Recycling method of positive plate of waste lithium ion battery

Abstract

The invention discloses a recycling method of a positive plate of a waste lithium ion battery, and relates to the technical field of resource recycling of the waste lithium ion battery. The method comprises the following steps: (1) pretreatment of the waste lithium ion battery: discharging, disassembling and crushing the waste lithium ion battery to obtain positive plate scraps; (2) catalytic leaching of the positive plate chippings: preparing a leaching agent solution from acid, an iron-containing compound and a chlorine-containing compound, adding the positive plate chippings into the leaching agent solution for reaction, and filtering to obtain a leaching solution; (3) iron and aluminum in the leachate are separated, specifically, an alkali solution is added to increase the pH of the leachate to precipitate iron and aluminum, and precipitates containing iron and aluminum and a valuable metal solution are obtained through filtering separation; and (4) recovery of the catalyst: putting the iron-aluminum precipitate into an alkali solution, dissolving an aluminum element, and filtering to obtain an iron precipitate. The process flow is simple, no extra reducing agent needs to be added, and recovery of all metal elements in the positive plate is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of resource recovery and utilization of waste lithium-ion batteries, and in particular to a method for leaching positive plates of waste lithium-ion batteries by utilizing iron ions for catalytic leaching. Background Art

[0002] Lithium-ion batteries are widely used in electric vehicles, mobile phones, communications and other industries due to their high operating voltage, long life and high energy density. With the widespread use of electric vehicles and handheld devices in recent years, the production of lithium batteries has also increased dramatically. According to statistics from the World Energy Organization, the global production of pure electric vehicles increased from 16,000 in 2010 to 4.79 million in 2019. The lithium-ion batteries used will fail and be scrapped for various reasons after 3-10 years, generating a large number of waste lithium-ion batteries. Since the toxic substances such as electrolytes contained in waste lithium-ion batteries will pollute the environment, and the metal elements lithium, cobalt, nickel or manganese contained therein have high value, it is necessary to reasonably recycle waste lithium-ion batteries.

[0003] Waste lithium-ion batteries are mainly composed of positive electrode sheets, negative electrode sheets, separators, electrolytes, battery shells, etc. Valuable metals lithium, cobalt, nickel, and manganese as components of positive electrode active materials are mainly concentrated in the positive electrode sheets. Common positive electrode active materials for lithium-ion batteries include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2), lithium nickel cobalt aluminum oxide (LiNi a Co b Al 1-a-b O2), lithium-rich manganese-based (cLi2MnO3·(1-c)LiMO2), etc. The positive electrode active material is adhered to the aluminum foil current collector through the binder PVDF to form a complete positive electrode sheet. Researchers have developed a large number of wet processes for the recovery of positive electrode sheets, among which the positive electrode active material stripping and acid leaching process are currently the most common methods, which generally have the following steps:

[0004] (1) removing the organic binder PVDF in the positive electrode sheet by calcination or dissolution with an organic solvent, and separating the positive electrode active material from the aluminum foil;

[0005] (2) using an acid leaching agent to leach the positive electrode active material to obtain a metal salt solution;

[0006] (3) Recovering metal elements from metal salt solutions through processes such as precipitation, extraction or electrodeposition to prepare products.

[0007] For the stripping of positive electrode active materials, the roasting method requires a high temperature of more than 400°C and produces harmful gases containing fluorine. The organic solvent dissolution method is costly and produces volatile organic pollutants. For the leaching step of positive electrode active materials, since most of the valuable metal elements in the positive electrode active materials exist in a higher valence state, such as the cobalt element in LiCoO2 is +3 valence, it is usually necessary to add a reducing agent to reduce these high-valent metals during the acid leaching process to obtain a higher leaching rate. For example, Chinese patent CN201510242788 uses organic acid to leach positive electrode active materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide, and adds sulfurous acid, sodium sulfite or hydrogen peroxide as a reducing agent. In order to avoid the use of additional reducing agents, Chinese patent CN201910166805 discloses a method of directly reducing high-valent metal elements in the positive electrode active material by using the aluminum foil current collector in the positive electrode sheet. The crushed positive electrode sheet powder is roasted in a non-oxidizing atmosphere at 400℃-750℃ to achieve in-situ reduction of the positive electrode active material by aluminum foil. Then, the roasted products are leached by alkaline leaching and acid leaching respectively to achieve the leaching of valuable metals. However, the use of high temperature will cause PVDF to decompose and produce harmful gases, while increasing energy consumption.

