Method for promoting pre-lithiation of waste electrode material

Abstract

The application relates to the technical field of lithium batteries and discloses a method for promoting pre-lithiation of waste electrode materials, which comprises the following steps: mixing waste electrode materials and lithium salt and then performing ball milling treatment to obtain primary pre-lithiation materials; and performing washing, centrifugation and drying on the primary pre-lithiation materials to obtain pre-lithiation materials rich in oxygen defects. The application promotes pre-lithiation of the waste electrode materials by regulating the generation of oxygen defects on the surface of waste ternary positive electrode materials in a mechanical activation process and further adding lithium salt in the mechanical activation process, the process makes the surface of the waste positive electrode materials generate rich oxygen defects, promotes pre-embedding of part of lithium ions into the crystal lattice of the electrode materials, increases the lithium content in the electrode materials, and realizes pre-lithiation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a method for promoting pre-intercalation of lithium in waste electrode materials. BACKGROUND

[0002] Under the driving of ecological, social and economic factors, the field of battery recycling has made significant progress in recent years, especially the innovative direct regeneration strategy can be an ideal method to repair degraded positive electrode materials without destroying the materials. Compared with traditional metallurgical methods, the direct regeneration strategy shows significant advantages. With the reduction of closed-loop production cost and the reduction of pollution emissions, direct lithium supplementation has become a hot research topic, but previous research often ignores the structural characteristics of the material itself. SUMMARY

[0003] Therefore, the present application provides a method for promoting pre-intercalation of lithium in waste electrode materials, which utilizes the structural characteristics of the material itself to induce oxygen defects on the surface of the waste electrode material through a mechanical activation process, while a pre-intercalation reaction occurs.

[0004] In order to achieve the above purpose, the following technical solutions are adopted:

[0005] In one aspect, the present application provides a method for promoting pre-intercalation of lithium in waste electrode materials, comprising the following steps:

[0006] (1) mixing the waste electrode material and lithium salt and then performing ball milling treatment to obtain a preliminary pre-intercalation lithium material;

[0007] (2) washing, centrifuging and drying the preliminary pre-intercalation lithium material to obtain a pre-intercalation lithium material rich in oxygen defects.

[0008] Preferably, the rotation speed of the ball milling treatment is 300-500 rpm, the duration is 4-14 h, and the ball-to-material ratio is (22-27):1.

[0009] Preferably, the lithium salt includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate.

[0010] Preferably, the molar ratio of lithium in the lithium salt to transition metal elements in the waste electrode material is (1-1.1):1.

[0011] Preferably, the washing is repeated 3-5 times with 60-80℃ water and then repeated 1-3 times with anhydrous ethanol.

[0012] Preferably, the centrifugation speed is 8500-11000 rpm and the time is 5-10 min.

[0013] Preferably, the drying is drying at 50-80 DEG C for 6-12 h in an air atmosphere.

[0014] Preferably, the waste electrode material is from waste lithium batteries, and the waste lithium batteries include nickel-cobalt-manganese ternary lithium batteries in different proportions.

[0015] In another aspect, the present application also provides a pre-lithiation material rich in oxygen defects, which is obtained by the method for promoting pre-lithiation of waste electrode material according to any one of the above.

[0016] The present application provides a method for promoting pre-lithiation of waste electrode material, which has the beneficial effects compared with the prior art in that:

[0017] In the mechanical activation process, the mechanical force induces the formation of oxygen defects on the surface of the waste electrode material, and lithium salt is added in the process to promote the pre-lithiation of the waste electrode material. The method of the present application mainly uses common and low-cost industrial raw materials such as deionized water and anhydrous ethanol, and only mechanical activation is required in the operation process, without adding any other additives in the process. Therefore, the method of the present application is easy to implement in industrial production, and has strong potential for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0019] Figure 1 EPR spectra of samples obtained after mechanical activation for different times in Example 1;

