Method for supercritical recovery of cobalt from waste lithium ion batteries

Abstract

A method for recovering cobalt from waste lithium ion batteries by supercritical method, comprising the following steps: disassembling the waste batteries to separate the positive electrode; using a supercritical water / ethanol system to leach the positive electrode to obtain a cobalt-rich leaching residue; and using sulfuric acid to leach the cobalt-rich leaching residue to obtain a cobalt sulfate solution after filtration. Compared with traditional fire and wet methods, the method for recovering cobalt by supercritical method avoids multiple strong acid or strong base leaching, avoids the generation of a large amount of waste gas and waste liquid, has a simple process, fast reaction speed, and does not require a catalyst due to the reaction in a supercritical system, thereby reducing costs and subsequent separation process steps, and also reducing side reactions caused by the catalyst. The method realizes pollution-free, high-purity and high-recovery-rate recycling of waste lithium ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling, and more particularly to a method for recycling lithium cobalt oxide batteries. Background Technology

[0002] Lithium-ion batteries are a core component of new energy vehicles, and with the rapid development of new energy vehicles, the number of lithium-ion batteries in use has increased rapidly. At the same time, the recycling of used lithium-ion batteries has received widespread attention, especially the recycling of used ternary lithium-ion batteries, which has propelled the resource utilization of used ternary lithium-ion batteries into a fast track of development.

[0003] Lithium cobalt oxide was the first commercially available cathode material for lithium-ion batteries due to its high true density of 5.1 g / cm³. 3 Compacted density 4.2 g / cm³ 3 Its high discharge voltage (4.5V) and good doping properties have led to its widespread application.

[0004] Currently, the main methods for recycling valuable metals from spent lithium-ion batteries are hydrometallurgical and pyrometallurgical processes. Hydrometallurgical processes typically involve acid or alkali leaching of the cathode material, followed by multi-stage extraction, precipitation, and filtration to obtain a single metal product. However, hydrometallurgical processes generate large volumes of wastewater and have high treatment costs, limiting their application. Pyrometallurgical processes have lower requirements for raw materials and can process large quantities of spent battery materials to obtain metal mixtures or alloys. However, pyrometallurgical processes are energy-intensive and generate large amounts of waste gas. Furthermore, both traditional hydrometallurgical and pyrometallurgical processes struggle to remove binders from spent battery materials. Since cathode materials are usually composed of multiple components, PVDF and NMP are commonly used as binders during preparation, and these binders exhibit strong stability. Therefore, the recovery rate and purity of the metals cannot be guaranteed using traditional pyrometallurgical and hydrometallurgical processes. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system. The recovery process is simple, efficient, low-cost, and pollution-free, achieving high-purity and high-recovery-rate recovery of cobalt.

[0006] A method for supercritical recycling of cobalt from spent lithium-ion batteries includes the following steps:

[0007] Disassemble used batteries and separate the positive electrode;

[0008] The cathode was leached using a supercritical water / ethanol system to obtain a cobalt-rich leaching residue.

[0009] This invention involves dismantling used batteries to separate the positive electrode, which is then leached using a supercritical water / ethanol system. Under supercritical conditions, the supercritical water / ethanol system exhibits strong oxidizing properties and good solubility for organic matter; simultaneously, the ethanol in this system also strongly oxidizes under supercritical conditions. The positive electrode material also contains a binder, primarily composed of PVDF and NMP, which can be dissolved and oxidized in the supercritical water / ethanol system. After cooling and depressurizing the system to room temperature and pressure, a lithium-rich leachate and a cobalt-rich leachate residue are obtained.

[0010] As a preferred embodiment, the supercritical water / ethanol system comprises water, ethanol, and additives. Experiments revealed that adding a small amount of additives significantly improves leaching efficiency while reducing leaching temperature and pressure, leaching time, and energy consumption.

[0011] As a preferred option, the auxiliary agent is at least one of ketone and ether, both of which are readily soluble in supercritical water / ethanol systems.

[0012] As a preferred embodiment, the ketone is a C3-C6 ketone and the ether is a C3-C8 ether. Short-chain ketones and ethers are readily available and are liquid at room temperature. More preferably, butanone is the most effective auxiliary agent in this system.

[0013] As a preferred embodiment, the liquid-to-solid ratio (ml:g) of the supercritical water / ethanol system to the positive electrode is (5-25):1. A liquid-to-solid ratio that is too low may result in incomplete leaching, while a liquid-to-solid ratio that is too high will increase energy consumption.