[0008] In summary, the current recycling of waste lithium-ion battery positive plates still has the following problems: (1) The positive active material stripping process is time-consuming and highly polluting; (2) Acid leaching of positive active materials requires the addition of expensive reducing agents, which increases process costs; (3) The in-situ reduction method of aluminum foil current collectors still requires high temperatures, causing pollution and increasing energy consumption. These problems seriously limit the efficient resource utilization of waste lithium-ion batteries. Summary of the invention

[0009] In order to solve the above problems, the present invention provides a simple, efficient and low-cost wet recovery process for positive electrode sheets, which uses iron ion catalysis to achieve aluminum foil reduction of positive electrode active substances at room temperature. The process includes the following steps:

[0010] S1: Pretreatment of waste lithium-ion batteries: discharging the waste lithium-ion batteries, disassembling them to obtain positive electrode sheets, and finally crushing the positive electrode sheets to obtain positive electrode sheet fragments.

[0011] S2: Catalytic leaching of waste lithium-ion battery positive plates: A leaching agent solution is prepared using acid, iron-containing compounds and chlorine-containing compounds. The concentration of the leaching agent solution is 0.05-10 mol / L. The positive plate fragments are added to the leaching agent solution. After stirring at room temperature for 20 minutes, the leaching solution rich in metal elements is filtered.

[0012] S3: Separating the iron and aluminum in the leachate: adding an alkaline solution to raise the pH of the leachate to 5-7 to precipitate iron and aluminum, filtering and separating to obtain a precipitate containing iron and aluminum and a solution containing valuable metals. Specifically, the pH may be 5.6, 5.9, 6, 6.5 or 7.

[0013] S4: Recycling of catalyst: Put the iron-aluminum precipitate into an alkaline solution with a pH greater than 12 to dissolve the aluminum element. After filtering, the iron precipitate is obtained and put into the next batch of catalytic leaching experiments.

[0014] The present invention found that by using chloride ions to remove the oxide layer on the surface of the aluminum foil current collector under acidic conditions, and then using iron ions as a catalyst, the aluminum foil current collector can achieve in-situ reduction of high-valent metal elements in the positive electrode active material at room temperature, avoiding the cumbersome positive electrode active material stripping steps and the use of expensive reducing agents in traditional processes, and achieving the simultaneous recovery of positive electrode active materials and aluminum foil. Various battery positive electrode sheet debris undergo the following chemical reactions during the leaching process:

[0015] LiCoO2+Fe 2+ +4H + =Li + +Co 2+ +Fe 3+ +2H2O

[0016] LiNiO2+Fe 2+ +4H + =Li + +Ni 2+ +Fe 3+ +2H2O

[0017] LiMn2O4+3Fe 2+ +8H + =Li + +2Mn 2+ +3Fe 3+ +2H2O

[0018] LiNi x Co y Mn 1-x-y O2+Fe 2+ +4H + =Li + +xNi 2+ +yCo 2+ +(1-xy)Mn 2+ +Fe 3+ +2H2O

[0019] LiNi a Co b Al 1-a-b O2+(a+b)Fe 2++4H + = Li + + aNi 2+ + bCo 2+ +(1 - a - b)Al 3+ +(a + b)Fe 3+ + 2H2O

[0020] cLi2MnO3·(1 - c)LiMO2+(1 + c)Fe 2+ +(4 + 2c)H + =(1 + c)Li + + cMn 2+ +(1 - c)M 2+ +(1 + c)Fe 3 + +(2 + x)H2O

[0021] Al + 3Fe 3+ = Al 3+ + 3Fe 2+

[0022] Al2O3 + 6Cl - + 6H + = 2AlCl3 + 3H2O

[0023] Based on its own variable valence characteristics, iron ions constitute a catalytic effect between the aluminum foil and the cathode active material. In addition, the role of chloride ions is to prevent the passivation of the aluminum foil in the acid solution.

