Method for regenerating retired nickel-cobalt-manganese lithium acid material by electrochemical method

Abstract

The present application relates to the technical field of waste lithium ion battery recycling, recycling and the like, and discloses a method for regenerating retired nickel-cobalt-manganese lithium acid cathode material by electrochemical method, comprising the following steps: S1, electrochemical pretreatment; S2, disassembly and impurity removal; S3, solid-state sintering regeneration.The method for regenerating retired nickel-cobalt-manganese lithium acid cathode material by electrochemical method can effectively reduce the difficulty of solid-state sintering regeneration, shorten the calcination time and reduce the energy consumption.The method is simple in process and strong in operability, has high adaptability to the existing nickel-cobalt-manganese lithium acid cathode production line, and is very suitable for large-scale popularization and application.

Description

Technical Field

[0001] This technology relates to the fields of waste lithium-ion battery recycling and regeneration, specifically to an electrochemical-assisted method for regenerating retired nickel-cobalt-manganese lithium cathode materials, which overcomes the limitations of existing solid-state sintering regeneration processes, such as low lithium replenishment efficiency and poor structural repair effect. Background Technology

[0002] With its advantages of high energy density, high operating voltage, and no memory effect, lithium-ion batteries have been widely used in consumer electronics, portable devices, electric vehicles, and energy storage. Among them, lithium nickel cobalt manganese oxide layered oxide material is currently one of the mainstream cathode materials for lithium-ion batteries. Today, an increasing number of lithium-ion batteries are being retired due to reaching the end of their service life. Because they contain a large amount of metal resources with high recycling value, the recycling and regeneration of retired lithium nickel cobalt manganese oxide cathode materials has attracted much attention.

[0003] There are two main methods for recycling retired lithium nickel cobalt manganese oxide cathode materials: indirect recycling (such as pyrometallurgical and hydrometallurgical processes) and direct regeneration. Among them, the direct regeneration method can repair structural defects in situ while maintaining the integrity of the material's composition and crystal structure, rather than destroying and reforming the raw materials containing metal elements. This avoids the problems of low recycling efficiency, high energy consumption, and environmental pollution associated with traditional indirect recycling methods.

[0004] Existing direct regeneration methods for retired lithium nickel cobalt manganese oxide cathode materials mainly include solid-state sintering, molten salt method, and hydrothermal method. Among them, solid-state sintering is considered the most likely direct regeneration method to be industrialized due to its simple operation and high compatibility with existing lithium nickel cobalt manganese oxide cathode production lines.

[0005] However, the solid-state sintering regeneration method still has problems such as low lithium replenishment efficiency and poor structural repair effect. This is mainly because the surface region of the retired nickel cobalt manganese oxide cathode material has a part of spinel phase / rock salt phase structure, which not only hinders the diffusion of lithium ions in terms of kinetics and increases the difficulty of lithium replenishment, but also makes it difficult to restore the layered structure in terms of thermodynamics, thus affecting the structural repair effect. Summary of the Invention

[0006] This invention provides an electrochemical-assisted method for regenerating decommissioned lithium nickel cobalt manganese oxide (NCO) cathode materials. By performing a special electrochemical pretreatment on the decommissioned lithium-ion cells, the surface spinel / rock salt phase structure of the decommissioned NCO cathode material is eliminated. Furthermore, in-situ lithium replenishment is appropriately applied to the decommissioned NCO cathode material, thereby improving the lithium replenishment efficiency and structural repair effect of the subsequent solid-state sintering regeneration method. Currently, there are few reports of such electrochemical pretreatment processes on the market.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] An electrochemical-assisted method for regenerating decommissioned lithium nickel cobalt manganese oxide cathode materials includes the following steps:

[0009] S1. Electrochemical pretreatment.

[0010] S2, Disassembly and cleaning.

[0011] S3, solid-state sintering regeneration.