[0014] As a preferred embodiment, in the supercritical water / ethanol system, the volume ratio of water, ethanol and additives is 100:(5-15):(0.1-1). Too low a content of ethanol and additives may reduce the leaching efficiency, while too high a content will increase the cost.

[0015] As a preferred embodiment, the temperature of the supercritical water / ethanol system is 375-550℃ and the pressure is 22.1-40MPa. Too low a temperature and pressure may result in incomplete leaching, and the binder may also remain in the leachate and leaching residue. Too high a liquid-to-solid ratio will increase energy consumption.

[0016] As a preferred option, the immersion time is 1-6 hours. Too short an immersion time may result in incomplete immersion, while too long an immersion time will increase energy consumption.

[0017] As a preferred option, the waste lithium-ion battery is a lithium cobalt oxide battery, and treating waste lithium cobalt oxide batteries in a supercritical water / ethanol system has a better cobalt recovery rate.

[0018] As a preferred option, the cobalt-rich leaching residue is leached with sulfuric acid, and the resulting cobalt sulfate solution is obtained after filtration. The cobalt sulfate solution can be directly used in subsequent production.

[0019] This invention utilizes a supercritical water / ethanol system to leach the cathode material of spent lithium-ion batteries. The binder in the cathode material is dissolved and oxidized for removal, and the lithium cobalt oxide (LiCO) and lithium are separated from the cathode material, yielding a cobalt-rich leaching residue and a lithium-rich leachate, thus achieving the separation and recovery of cobalt from the cathode material. Compared to traditional pyrometallurgical and hydrometallurgical methods, this supercritical cobalt recovery method avoids multiple strong acid or alkali leaching processes, and also avoids the generation of large amounts of waste gas and waste liquid. The process is simple and the reaction speed is fast. Moreover, because the reaction occurs in a supercritical system, no catalyst is required, reducing costs and subsequent separation process steps, while also reducing side reactions caused by catalysts. This achieves pollution-free, high-purity, and high-recovery-rate recycling of spent lithium-ion batteries. Detailed Implementation

[0020] The present invention discloses a method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system, comprising the following steps:

[0021] Disassemble used batteries and separate the positive electrode;

[0022] The positive electrode is leached using a supercritical water / ethanol system, wherein the liquid-to-solid ratio (ml:g) of the supercritical water / ethanol system to the positive electrode is (5-25):1; the temperature of the supercritical water / ethanol system is 375-550℃, the pressure is 22.1-40MPa, and the leaching time is 1-6h; the supercritical water / ethanol system also includes an auxiliary agent, wherein the volume ratio of water, ethanol, and the auxiliary agent is 100:(5-15):(0.1-1), and the auxiliary agent is at least one of a C3-C6 ketone or a C3-C8 ether. After leaching, a cobalt-rich leaching residue is obtained. This residue is then acid-leached with sulfuric acid, and the resulting solution is obtained after filtration.

[0023] Example 1

[0024] A method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system includes the following steps:

[0025] Disassemble used batteries and separate the positive electrode;

[0026] The positive electrode was leached using a supercritical water / ethanol system, with a liquid-to-solid ratio (ml:g) of 10:1. The supercritical water / ethanol system was leached at 400°C and 23 MPa for 3 hours. The supercritical water / ethanol system also included an auxiliary agent, with a volume ratio of water, ethanol, and the auxiliary agent of 100:6:0.5. The auxiliary agent was methyl ethyl ketone (MEK). After leaching, a cobalt-rich leaching residue was obtained. This residue was then acid-leached with sulfuric acid, and the resulting solution was filtered to obtain a cobalt sulfate solution.

[0027] The cobalt-rich leaching residue contains less than 0.5% binder residue, and the cobalt sulfate solution has a cobalt recovery rate of greater than 99%.

[0028] Example 2

[0029] A method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system includes the following steps:

[0030] Disassemble used batteries and separate the positive electrode;

[0031] The positive electrode was leached using a supercritical water / ethanol system, with a liquid-to-solid ratio (ml:g) of 5:1. The supercritical water / ethanol system was leached at 550°C and 40 MPa for 1 hour. The supercritical water / ethanol system also included an auxiliary agent, with a volume ratio of water, ethanol, and the auxiliary agent of 100:5:0.1. The auxiliary agent was methyl ethyl ketone (MEK). After leaching, a cobalt-rich leaching residue was obtained. This residue was then acid-leached with sulfuric acid, and the resulting solution was filtered to obtain a cobalt sulfate solution.

[0032] The cobalt-rich leaching residue has a binder residue of less than 0.2%, and the cobalt recovery rate in the cobalt sulfate solution is greater than 99%.

