separation method comprises: filtering and washing the mixture, separating the washed liquid, and obtaining an aluminum-containing lithium liquid; Preferably, the lithium iron phosphate battery black powder is obtained by discharging, disassembling and crushing waste lithium iron phosphate batteries.

[0031] In step S2, preferably, the reagent C is sodium hydroxide, which is used to convert the precipitated aluminum ions into aluminum hydroxide precipitates;

[0032] In step S4, preferably, the reagent D is a precipitant for reacting with lithium ions to generate lithium carbonate precipitate; preferably, the second predetermined time is 1 to 3 hours, and the temperature of the heating reaction is 50 to 90°C.

[0033] In the method, the leaching rates of Li and Al and the loss rates of Fe and P under different pH value ranges and the comparison with the existing method are shown in Table 1:

[0034] Table 1

[0035]

[0036] It can be seen from Table 1 that when the pH value is controlled at 2, the leaching rates of Li and Al can be guaranteed while the loss rates of Fe and P can be controlled to a minimum. In the existing methods, the loss rates of Fe and P are both 10%, while the method of the present application can control them to below 5%.

[0037] Example 1

[0038] A new process for removing aluminum from black powder of lithium iron phosphate batteries, such as Figure 1 As shown, the following steps are included:

[0039] S1. Discharging, disassembling and crushing waste lithium iron phosphate batteries to obtain waste lithium iron phosphate battery black powder, wherein the black powder contains aluminum because aluminum shell powder is mixed into it when the battery is crushed and disassembled, and the obtained lithium iron phosphate battery black powder is added with deionized water with a mass of 9.1 times that of the lithium iron phosphate battery black powder and loaded into a stirring tank, and a certain amount of agent A is added into the stirring tank, and the agent A is used to adjust the pH value, and then the rotation speed is 300-400rpm, and the final pH is determined after stirring for 20min, and agent B is added to the lithium iron phosphate mixed solution, reacting for 1-3h, and heating to 50-90°C, and the obtained solution is solid-liquid separated to obtain Li-containing filtrate and crude iron phosphate slag, wherein iron and phosphorus can be recovered in the crude iron phosphate slag to avoid a large amount of iron and phosphorus loss, and agent B is an oxidant, in order to convert divalent iron into trivalent iron, thereby promoting the separation of lithium ions, as preferably, agent B is ammonium persulfate solution.

[0040] S2, the obtained lithium solution is loaded into the impurity removal tank, and the reagent C is added for two-step impurity removal, wherein the purpose of the two-step impurity removal is to precipitate most of the Al ions, thereby removing the Al ions. Specifically, the steps of the two-step impurity removal are: first, the pH value is adjusted to 7 with the reagent C, and then the pH value is adjusted to 10, so as to achieve the purpose of converting the precipitated aluminum ions into aluminum hydroxide precipitation. As a preferred embodiment, the reagent C is a sodium hydroxide solution for regulating the pH. In the two-step impurity removal, the first step of adjusting the pH value to 7 is to provide a neutral environment to remove impurity salts, hydroxides and excess impurity removal agents, and the second step of adjusting the pH value to 10 (or higher) is to use the characteristics of certain ions that are more likely to form precipitation in an alkaline environment to remove impurities that are difficult to remove, and on the other hand, it is also to prepare an alkaline environment for lithium precipitation.

[0041] S3. After the regulation is completed, the lithium liquid after two steps of impurity removal is obtained by filtration and separation, and the obtained lithium liquid is poured into a resin tank for further aluminum removal. The flow rate is controlled to be 5BV / h, wherein the resin in the resin tank is an ion exchange resin. The ion exchange resin can selectively adsorb Al ions without adsorbing other ions in this process, so as to achieve the purpose of completely adsorbing Al ions.

[0042] The aluminum removal principle of step 2 and step 3 is: firstly, most of the Al ions are precipitated out in the form of aluminum hydroxide, and then the remaining Al ions are adsorbed by ion exchange resin, so as to achieve the purpose of completely removing the Al ions.

[0043] S4. The lithium solution obtained in step 2 after impurity removal is evaporated and concentrated to a solution with a certain lithium ion concentration. After adding agent D to the concentrated lithium solution, the temperature is raised to 50-90° C., preferably reacted at 90° C. for 1-3 hours, preferably for 2 hours, and then filtered and washed to obtain wet crude lithium carbonate. Preferably, agent D is sodium carbonate, which is used as a precipitant to generate lithium carbonate precipitate with lithium ions.