[0012] Furthermore, the electrochemical pretreatment in step S1 includes the following steps: charging the retired lithium-ion cell at a low current density to an ultra-high upper limit voltage and maintaining constant voltage charging for a certain period of time, then discharging it at a low current density to an ultra-low lower limit voltage and maintaining constant voltage discharge for a certain period of time.

[0013] Furthermore, the retired lithium-ion battery cell refers to a lithium-ion battery cell that uses lithium nickel cobalt manganese oxide layered oxide material as the positive electrode, and the chemical formula of lithium nickel cobalt manganese oxide layered oxide material is LiNi. x Co y Mn z O2(x+y+z=1).

[0014] Furthermore, the low current density is a current density of 0.1C-0.5C calculated based on lithium nickel cobalt manganese oxide cathode material.

[0015] Furthermore, the ultra-high upper limit voltage is 4.8-5.0 V calculated per individual cell (vs. Li / Li). + ).

[0016] Furthermore, the constant voltage charging duration is 1-15 hours.

[0017] Furthermore, the ultra-low voltage limit is 1.0-1.5 V calculated per individual cell (vs. Li / Li). + ).

[0018] Furthermore, the constant voltage discharge is maintained for 1-15 hours.

[0019] Furthermore, the disassembly and impurity removal in step S2 includes the following steps: disassembling the retired lithium-ion battery cell under safe conditions to obtain the retired lithium nickel cobalt manganese oxide positive electrode sheet, and then removing impurities including current collectors and binders to obtain retired lithium nickel cobalt manganese oxide positive electrode material powder.

[0020] Further, the solid-state sintering regeneration in step S3 includes the following steps: determining the proportion of Li, Ni, Co, and Mn elements in the retired lithium nickel cobalt manganese oxide cathode material powder, mixing the supplemented lithium salt and transition metal salt with the retired lithium nickel cobalt manganese oxide cathode material powder according to the stoichiometric ratio of the target product, and then performing solid-state sintering to obtain the regenerated lithium nickel cobalt manganese oxide cathode material.

[0021] Compared with existing solid-state sintering regeneration methods, this invention achieves the following technical advantages:

[0022] (1) The electrochemical-assisted regeneration method for retired lithium nickel cobalt manganese oxide cathode materials provided by the present invention can significantly improve the lithium replenishment efficiency and structural repair effect of the subsequent solid-state sintering regeneration process by electrochemically etching the surface spinel phase / rock salt phase structure of the retired lithium nickel cobalt manganese oxide cathode material through a constant voltage charging process with an ultra-high upper limit voltage.

[0023] (2) The electrochemical-assisted method for regenerating retired lithium nickel cobalt manganese oxide cathode materials provided by the present invention can perform deep in-situ lithium replenishment on retired lithium nickel cobalt manganese oxide cathode materials through a constant voltage discharge process at an ultra-low lower limit voltage, making full use of the residual lithium elements on the negative electrode side, while facilitating the safe disassembly of subsequent lithium-ion cells.

[0024] (3) The electrochemical-assisted regeneration method for retired lithium nickel cobalt manganese oxide cathode materials provided by the present invention can reduce the difficulty of solid-state sintering regeneration, shorten the calcination time, and reduce energy consumption.

[0025] (4) The electrochemical-assisted regeneration method for retired lithium nickel cobalt manganese oxide cathode materials provided by the present invention is simple, highly operable, and highly compatible with existing lithium nickel cobalt manganese oxide cathode production lines, making it suitable for large-scale application. Attached Figure Description

[0026] Figure 1 The first charge-discharge curves of the recycled NCM811 cathode material in the examples and comparative examples are shown at 0.1C and 3.0-4.3V.

[0027] Figure 2 The images show the XRD test results of the recycled NCM811 cathode material in the examples and comparative examples. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative and explanatory and do not limit the scope of protection of this invention.