[0024] Preferably, the lithium-ion battery described in step S1 is lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0.33 ≤ x ≤ 0.95, 0 < y ≤ 0.33, 0 < 1 - x - y ≤ 0.33), lithium nickel cobalt aluminate (LiNi a Co b Al 1-a-b O2, 0.8 ≤ a < 1, 0 < b ≤ 0.15, 0 < 1 - a - b ≤ 0.06), lithium-rich manganese-based (cLi2MnO3·(1 - c)LiMO2, 0 < c ≤ 0.5, M is one or more of Ni, Co, Mn, V, Al).

[0025] Lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0.33 ≤ x ≤ 0.95, 0 < y ≤ 0.33, 0 < 1 - x - y ≤ 0.33) can specifically be: LiNi 0.95 Co0.05 Mn 0.05 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2 or LiNi 0.33 Co 0.33 Mn 0.33 O2.

[0026] Lithium nickel cobalt aluminate (LiNi a Co b Al 1-a-b O2, 0.8 ≤ a < 1, 0 < b ≤ 0.15, 0 < 1 - a - b ≤ 0.06) can specifically be: LiNi 0.8 Co 0.15 Al 0.05 O2 or LiNi 0.9 Co 0.05 Al 0.05 O2.

[0027] Lithium-rich manganese-based (cLi2MnO3·(1 - c)LiMO2, 0 < c ≤ 0.5, M is one or more of Ni, Co, Mn, V, Al) can specifically be: 0.5Li2MnO3·0.5LiMn 0.3 Ni 0.4 Co 0.3 O2, 0.2Li2MnO3·0.8LiMn 0.3 Ni 0.4 Co 0.3 O2 or 0.1Li2MnO3·0.9LiMn 0.3 Ni 0.4 Co 0.3 O2.

[0028] Preferably, the maximum particle size of the cathode sheet debris in step S1 is less than 40 mm.

[0029] Preferably, the acid in step S2 is one or a mixture of hydrochloric acid, sulfuric acid, nitric acid, formic acid, and acetic acid.

[0030] Preferably, the iron-containing compound described in step S2 is one or more mixtures of iron elements or compounds containing 0 valence, +2 valence, or +3 valence, including iron elements, ferric sulfate, ferric chloride, ferric nitrate, ferrous sulfate, ferrous chloride, ferrous nitrate, ferric oxide, ferrous oxide, ferrous oxide, ferric oxide, ferric hydroxide, ferrous disulfide, ferrous sulfide and ferric sulfide. The chlorine-containing substance is a compound containing -1 valence chlorine element, including one or more mixtures of sodium chloride, potassium chloride, ferric chloride, ferrous chloride, lithium chloride, cobalt chloride, manganese dichloride, manganese tetrachloride, and nickel chloride; the iron ion concentration in the metal element-rich leachate ranges from 0.001 to 5.00 mol / L, and the chloride ion concentration ranges from 0.001 to 5.00 mol / L.

[0031] Preferably, the valuable metal in step S3 is one or more of Li, Ni, Co and Mn elements.

[0032] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0033] (1) The present invention can directly grind the positive electrode sheet and then carry out leaching, without the need for the positive electrode active material stripping process such as roasting and organic solvent dissolution in the traditional method, which significantly reduces energy consumption and pollution, improves efficiency, and has a higher metal recovery rate.