[0020] Figure 2 XPS O1s spectra of materials after mechanical activation and pre-lithiation in Examples 2-8;

[0021] Figure 3 Peak area fitting results of XPS O1s spectra of materials after mechanical activation and pre-lithiation in Examples 2-8;

[0022] Figure 4 XPS C1s spectra of materials after mechanical activation and pre-lithiation in Examples 2-8;

[0023] Figure 5 XPS Li 1s spectra of materials after mechanical activation and pre-lithiation in Examples 2-8;

[0024] Figure 6The lithium content test results of the repeatedly washed mechanically activated pre-lithiated material in Examples 2-8. DETAILED DESCRIPTION

[0025] The present application will be described in detail below with specific examples, and it will be understood by those skilled in the art that the specific examples below are only for illustrative purposes, and do not limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the reagents and equipment used are commercially available. If the specific processing conditions and methods are not explicitly described in the following examples, the conditions and methods known in the art can be used for processing.

[0026] In one aspect of the present application, the present application proposes a method for promoting pre-lithiation of waste electrode material, comprising the following steps:

[0027] Step S100. The waste electrode material and lithium salt are mixed and subjected to ball milling treatment to obtain a preliminary pre-lithiated material.

[0028] In this step, the waste electrode material comes from waste lithium batteries, and the waste lithium batteries include different proportions of nickel-cobalt-manganese ternary lithium batteries, such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2 or LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0029] The rotation speed of the ball milling treatment is 300-500 rpm, preferably 350-450 rpm, and the duration is 4-14 h, preferably 8-10 h, and the ball-to-material ratio is (22-27): 1, preferably (24-25): 1. By mechanically activating the waste electrode material through ball milling, the generation of oxygen defects is induced. Under the above ball milling treatment parameters, the optimal pre-lithiation reaction conditions can be determined. If the rotation speed is too high, the lithium salt raw material will be lost, and if the ball milling time is too long, the pre-lithiation content in the material will decrease.

[0030] The lithium salt includes one or more of lithium hydroxide, lithium carbonate, and lithium nitrate, and is preferably lithium hydroxide. By adding lithium salt during mechanical activation, the decomposition of lithium salt is induced, and the pre-lithiation of waste electrode material is promoted.

[0031] The molar ratio of lithium element in the lithium salt to transition metal element in the waste electrode material is (1-1.1):1, preferably 1.05:1.

[0032] The present application initiates the formation of oxygen vacancies through the mechanical activation process, and successfully realizes the pre-lithiation of the material by adding lithium salt in the mechanical activation process, and promotes the replenishment of lattice lithium in the waste material.

[0033] Step S200. The preliminary pre-lithiation material is washed, centrifuged and dried to obtain a pre-lithiation material rich in oxygen defects.

[0034] In this step, the washing is: repeatedly washing 3-5 times with 60-80℃ water, and then repeatedly washing 1-3 times with anhydrous ethanol, which can remove the unreacted residual lithium salt; the centrifugal speed is 8500-11000rpm, and the time is 5-10min; the drying is: drying at 50-80℃ in air atmosphere for 6-12h.

[0035] On the other hand, the present application also provides a pre-lithiation material rich in oxygen defects, which is obtained by the above-mentioned method for promoting the pre-lithiation of the waste electrode material, and the lithium content in the pre-lithiation material is increased by 8-11%.

[0036] The process for determining the lithium content in the pre-lithiation material is as follows: the pre-lithiation material is dissolved with aqua regia, and then distilled water is used to dilute to 1L, and then the lithium content in the pre-lithiation material is determined by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0037] In order to further illustrate the present application, the technical solutions provided by the present application will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0038] Example 1

[0039] The waste ternary positive electrode material LiNi 0.5 Co 0.2 Mn 0.3 O2 is calcined in air atmosphere to obtain a waste electrode material without binder and carbon black.