[0033] Example 3

[0034] A method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system includes the following steps:

[0035] Disassemble used batteries and separate the positive electrode;

[0036] The positive electrode was leached using a supercritical water / ethanol system, with a liquid-to-solid ratio (ml:g) of 25:1. The supercritical water / ethanol system was leached at 375°C and 22.1 MPa for 6 hours. The supercritical water / ethanol system also included an auxiliary agent, with a volume ratio of water, ethanol, and the auxiliary agent of 100:15:1. The auxiliary agent was methyl ethyl ketone (MEK). After leaching, a cobalt-rich leaching residue was obtained. This residue was then acid-leached with sulfuric acid, and the resulting solution was filtered to obtain a cobalt sulfate solution.

[0037] The cobalt-rich leaching residue contains less than 0.5% binder residue, and the cobalt sulfate solution has a cobalt recovery rate of greater than 99%.

[0038] Example 4

[0039] A method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system includes the following steps:

[0040] Disassemble used batteries and separate the positive electrode;

[0041] The positive electrode was leached using a supercritical water / ethanol system, with a liquid-to-solid ratio (ml:g) of 15:1. The supercritical water / ethanol system was leached at 480°C and 30 MPa for 2 hours. The supercritical water / ethanol system also included an auxiliary agent, with a volume ratio of water, ethanol, and the auxiliary agent of 100:8:0.3. The auxiliary agent was acetone. After leaching, a cobalt-rich leaching residue was obtained. This residue was then acid-leached with sulfuric acid, and the resulting solution was filtered to obtain a cobalt sulfate solution.

[0042] The cobalt-rich leaching residue has a binder residue of less than 0.7%, and the cobalt recovery rate in the cobalt sulfate solution is greater than 99%.

[0043] Example 5

[0044] A method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system includes the following steps:

[0045] Disassemble used batteries and separate the positive electrode;

[0046] The positive electrode was leached using a supercritical water / ethanol system, with a liquid-to-solid ratio (ml:g) of 15:1. The supercritical water / ethanol system was leached at 400°C and 25 MPa for 2 hours. The supercritical water / ethanol system also included an auxiliary agent, with a volume ratio of water, ethanol, and the auxiliary agent of 100:10:0.6. The auxiliary agent was tetrahydrofuran. After leaching, a cobalt-rich leaching residue was obtained. This residue was then acid-leached with sulfuric acid, and the resulting solution was filtered to obtain a cobalt sulfate solution.

[0047] The cobalt-rich leaching residue has a binder residue of less than 0.6%, and the cobalt recovery rate in the cobalt sulfate solution is greater than 99%.

[0048] Example 6

[0049] A method for recovering cobalt from lithium cobalt oxide batteries using a supercritical water / ethanol system includes the following steps:

[0050] Disassemble used batteries and separate the positive electrode;

[0051] The positive electrode was leached using a supercritical water / ethanol system, with a liquid-to-solid ratio (ml:g) of 10:1. The supercritical water / ethanol system was leached at 400°C and 25 MPa for 2 hours. The supercritical water / ethanol system also included an additive, with a volume ratio of water, ethanol, and the additive being 100:10:0.5. The additive was 1,4-dioxane. After leaching, a cobalt-rich leaching residue was obtained. This residue was then acid-leached with sulfuric acid, and the resulting solution was filtered to obtain a cobalt sulfate solution.

[0052] The cobalt-rich leaching residue has a binder residue of less than 0.6%, and the cobalt recovery rate in the cobalt sulfate solution is greater than 99%.

[0053] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for supercritical cobalt recovery from spent lithium-ion batteries, characterized in that, The method comprises the following steps: The spent lithium-ion battery is disassembled to separate the positive electrode; The positive electrode is leached in a supercritical water / ethanol system to obtain a cobalt-rich leaching residue; The liquid-solid ratio of the supercritical water / ethanol system to the positive electrode is 5-25 ml:1 g; The supercritical water / ethanol system is a mixed system of water, ethanol and butanone, wherein the volume ratio of the water, ethanol and butanone is 100:5-15:0.1-1; The temperature of the supercritical water / ethanol system is 375-550 DEG C, and the pressure is 22.1-40 MPa; The spent lithium-ion battery is a lithium cobaltate battery.

2. The method for recovering cobalt from waste lithium-ion batteries in a supercritical state according to claim 1, characterized in that, The leaching time is 1-6 h.

3. The method according to claim 1, further comprising the following feature: the cobalt-rich leaching residue is acid leached with sulfuric acid to obtain a cobalt sulfate solution after filtration.