[0034] (2) The present invention introduces iron ions as a catalyst to achieve reduction leaching of the positive electrode active material by the aluminum foil current collector at room temperature, without the need to add additional expensive reducing agents, thereby reducing process costs.

[0035] (3) The present invention realizes efficient precipitation of the iron catalyst in the leachate according to the pH difference of the metal ion precipitation, obtains a high-purity valuable metal salt solution and realizes the reuse of the iron catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is the technical roadmap of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Example 1

[0039] LiNi obtained by disassembling and separating the used nickel-cobalt-manganese-oxide lithium batteries from a battery factory 0.8 Co0.1 Mn 0.1 O2 and LiNi 0.5 Co 0.2 Mn 0.3 O2 positive electrode sheet, the positive electrode sheet is crushed in a grinder for 2 minutes to obtain positive electrode sheet debris, the debris composition is Li 5.82%, Ni 36.12%, Co 8.91%, Mn 8.85%, Al 11.05%. Take 20g of positive electrode sheet debris, add 200mL of 1mol / L dilute sulfuric acid solution, and add 0.001mol of ferric hydroxide and 0.001mol of sodium chloride at the same time, stir and react for 2h at room temperature, and filter to obtain a leachate containing Li, Co, Ni, Mn, Al and Fe. Add sodium hydroxide to the leachate to adjust the pH to 5.6, and filter to obtain an iron-aluminum precipitate and a solution containing Li, Ni, Co, and Mn. Put the iron-aluminum precipitate into 1mol / L sodium hydroxide solution, stir and react for 2h, and then filter to obtain an iron hydroxide precipitate and an aluminum-containing solution. Return the iron hydroxide precipitate to the next leaching. The results showed that the leaching rates of Li, Co, Ni, Mn and Al in the acid leaching step were 99.55%, 99.12%, 99.23%, 98.93% and 99.93%, respectively.

[0040] Example 2

[0041] The LiCoO2 positive electrode sheet obtained by disassembling the waste lithium cobalt oxide battery of a battery factory was crushed in a crusher for 2 minutes to obtain debris, and the debris composition is Li 6.13%, Co 52.32%, Al 10.85%. Take 10g of positive electrode sheet debris, add 80mL of 1mol / L dilute sulfuric acid solution, and add 0.003mol ferrous chloride and 0.0001mol sodium chloride at the same time, stir and react for 2h at room temperature, and filter to obtain a leachate containing Li, Co, Al, and Fe. Sodium hydroxide is added to the leachate to adjust the pH to 5.6, and the iron-aluminum precipitate and the solution containing Li and Co are filtered. The iron-aluminum precipitate is put into 1mol / L sodium hydroxide solution, stirred and reacted for 2h, and then filtered to obtain iron hydroxide precipitate and aluminum-containing solution. The iron hydroxide precipitate is returned to the next leaching. The results showed that the leaching rates of Li, Co and Al in the acid leaching step were 99.81%, 99.72% and 99.90%, respectively.

[0042] Example 3

[0043] Waste lithium-ion battery positive plates obtained from the dismantling workshop of a battery factory, including LiCoO2 positive plates, LiNi 0.5 Co 0.2 Mn 0.3O2 positive electrode sheet and LiMn2O4 positive electrode sheet. These positive electrode sheets were crushed in a grinder for 5 minutes to obtain positive electrode sheet debris. Take 10g of positive electrode sheet debris, add 200mL of 1mol / L formic acid solution, and add 0.02moL ferric nitrate and 0.01moL potassium chloride at the same time, stir and react for 4h at room temperature, and filter to obtain a leachate containing Li, Co, Ni, Mn, Al and Fe. Add ammonia water to the leachate to adjust the pH to 5.9, and filter to obtain an iron-aluminum precipitate and a solution containing Li, Co, Ni and Mn. The iron-aluminum precipitate was put into a 1mol / L sodium hydroxide solution, stirred and reacted for 2h, and then filtered to obtain an iron hydroxide precipitate and an aluminum-containing solution. The iron hydroxide precipitate was returned to the next leaching. The leaching rates of Li, Co, Ni, Mn and Al in the acid leaching step were 99.10%, 98.59%, 99.49%, 98.23% and 99.52%, respectively.