[0029] This invention provides a method for electrochemical-assisted regeneration of decommissioned lithium nickel cobalt manganese oxide cathode materials, comprising the following steps:

[0030] S1. Electrochemical pretreatment: First, the retired lithium-ion battery cell is charged at a constant current at a low current density to the ultra-high upper limit voltage and kept at a constant voltage for a certain period of time. Then, it is discharged at a constant current at a low current density to the ultra-low lower limit voltage and kept at a constant voltage for a certain period of time.

[0031] S2. Disassembly and impurity removal: Under safe conditions, disassemble the retired lithium-ion battery cell to obtain the retired lithium nickel cobalt manganese oxide positive electrode sheet, and then remove impurities such as current collector and binder to obtain retired lithium nickel cobalt manganese oxide positive electrode material powder.

[0032] S3. Solid-state sintering regeneration: The proportions of elements such as Li, Ni, Co, and Mn in the retired lithium nickel cobalt manganese oxide cathode material powder are determined. The supplemented lithium salt and transition metal salt are mixed with the retired lithium nickel cobalt manganese oxide cathode material powder at high speed according to the stoichiometric ratio of the target product, and then solid-state sintering is performed to obtain the regenerated lithium nickel cobalt manganese oxide cathode material.

[0033] In step S1, the retired lithium-ion battery cell refers to a lithium-ion battery cell that uses lithium nickel cobalt manganese oxide layered oxide material as the positive electrode. The chemical formula of lithium nickel cobalt manganese oxide layered oxide material is LiNi. x Co y Mn z O2(x+y+z=1).

[0034] In step S1, the low current density is the current density of 0.1C-0.5C calculated based on lithium nickel cobalt manganese oxide cathode material.

[0035] In step S1, the ultra-high upper limit voltage is 4.8-5.0 V calculated per individual cell (vs. Li / Li). + The constant voltage charging time is 1-15 hours.

[0036] In step S1, the ultra-low lower limit voltage is 1.0-1.5 V calculated per individual cell (vs. Li / Li). + The constant voltage discharge duration is 1-15 h.

[0037] To make the present invention more fully disclosed, more specific embodiments are described below.

[0038] Example 1

[0039] An electrochemical method for assisting the decommissioning of LiNi 0.8 Co 0.1 Mn 0.1 The method for regenerating O2 (NCM811) cathode material includes the following steps:

[0040] S1. Electrochemical pretreatment: First, the retired lithium-ion battery cell is constant-current charged to 4.9 V (vs. Li / Li) at a current density of 0.1C. + ), and maintain 4.9 V (vs. Li / Li) + Constant voltage charging for 5 hours, followed by constant current discharging at a current density of 0.1C to 1.2V (vs. Li / Li). + ), and maintain 1.2 V (vs. Li / Li)+ Constant voltage discharge for 10 hours.

[0041] S2. Disassembly and impurity removal: Under safe conditions, disassemble the retired lithium-ion battery cell to obtain the retired NCM811 positive electrode sheet, and then remove impurities such as current collector and binder to obtain retired NCM811 positive electrode material powder.

[0042] S3. Solid-state sintering regeneration: The proportions of elements such as Li, Ni, Co, and Mn in the retired NCM811 cathode material powder were determined. According to the stoichiometric ratio of the target product NCM811, the supplemented LiOH, LiNO3, nickel acetate / cobalt acetate / manganese acetate were mixed with the retired NCM811 cathode material powder by high-speed ball milling at 2000 rpm. Then, solid-state sintering was carried out under pure oxygen atmosphere at a heating rate of 2℃ / min. The mixture was first calcined at 480℃ for 2 h, and then calcined at 770℃ for 4 h. After natural cooling to room temperature, the regenerated NCM811 cathode material was obtained.

[0043] Comparative Example 1

[0044] A retired LiNi 0.8 Co 0.1 Mn 0.1 The method for regenerating O2 (NCM811) cathode material includes the following steps:

[0045] S1. Disassembly and impurity removal: Under safe conditions, disassemble the retired lithium-ion battery cell to obtain the retired NCM811 positive electrode sheet, and then remove impurities such as current collector and binder to obtain retired NCM811 positive electrode material powder.