[0040] 1g of waste material is put into a 100mL ball mill tank, the ball-to-material ratio is 25:1, and mechanical activation is carried out at a speed of 360rpm for 8h, and sampling is carried out before and after 4h of mechanical activation, and named as MA-0h, MA-4h and MA-8h, respectively, and EPR test is carried out.

[0041] Example 2

[0042] Put 1 g of waste material into a 100 mL ball mill jar, add lithium hydroxide monohydrate, the stoichiometric ratio is 1.05:1 according to lithium and transition metal elements, the ball-to-material ratio is 25:1, and mechanical activation is carried out at a rotation speed of 360 rpm for 2 h to obtain a pre-lithiated material for 2 h, and XPS testing is carried out; then, 5 times of washing are carried out using deionized water at 60°C, 2 times of washing are carried out using anhydrous ethanol, and high-speed centrifugation is carried out at a rotation speed of 10,000 rpm for 8 min, and drying is carried out at 65°C in an air atmosphere for 10 h; aqua regia is used for dissolution, and ICP-OES testing is carried out to determine the lithium content of the pre-lithiated material.

[0043] Example 3

[0044] The difference between this example and Example 2 is only that the mechanical activation time is 4 h, and the remaining operation steps are the same as those of Example 2.

[0045] Example 4

[0046] The difference between this example and Example 2 is only that the mechanical activation time is 6 h, and the remaining operation steps are the same as those of Example 2.

[0047] Example 5

[0048] The difference between this example and Example 2 is only that the mechanical activation time is 8 h, and the remaining operation steps are the same as those of Example 2.

[0049] Example 6

[0050] The difference between this example and Example 2 is only that the mechanical activation time is 10 h, and the remaining operation steps are the same as those of Example 2.

[0051] Example 7

[0052] The difference between this example and Example 2 is only that the mechanical activation time is 12 h, and the remaining operation steps are the same as those of Example 2.

[0053] Example 8

[0054] The difference between this example and Example 2 is only that the mechanical activation time is 14 h, and the remaining operation steps are the same as those of Example 2.

[0055] The waste electrode material is subjected to 8 h of mechanical activation treatment (MA-8h), and samples are taken before the reaction starts (MA-0h) and when the reaction is carried out for 4 h (MA-4h) for electron paramagnetic resonance (EPR) testing, and the results are as follows: Figure 1As shown in the figure, a typical EPR signal was detected in all samples, centered at g = 2.003, indicating that electrons are trapped in oxygen vacancies, and the generation of oxygen vacancies enhances the signal peak. The figure shows that the signal peak significantly strengthens with increasing reaction time, indicating a significant increase in the oxygen defect content on the electrode material surface during mechanical activation.

[0056] This invention uses X-ray photoelectron spectroscopy (XPS) to analyze the changes in the chemical environment of the sample elements during the mechanical activation process, based on the unwashed materials after mechanical activation and pre-lithiation in Examples 2-8. The 1s spectra are shown below. Figure 2 The peak area fitting results are shown in Figure 3 C 1s energy spectrum can be found Figure 4 The Li 1s energy spectrum is shown in Figure 5 In the O1s spectrum, the corresponding impurity oxygen (O) was obtained by fitting. Impurity 531.4 eV) and lattice oxygen (O Lattice The characteristic peaks at 529.4 eV and at 530.8 eV belong to oxygen vacancies (O2) in the material. Vacancy The peaks of the O 1s spectrum showed that the oxygen defect characteristic peaks continuously increased during mechanical activation, indicating that mechanical force simultaneously induced the formation of oxygen vacancies in the NCM material; the O 1s spectrum represents surface lithium salt impurities. Impurity Gradually decrease, O Vacancy The continuously increasing intensity indicates that not only significant lithium source decomposition and pre-lithiation reactions occurred during mechanical activation, but also the generation of surface oxygen vacancies was induced. The C 1s spectrum at 289.8 eV shows CO32-. 2- The characteristic peaks of this phenomenon are the main products of the reaction between LiOH·H2O and CO2 in the air. Therefore, changes in the content of LiOH·H2O can be observed through CO3. 2- The relative content was used to infer the lithium content. The Li 1s spectrum showed a characteristic peak of Li-O bonds in the NCM cathode material at 54.25 eV, and the peak at 55.25 eV belonged to Li-O- in Li₂CO₃ / LiOH; while a characteristic peak belonging to LiF was detected at 56.2 eV. The test results show that as the mechanical activation reaction time increases, the characteristic peaks belonging to the lithium salt phase gradually weaken, accompanied by an enhancement of the lattice lithium characteristic peaks, indicating that the mechanical activation process does indeed induce some lithium to enter the lattice.