[0044] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling waste lithium-ion battery positive plates, characterized in that: The following steps are involved: S1: Pretreatment of waste lithium-ion batteries: discharging the waste lithium-ion batteries, disassembling them to obtain positive electrode sheets, and finally crushing the positive electrode sheets to obtain positive electrode sheet fragments; S2: catalytic leaching of waste lithium-ion battery positive electrode sheets: using acid and iron-containing compounds and chlorine-containing compounds to prepare a leaching agent solution, the concentration of the leaching agent solution is 0.05-10 mol / L, adding the positive electrode sheet debris to the leaching agent solution, stirring at room temperature for 20 minutes, and filtering to obtain a leachate rich in metal elements; S3: Separating the iron and aluminum in the leachate: adding an alkaline solution to raise the pH of the leachate to 5-7 to precipitate iron and aluminum, and filtering and separating to obtain a precipitate containing iron and aluminum and a solution containing valuable metals; S4: Recycling of the catalyst: The iron-aluminum precipitate is added to an alkaline solution with a pH greater than 12 to dissolve the aluminum element, and the iron precipitate is obtained after filtration.

2. The method for recycling waste lithium-ion battery positive plates according to claim 1, characterized in that: The lithium-ion battery described in step S1 is lithium cobalt oxide LiCoO2, lithium manganese oxide LiMn2O4, lithium nickel oxide LiNiO2, lithium nickel cobalt manganese oxide LiNi x Co y Mn 1-x- y O2, where 0.33 ≤ x ≤ 0.95, 0 < y ≤ 0.33, 0 < 1 - x - y ≤ 0.33, lithium nickel cobalt aluminate LiNi a Co b Al 1-a-b O2, where 0.8 ≤ a < 1, 0 < b ≤ 0.15, 0 < 1 - a - b ≤ 0.06, lithium-rich manganese-based cLi2MnO3·(1 - c)LiMO2, where 0 < c ≤ 0.5, and M is one or more of Ni, Co, Mn, V, and Al.

3. The method for recycling waste lithium-ion battery positive electrode sheets according to claim 1, characterized in that: The maximum particle size of the positive electrode sheet debris described in step S1 is less than 40 mm.

4. The method for recycling waste lithium-ion battery positive plates according to claim 1, characterized in that: The acid described in step S2 is one or a mixed solution of hydrochloric acid, sulfuric acid, nitric acid, formic acid, and acetic acid.

5. The method for recycling waste lithium-ion battery positive plates according to claim 1, characterized in that: The iron-containing compound described in step S2 is one or more mixtures of iron elements or compounds containing 0 valence, +2 valence, or +3 valence, including iron elements, ferric sulfate, ferric chloride, ferric nitrate, ferrous sulfate, ferrous chloride, ferrous nitrate, ferric oxide, ferrous oxide, ferrous oxide, ferric oxide, ferric hydroxide, ferrous disulfide, ferrous sulfide and ferric sulfide. The chlorine-containing substance is a compound containing -1 valence chlorine element, including one or more mixtures of sodium chloride, potassium chloride, ferric chloride, ferrous chloride, lithium chloride, cobalt chloride, manganese dichloride, manganese tetrachloride, and nickel chloride; the iron ion concentration in the metal element-rich leachate ranges from 0.001 to 5.00 mol / L, and the chloride ion concentration ranges from 0.001 to 5.00 mol / L.

6. The method for recycling waste lithium-ion battery positive plates according to claim 1, characterized in that: The valuable metal in the solution containing valuable metals in step S3 is one or more of Li, Ni, Co and Mn elements.

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