Production method of regenerated negative electrode material based on lithium ion battery

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a production method of a regenerated negative electrode material based on a lithium ion battery, the regenerated negative electrode material comprises a double-layer negative electrode plate or a single-layer negative electrode plate, and the double-layer negative electrode plate or the single-layer negative electrode plate comprises a graphite negative electrode material. The preparation method comprises the following steps: selecting conductive carbon black, styrene-butadiene rubber emulsion and sodium carboxymethyl cellulose in equal mass proportion, adding non-coated graphite or coated graphite, sodium carboxymethyl cellulose, conductive carbon black and styrene-butadiene rubber emulsion into deionized water, uniformly stirring to obtain negative electrode slurry, coating a copper foil with the negative electrode slurry, and drying to obtain the lithium ion battery negative electrode. And the mixed negative plate is obtained after drying, rolling, slitting and tab welding, and has the characteristics of lower internal resistance, higher charging speed and better cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a method for producing a regenerated negative electrode material based on a lithium ion battery. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, low self-discharge rate, and no memory effect. They are widely used in consumer electronics, electric vehicles, and electrochemical energy storage. Currently, consumer electronics such as mobile phones have higher requirements on the volume energy density and fast charging of lithium-ion batteries. Therefore, it is particularly important to design lithium-ion batteries that have both high volume energy density and fast charging performance.

[0003] Methods to increase the volume energy density of lithium-ion batteries include increasing the specific energy of active materials, increasing electrode density, thick electrode design, and reducing separator thickness. Thick electrode design, that is, increasing the loading amount of active materials on the unit surface of the electrode, can reduce the use of separators and current collectors in the battery, increase the proportion of active materials in the battery, and is an effective means to increase the volume energy density. However, the increase in electrode thickness will lead to an increase in the diffusion distance of lithium ions in the electrode, and the uneven distribution of lithium ion concentration in the thickness direction will become more obvious, which will deteriorate the charging performance of lithium-ion batteries.

[0004] For the negative electrode sheet, the increase in polarization will lead to lithium deposition on the surface of the negative electrode sheet, which will lead to serious shortening of the battery cycle life and increased safety risks. Therefore, it is necessary to improve the charging dynamics of the thick negative electrode sheet to avoid lithium deposition.

[0005] Artificial graphite is the most commonly used negative electrode active material for lithium-ion batteries. Its charging dynamics are affected by many factors such as raw materials, particle size, particle structure, and surface coating. Summary of the invention

[0006] In order to solve the problems raised in the above background technology, the present invention provides a method for producing a regenerated negative electrode material based on a lithium-ion battery, which has the characteristics of lower internal resistance, faster charging speed and better cycle performance.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for producing a regenerated negative electrode material based on a lithium-ion battery, comprising a double-layer negative electrode sheet or a single-layer negative electrode sheet, wherein the double-layer negative electrode sheet or the single-layer negative electrode sheet both contain a graphite negative electrode material:

[0008] The production method of graphite negative electrode material includes:

[0009] S1: Select conductive carbon black, styrene-butadiene rubber latex and sodium carboxymethyl cellulose in equal mass proportion.

[0010] S2: Add non-coated graphite or coated graphite, sodium carboxymethyl cellulose, conductive carbon black and styrene-butadiene rubber latex into deionized water, and stir evenly to obtain a negative electrode slurry.

[0011] S3: The negative electrode slurry is coated on a copper foil, and a mixed negative electrode sheet is obtained after drying, rolling, slitting and welding of the electrode tabs.

[0012] As a preferred method for producing a regenerated negative electrode material based on a lithium-ion battery of the present invention, a method for preparing a double-layer negative electrode sheet adopts a coating machine equipped with a double-layer slit extrusion coating die head to simultaneously coat two groups of negative electrode slurries on a copper foil, and obtains a double-layer negative electrode sheet after drying, rolling, slitting and welding the pole lugs;

[0013] The surface layer of the double-layer negative electrode sheet is coated graphite, and the inner layer close to the copper foil is non-coated graphite.

[0014] As a preferred method for producing a regenerated negative electrode material based on a lithium ion battery of the present invention, both the non-coated graphite and the coated graphite are selected from secondary graphite particles with an average particle size of 10-90 microns.

