Pre-lithiation regeneration method of waste graphite as well as product and application of pre-lithiation regeneration method

Abstract

The invention relates to a pre-lithiation regeneration method of waste graphite as well as a product and application thereof, and relates to the technical field of lithium batteries. The invention provides a pre-lithiation regeneration method of waste graphite. The pre-lithiation regeneration method comprises the following steps: (1) respectively preparing waste graphite into a cathode electrode plate and an anode electrode plate; and (2) placing the cathode electrode plate and the anode electrode plate in an electrolyte of a CDI device, applying voltage for pre-lithiation, and taking out the pre-lithiated cathode electrode plate to obtain the pre-lithiated graphite material. Efficient pre-lithiation of the waste graphite is achieved through the capacitive deionization technology, the lithium embedding amount can be accurately controlled, and the electrochemical performance of the waste graphite is improved. Compared with the traditional method, the method disclosed by the invention is low in cost, low in energy consumption, small in pollution and good in environmental benefit.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology; specifically, it relates to a pre-lithiation regeneration method for waste graphite, its products, and applications. Background Technology

[0002] With the widespread application of lithium-ion batteries, the recycling and reuse of waste graphite has become an important research direction. Traditional graphite regeneration methods suffer from high energy consumption and serious environmental pollution. Capacitor deionization (CDI), as a highly efficient and environmentally friendly ion separation technology, has been widely used in water treatment and other fields in recent years.

[0003] Existing pre-lithiation methods mainly rely on chemical reactions or high-temperature treatments, which are not only costly but also difficult to precisely control the amount of lithium intercalation. Therefore, developing an efficient, controllable, and environmentally friendly pre-lithiation regeneration method for waste graphite is of great significance. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a pre-lithiation regeneration method for waste graphite, along with its products and applications. This invention achieves efficient pre-lithiation of waste graphite through capacitive deionization technology, allowing for precise control of lithium intercalation and improving its electrochemical performance. Compared to traditional methods, the method of this invention is low-cost, low-energy-consumption, and low-pollution, offering significant environmental benefits.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The first objective of this invention is to provide a pre-lithiation regeneration method for waste graphite, comprising the following steps: (1) The waste graphite is made into cathode electrode plates and anode electrode plates respectively; (2) The cathode electrode and the anode electrode are placed in the electrolyte of the CDI device, and a voltage is applied for pre-lithiation. The pre-lithiated cathode electrode is then removed to obtain the pre-lithiated graphite material.

[0006] The beneficial effects of this invention are: This invention achieves efficient pre-lithiation of waste graphite through capacitive deionization technology, allowing for precise control of lithium intercalation and improving its electrochemical performance. The pre-lithiated anode electrode can be recycled. Compared to traditional methods, this invention is low-cost, low-energy, and low-polluting, offering significant environmental benefits.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Further, step (1) is as follows: pre-treat waste graphite to obtain waste graphite powder; mix the waste graphite powder with conductive agent and binder, add solvent to obtain slurry, coat the slurry on the current collector, and then dry to obtain cathode electrode sheet and anode electrode sheet.

[0009] The beneficial effects of adopting the above-mentioned further solutions are: improved electrode conductivity and electrolyte permeability.

[0010] Furthermore, the pretreatment specifically involves grinding waste graphite and passing it through a 100-mesh sieve to obtain waste graphite powder.

[0011] Furthermore, the mass ratio of the waste graphite powder, the conductive agent, and the binder is 7~9:0.5~2:0.5~2.

[0012] Furthermore, the current collector is a copper foil with a porosity ≥80%; the solvent is NMP; the conductive agent is carbon black; and the binder is PVDF.

[0013] Furthermore, the ratio of NMP to PVDF is 20:1; the slurry is coated onto the current collector using a coating machine at a flow rate of 6 mL / min.

[0014] Furthermore, the concentration of the electrolyte in step (2) is 0.5M~2M; the electrolyte is at least one of LiCl solution, LiSO4 solution, and LiClO4 solution.

[0015] The beneficial effects of adopting the above-mentioned further scheme are: the migration driving force includes the synergistic effect of electric field force and concentration gradient, and the lithium intercalation amount can be precisely controlled by adjusting the electrolyte concentration to meet the needs of different application scenarios.