[0044] In the above steps, the reagent A may also be one of sulfuric acid, phosphoric acid and nitric acid;

[0045] The agent B may also be an oxidant, which is one of hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid, and potassium permanganate;

[0046] In step S2, the reagent C may also be at least one of potassium hydroxide and ammonia water;

[0047] The present invention also discloses a method for recycling lithium-ion batteries, comprising the steps of the above-mentioned new process for removing aluminum from black powder of lithium iron phosphate batteries;

[0048] Preferably, in step S1, the solid-liquid separation method is: filtering and washing the mixture, separating the washed liquid, and obtaining an aluminum-containing lithium liquid.

[0049] The present invention also discloses another embodiment:

[0050] Example 2

[0051] S1. Discharge, disassemble and crush waste lithium iron phosphate batteries to obtain waste lithium iron phosphate battery black powder, add deionized water with a mass of 9.1 times that of lithium iron phosphate battery black powder to the obtained lithium iron phosphate battery black powder and put them into a stirring tank, add a certain amount of agent A to the stirring tank, preferably, agent A is sulfuric acid, until the pH value is 2, and then the rotation speed is 300-400 rpm, stir for 20 minutes and determine the final pH value, add agent B to the lithium iron phosphate mixed solution, preferably, agent B is hydrogen peroxide solution; react for 1-3 hours, and heat to 50-90° C., separate the obtained solution into solid and liquid to obtain Li-containing filtrate and crude iron phosphate slag.

[0052] S2. The obtained lithium liquid is loaded into a de-impurity tank, and reagent C is added to perform two-step de-impurity. Specifically, reagent C is a sodium hydroxide solution for adjusting pH. In the above two-step de-impurity, the first step of adjusting the pH value to 7 is to provide a neutral environment to remove impurity salts, hydroxides and excess de-impurity reagents, and the second step of adjusting the pH value to 10 (or higher) is to utilize the property that some ions are more likely to form precipitation in an alkaline environment to remove impurities that are difficult to remove, and on the other hand, it is also to prepare an alkaline environment for lithium precipitation.

[0053] S3. After the regulation is completed, the lithium liquid is filtered and separated to obtain the two-step impurity-removed lithium liquid, and the obtained lithium liquid is poured into a resin tank for further aluminum removal, and the flow rate is controlled to be 5BV / h.

[0054] S4. The lithium solution obtained in step 2 after impurity removal is evaporated and concentrated to a solution with a certain lithium ion concentration. After adding agent D to the concentrated lithium solution, the temperature is raised to 50-90° C., preferably reacted at 90° C. for 1-3 hours, preferably for 2 hours, and then filtered and washed to obtain wet crude lithium carbonate. Preferably, agent D is sodium carbonate.

[0055] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present invention.

[0056] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present invention.

Claims

1. A method for removing aluminum from black powder of lithium iron phosphate battery, characterized in that: The following steps are involved: S1: Stir and mix lithium iron phosphate battery black powder and deionized water, adjust the pH value to 2-2.5 with reagent A, add reagent B, mix and heat, react for a first predetermined time, perform solid-liquid separation, and obtain Li-containing filtrate and crude iron phosphate slag; S2: using reagent C to remove impurities from the Li-containing filtrate in two steps; S3: After impurities are removed, the aluminum ions are further removed using resin until the aluminum ions are completely removed; S4: evaporating and concentrating the Li filtrate until the lithium ion content is at a predetermined concentration, precipitating the purified Li solution into lithium carbonate with agent D, heating the reaction for a second predetermined time, and obtaining a crude lithium carbonate product after solid-liquid separation; wherein the agent A is one of sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid; the agent B is one of hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid, potassium permanganate, and ammonium persulfate; the agent C is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; and the agent D is sodium carbonate.

2. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 1, characterized in that: In step S1, the pH value is 2.

3. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 2, characterized in that: In step S1, the stirring and mixing process parameters are: rotation speed is 300-400 rpm; time is 20-30 min.

4. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 3, characterized in that: In step S1, the solid-liquid separation method includes: filtering and washing the mixture, separating the washed liquid, and obtaining an aluminum-containing lithium liquid.

5. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 1, characterized in that: The liquid-to-solid ratio of the deionized water to the lithium iron phosphate black powder is 9.1:

1.

6. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 1, characterized in that: In step S1, the first predetermined time is 1 to 3 hours, and the temperature of the heating reaction is 50 to 90°C.

7. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 1, characterized in that: In step S4, the second predetermined time is 1 to 3 hours, and the temperature of the heating reaction is 50 to 90°C.

8. The method for removing aluminum from black powder of lithium iron phosphate battery according to claim 1, characterized in that: The lithium iron phosphate battery black powder is obtained by discharging, disassembling and crushing waste lithium iron phosphate batteries.

9. A method for recycling batteries, characterized in that: The method comprises the method for removing aluminum from black powder of a lithium iron phosphate battery as claimed in any one of claims 1 to 8.

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