[0046] S2. Solid-state sintering regeneration: The proportions of elements such as Li, Ni, Co, and Mn in the retired NCM811 cathode material powder were determined. According to the stoichiometric ratio of the target product NCM811, the supplemented LiOH, LiNO3, nickel acetate / cobalt acetate / manganese acetate were mixed with the retired NCM811 cathode material powder by high-speed ball milling at 2000 rpm. Then, solid-state sintering was carried out under pure oxygen atmosphere at a heating rate of 2℃ / min. The mixture was first calcined at 480℃ for 2 h, and then calcined at 770℃ for 4 h. After natural cooling to room temperature, the regenerated NCM811 cathode material was obtained.

[0047] Table 1. Electrochemical performance test results of the recycled NCM811 cathode materials in the examples and comparative examples.

[0048]

[0049] From Table 1 and Figure 1It can be seen that after adopting the electrochemical pretreatment process provided by the present invention, the first-cycle discharge specific capacity and first-cycle coulombic efficiency of the regenerated NCM811 cathode material in the embodiment are significantly improved, which are far superior to the regenerated NCM811 cathode material in the comparative example, and can meet the usage standards of commercial NCM811 cathode materials.

[0050] from Figure 2 It can be seen that the intensity ratio of the (003) and (104) diffraction peaks of the regenerated NCM811 cathode material in the embodiment is 1.33, which is significantly higher than the 1.09 of the comparative example. This indicates that after using the electrochemical pretreatment process provided by the present invention, the layered structure of the regenerated NCM811 cathode material is well repaired and the degree of lithium-nickel mixing is reduced.

Claims

1. A method for electrochemically assisted regeneration of retired nickel-cobalt-manganese lithium cathode material, characterized in that, Comprise the following steps: S1, electrochemical pretreatment retired lithium-ion battery cell is charged at a low current density to an ultra-high upper limit voltage and maintained at constant voltage for a certain time, and then discharged at a low current density to an ultra-low lower limit voltage and maintained at constant voltage for a certain time, the low current density being a current density of 0.1C-0.5C rate calculated based on the nickel-cobalt-manganese lithium cathode material, the ultra-high upper limit voltage being 4.8-5.0 V vs. Li / Li + , calculated based on the single cell, and the ultra-low lower limit voltage being 1.0-1.5 V vs. Li / Li + ; S2, disassembly and impurity removal Disassembling the retired lithium ion battery under safe conditions to obtain the retired lithium nickel cobalt manganese oxide positive electrode sheet, and then removing the impurities including the current collector and the binder to obtain the retired lithium nickel cobalt manganese oxide positive electrode material powder; S3, solid state sintering regeneration Determining the proportion of Li, Ni, Co and Mn elements in the retired lithium nickel cobalt manganese oxide positive electrode material powder, mixing the supplemented lithium salt and transition metal salt with the retired lithium nickel cobalt manganese oxide positive electrode material powder according to the stoichiometric ratio of the target product, and then performing solid state sintering to obtain the regenerated lithium nickel cobalt manganese oxide positive electrode material.

2. The method for regenerating the retired Li-NMC positive electrode material assisted by electrochemical method according to claim 1, characterized in that, The retired lithium-ion battery cell refers to a lithium-ion battery cell with a lithium nickel cobalt manganese oxide layered oxide material as a positive electrode, and the chemical formula of the lithium nickel cobalt manganese oxide layered oxide material is LiNi x Co y Mn z O2, wherein x+y+z=1.

3. The method for regenerating the retired Li-NMC positive electrode material assisted by electrochemical method according to claim 1, characterized in that, The holding time of constant voltage charging is 1-15 h.

4. The method for regenerating the retired Li-NMC positive electrode material assisted by electrochemical method according to claim 1, characterized in that, The holding time of constant voltage discharging is 1-15 h.

Images