[0016] Furthermore, in step (2), a DC voltage of 3V~5V is applied, and the pre-lithiation treatment time is 30min~120min.

[0017] The beneficial effect of adopting the above further scheme is that applying a DC voltage makes Li + Migrating towards the cathode and embedding between graphite layers, while Cl... - Migration towards the anode; by adjusting the voltage and processing time, the migration speed and embedding amount of lithium ions can be precisely controlled to meet the needs of different application scenarios; too low a voltage will prevent lithium ions from embedding, and too high a voltage will also reduce the embedding amount of lithium ions, which is not conducive to pre-lithiation.

[0018] Furthermore, the CDI device includes a symmetrical electrode tank, an anion exchange membrane, a cation exchange membrane, an electrolyte, a power supply module; a cathode electrode plate and an anode electrode plate; The top of the symmetrical electrode tank has four insertion holes, through which the cathode electrode plate, the anion exchange membrane, the cation exchange membrane, and the anode electrode plate extend into the interior of the symmetrical electrode tank. The anion exchange membrane and the cation exchange membrane are respectively disposed on both sides of the symmetrical electrode tank; the cathode electrode plate is disposed on the side of the anion exchange membrane near the inner wall of the symmetrical electrode tank; the anode electrode plate is disposed on the side of the cation exchange membrane near the inner wall of the symmetrical electrode tank. The electrolyte is contained in the symmetrical electrode tank; the anode electrode and the cathode electrode are respectively connected to the power module via wires; the power module is located at the top of the symmetrical electrode tank.

[0019] The beneficial effect of adopting the above-mentioned further scheme is that by immersing the cathode and anode electrode plates in LiCl solution and applying DC voltage using a constant voltage DC power supply module, the LiCl electrode becomes more soluble in LiCl. + Migrating towards the cathode and embedding between graphite layers, while Cl... - Migrate towards the anode.

[0020] Furthermore, a lithium-ion concentration detection sensor is also installed at the top of the symmetrical electrode tank, and the lithium-ion concentration detection sensor is connected to the power module via a control line.

[0021] The beneficial effect of adopting the above-mentioned further scheme is that it allows for real-time monitoring of the lithium ion concentration in the electrolyte, so as to accurately control the pre-lithiation process.

[0022] A second objective of this invention is to provide a pre-lithiated graphite material.

[0023] Furthermore, the Raman spectral ID / IG value of the pre-lithiated graphite material is 0.85~1.20.

[0024] The beneficial effects of adopting the above-mentioned further scheme are: the pre-lithiated graphite material prepared by the present invention exhibits local disordered characteristics in its crystal structure (the interlayer spacing of the 002 crystal plane is expanded to 0.340-0.350 nm, and the ID / IG value is ≥0.85). The local disordered characteristics in the crystal structure of the pre-lithiated graphite are beneficial to improving its electrochemical performance.

[0025] A third objective of this invention is to provide an application of a pre-lithiated graphite material, which is used in the negative electrode of a lithium-ion battery.

[0026] The beneficial effects of this invention are: the pre-lithiated graphite material regenerated by this invention exhibits excellent electrochemical performance when used in the negative electrode of lithium-ion batteries. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the CDI device of the present invention.

[0028] The attached diagram lists the components represented by each number as follows: 1. Power module; 2. Control line; 3. Lithium-ion concentration monitoring sensor; 4. Wire; 5. Negative electrode plate; 6. Symmetrical electrode tank; 7. Anion exchange membrane; 8. Cation exchange membrane; 9. Positive electrode plate; 10. Electrolyte. Detailed Implementation