[0057] ICP-OES tests were performed on the materials from Examples 2-8 after mechanical activation and pre-lithiation, followed by washing and drying. The results are shown in [Figure Number]. Figure 6After 2h of reaction, the molar ratio of lithium in the material increased significantly from 0.844 to 0.875 and continued to increase during 2h to 10h, and then decreased slightly, which indicated that the mechanical activation process successfully induced the decomposition of part of LiOH and pre-embedded part of lithium into the positive electrode material, directly proved the occurrence of pre-embedded lithium process, after 10h of mechanical activation, the change of each component tended to be stable, which indicated that the pre-embedded lithium reaction was completed during this period, and the lithium content increased by about 11%.

[0058] In summary, the present application controls the generation of oxygen defects on the surface of waste ternary positive electrode material by mechanical activation process, and further adds lithium salt in the mechanical activation process to promote the pre-embedded lithium of waste electrode material, the process makes the surface of waste positive electrode material generate rich oxygen defects, and promotes part of lithium ions to be pre-embedded into the crystal lattice of electrode material, increases the lithium content in the electrode material, and realizes the pre-embedded lithium.

[0059] Although the embodiments of the present application have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the present application.

Claims

1. A method for promoting pre-lithiation of a spent electrode material, the method comprising: The method comprises the following steps: ​ (1) mixing the waste electrode material and lithium salt and then performing ball milling treatment to obtain a preliminary pre-lithiation material; the ball milling treatment is performed at a speed of 300-500 rpm for 8-10 h; (2) washing, centrifuging and drying the preliminary pre-lithiation material to obtain a pre-lithiation material rich in oxygen defects; the drying is performed at 50-80 ℃ in air for 6-12 h.

2. The method for promoting pre-lithiation of spent electrode material according to claim 1, characterized in that, The ball milling treatment is performed at a ball-to-material ratio of 22-27:

1. 3.The method of facilitating pre-lithiation of spent electrode material according to claim 1, wherein, The lithium salt comprises one or more of lithium hydroxide, lithium carbonate and lithium nitrate.

4. The method for promoting pre-lithiation of spent electrode material according to claim 1 or 3, characterized in that, The molar ratio of lithium in the lithium salt to transition metal in the waste electrode material is (1-1.1):

1.

5. The method for promoting pre-lithiation of spent electrode material according to claim 1, wherein, The washing is performed by repeatedly washing with water at 60-80 ℃ for 3-5 times and then repeatedly washing with anhydrous ethanol for 1-3 times. 6.The method for facilitating pre-lithiation of spent electrode material according to claim 1, wherein, The centrifugation is performed at a speed of 8500-11000 rpm for 5-10 min.

7. The method for promoting pre-lithiation of spent electrode material according to any one of claims 1-6, wherein, The waste electrode material is obtained from waste lithium batteries, and the waste lithium batteries comprise nickel-cobalt-manganese ternary lithium batteries in different proportions.

8. An oxygen-deficient prelithiation material, characterized in that, The pre-lithiation material obtained by the method of any one of claims 1-7 has an increased lithium content of 8-11%.

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