[0029] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0030] Example 1: A CDI device, such as Figure 1 As shown, the device includes a symmetrical electrode tank 6, an anion exchange membrane 7, a cation exchange membrane 8, an electrolyte 10, and a power module 1; as well as a cathode electrode 5 and an anode electrode 9. The symmetrical electrode tank 6 is box-shaped with four insertion holes at the top. The cathode electrode 5, anion exchange membrane 7, cation exchange membrane 8, and anode electrode 9 extend into the interior of the symmetrical electrode tank 6 through these insertion holes. The anion exchange membrane 7 and cation exchange membrane 8 are respectively located on both sides of the symmetrical electrode tank 6. The cathode electrode 5 is located on the side of the anion exchange membrane 7 near the inner wall of the symmetrical electrode tank 6. The anode electrode 9 is located on the side of the cation exchange membrane 8 near the inner wall of the symmetrical electrode tank 6. The electrolyte 10 is contained within the symmetrical electrode tank 6. The anode electrode 9 and cathode electrode 5 are respectively connected to the power module 1 via wires 4. The power module 1 is located at the top of the symmetrical electrode tank 6. A lithium-ion concentration detection sensor 3 is also installed at the top of the symmetrical electrode tank 6. The lithium-ion concentration detection sensor 3 is connected to the power module 1 through the control line 2.

[0031] Example 2: (1) Grind waste graphite and pass it through a 100-mesh sieve to obtain waste graphite powder; mix the waste graphite powder with carbon black and PVDF in a mass ratio of 8:1:1, add NMP to make a slurry, wherein the ratio of NMP to PVDF is 20mL:1g. Coat the slurry evenly on copper foil, dry it and cut it into circular electrode sheets with a diameter of 14mm; (2) The prepared circular electrode sheets were placed in a 1M LiCl solution as cathode and anode electrodes to form the CDI device of Example 1. A DC voltage of 3V was applied for 60 minutes to obtain pre-lithiated graphite material.

[0032] Example 3: (1) Grind waste graphite and pass it through a 100-mesh sieve to obtain waste graphite powder; mix the waste graphite powder with carbon black and PVDF in a mass ratio of 8:1:1, add NMP to make a slurry, wherein the ratio of NMP to PVDF is 20mL:1g. Coat the slurry evenly on copper foil, dry it and cut it into circular electrode sheets with a diameter of 14mm; (2) The prepared circular electrode sheets were placed in a 2M LiCl solution as cathode and anode electrodes to form the CDI device of Example 1. A DC voltage of 4V was applied for 90 minutes to obtain pre-lithiated graphite material.

[0033] Example 4: (1) Grind waste graphite and pass it through a 100-mesh sieve to obtain waste graphite powder; mix the waste graphite powder with carbon black and PVDF in a mass ratio of 8:1:1, add NMP to make a slurry, wherein the ratio of NMP to PVDF is 20mL:1g. Coat the slurry evenly on copper foil, dry it and cut it into circular electrode sheets with a diameter of 14mm; (2) The prepared circular electrode sheets were placed in a 2M LiCl solution as cathode and anode electrodes to form the CDI device of Example 1. A DC voltage of 5V was applied for 150 minutes to obtain pre-lithiated graphite material.

[0034] Comparative Example 1: (1) Grind waste graphite and pass it through a 100-mesh sieve to obtain waste graphite powder; mix the waste graphite powder with carbon black and PVDF in a mass ratio of 8:1:1, add NMP to make a slurry, wherein the ratio of NMP to PVDF is 20mL:1g. Coat the slurry evenly on copper foil, dry it and cut it into circular electrode sheets with a diameter of 14mm; (2) The prepared circular electrode sheets were placed in a 0.5M LiCl solution as cathode and anode respectively to form the CDI device of Example 1. A DC voltage of 2V was applied for 120min to obtain pre-lithiated graphite material.

[0035] Performance testing: (1) Material structure characterization: The pre-lithiated graphite prepared in Example 2 was characterized using a D8 ADVANCE X-ray diffractometer (Bruck) and an inVia Qontor Raman spectrometer (Renishaw). XRD patterns and Raman spectra were obtained, and the test results showed: XRD pattern: The diffraction peak of the 002 crystal plane shifts to a smaller angle, and the interlayer spacing increases to 0.340-0.350 nm (0.335 nm for untreated graphite). Raman spectrum: D peak (1350 cm⁻¹) -1 ) and G peak (1580 cm)-1 The intensity ratio ID / IG ≥ 0.85 (≤ 0.25 for untreated graphite) indicates that pre-lithiation leads to local disorder in the crystal structure. (2) Lithium intercalation determination: The lithium content was tested by inductively coupled plasma optical emission spectrometry (ICP-OES, PerkinElmer Optima 8300), and the lithium intercalation was calculated. The results are shown in Table 1.

[0036] (3) Half-cell test: The pre-lithiated graphite materials prepared in Examples 2-4 and Comparative Example 1 were used as positive electrodes for half-cell testing. The negative electrode was a lithium sheet, and the electrolyte was 1M LiPF6 (the solvent was ethylene carbonate EC and diethyl carbonate DMC, with a volume ratio of EC to DMC of 1:1); the separator was Celgard 2325, and the voltage window was 0.01-2.0V (vs. Li + / Li); temperature 25±1℃; after 500 cycles at 0.1C, the electrode material exhibits the following properties, as shown in Table 1.

[0037] Table 1 From Table 1, we can obtain: (1) In the half-cell test, the pre-lithiated graphite as the negative electrode material has a capacity retention rate of ≥118% after 500 cycles at 0.1C rate; initial coulombic efficiency of 68%; and reversible capacity of ≥382 mAh / g at 0.1C rate.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for pre-lithiation regeneration of waste graphite, characterized in that, Includes the following steps: (1) The waste graphite is made into cathode electrode plates and anode electrode plates respectively; (2) The cathode electrode and the anode electrode are placed in the electrolyte of the CDI device, and a voltage is applied for pre-lithiation. The pre-lithiated cathode electrode is then removed to obtain the pre-lithiated graphite material.

2. The pre-lithiation regeneration method for waste graphite according to claim 1, characterized in that, Step (1) is as follows: waste graphite is pretreated to obtain waste graphite powder; the waste graphite powder is mixed with conductive agent and binder, and then a solvent is added to obtain slurry; the slurry is coated on current collector and then dried to obtain cathode electrode sheet and anode electrode sheet.

3. The pre-lithiation regeneration method for waste graphite according to claim 2, characterized in that, The mass ratio of the waste graphite powder, the conductive agent, and the binder is 7~9:0.5~2:0.5~2.

4. The pre-lithiation regeneration method for waste graphite according to claim 1, characterized in that, The concentration of the electrolyte in step (2) is 0.5M~2M; the electrolyte is at least one of LiCl solution, LiSO4 solution, and LiClO4 solution.

5. The pre-lithiation regeneration method for waste graphite according to claim 1, characterized in that, In step (2), a DC voltage of 3V to 5V is applied, and the pre-lithiation treatment time is 30min to 120min.

6. The pre-lithiation regeneration method for waste graphite according to claim 1, characterized in that, The CDI device includes a symmetrical electrode tank (6), an anion exchange membrane (7), a cation exchange membrane (8), an electrolyte (10), a power supply module (1), the cathode electrode plate (5), and the anode electrode plate (9). The top of the symmetrical electrode tank (6) has four insertion holes, through which the cathode electrode plate (5), the anion exchange membrane (7), the cation exchange membrane (8), and the anode electrode plate (9) extend into the interior of the symmetrical electrode tank (6); The anion exchange membrane (7) and the cation exchange membrane (8) are respectively disposed on both sides of the symmetrical electrode tank (6); the cathode electrode plate (5) is disposed on the side of the anion exchange membrane (7) near the inner wall of the symmetrical electrode tank (6); the anode electrode plate (9) is disposed on the side of the cation exchange membrane (8) near the inner wall of the symmetrical electrode tank (6). The electrolyte (10) is contained in the symmetrical electrode tank (6); the anode electrode (9) and the cathode electrode (5) are respectively connected to the power module (1) via wires (4); the power module (1) is located at the top of the symmetrical electrode tank (6).

7. The pre-lithiation regeneration method for waste graphite according to claim 6, characterized in that, A lithium ion concentration detection sensor (3) is also installed at the top of the symmetrical electrode tank (6), and the lithium ion concentration detection sensor (3) is connected to the power module (1) through a control line (2).

8. A pre-lithiated graphite material, characterized in that, It is prepared by the regeneration method according to any one of claims 1 to 7.

9. A pre-lithiated graphite material according to claim 8, characterized in that, The Raman spectral ID / IG value of the pre-lithiated graphite material is 0.85~1.

20.

10. An application of a pre-lithiated graphite material, characterized in that, The pre-lithiated graphite material according to any one of claims 8 to 9 is used in the negative electrode of a lithium-ion battery.

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