[0015] As a preferred method for producing a regenerated negative electrode material based on a lithium ion battery of the present invention, both the non-coated graphite and the coated graphite are selected from secondary graphite particles with an average particle size of 50 microns.

[0016] As a preferred method for producing a regenerated negative electrode material based on a lithium ion battery of the present invention, the surface layer of the double-layer negative electrode sheet is coated with graphite, and the inner layer close to the copper foil is Z n S n O3 / C composite material.

[0017] As a preferred method for producing a regenerated negative electrode material based on a lithium ion battery of the present invention, Z n S n The preparation method of the O3 / C composite material comprises:

[0018] S1: weigh 10 mmol of Z n CL2, 7mmol S n CL4·5H2O, and 6.5mmol of C6H 12 O6 and mix and stir;

[0019] S2: Mix the mixed and stirred substance with 35 mL of deionized water and stir at room temperature for 30 min to obtain a mixed solution;

[0020] S3: After adding 2 drops of N2H4·H2O to the mixed solution, white floccules are produced, and stirring is continued until the white flocs disappear;

[0021] S4: Transfer the mixed liquid to a high pressure hydrothermal autoclave and heat at 180°C for 24h.

[0022] S5: After the heating is completed, the reaction vessel is opened and the solution is taken out;

[0023] S6: placing the solution taken out from the high pressure hydrothermal autoclave in a centrifuge to collect the solution by centrifugation; then, washing the solution several times with deionized water and anhydrous ethanol;

[0024] S7: After the cleaning is completed, the obtained precipitate is placed in a vacuum drying oven and dried at 90°C for 12 hours to obtain Z n S n O3 / C composite material.

[0025] As a preferred method for producing a regenerated negative electrode material based on a lithium ion battery of the present invention, the method comprises: n S n The inner layer production steps of the double-layer negative electrode sheet of O3 / C composite material include:

[0026] S1: Z with a mass ratio of 8:1:1 n S n The O3 / C composite material, acetylene black, sodium alginate and deionized water are uniformly mixed to obtain a slurry;

[0027] S2: evenly apply the obtained slurry on the copper foil;

[0028] S3: Place the copper foil evenly coated with the slurry in a vacuum drying oven and operate at 100°C for 12 hours;

[0029] S4: taking out the copper foil, rolling, slitting and welding the tabs to obtain a mixed negative electrode sheet.

[0030] Compared with the prior art, the beneficial effects of the present invention are: since the interlayer spacing of graphite materials is relatively small, it is not conducive to the diffusion of lithium ions, and amorphous carbon has a larger interlayer spacing, which is conducive to the diffusion of lithium ions, so surface coating of amorphous carbon is an effective means to improve the charging kinetics of graphite; the composite use of high-kinetic active substances in the negative electrode sheet can obtain a negative electrode material with good charging kinetics.

[0031] In addition to negative electrode active materials, the charging dynamics can also be improved from the structural design of the negative electrode sheet; the double-layer negative electrode has lower polarization when charged at a high rate than the single-layer negative electrode; the use of double-layer negative electrodes, high-porosity diaphragms, fast-charging electrolytes and other means enables the battery to be cycled 600 times super-fast without lithium deposition; negative electrode sheets with a gradient distribution of graphite particle size and electrode porosity have better fast-charging performance than conventional negative electrode sheets.

[0032] Since coated graphite will reduce the electrode density and the initial charge and discharge efficiency, thus affecting the volume energy density of lithium-ion batteries, the loss of energy density can be alleviated by using a composite of non-coated graphite with high compaction density and high initial charge and discharge efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 The SEM images of non-coated graphite and coated graphite;

[0035] Figure 2 This is the X-ray photoelectron spectrometer spectrum. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] A method for producing a regenerated negative electrode material based on a lithium-ion battery, comprising a double-layer negative electrode sheet or a single-layer negative electrode sheet, wherein the double-layer negative electrode sheet or the single-layer negative electrode sheet contains a graphite negative electrode material:

[0038] The production method of graphite negative electrode material includes:

[0039] S1: Select conductive carbon black (conductive agent), styrene-butadiene rubber latex (binder) and sodium carboxymethyl cellulose (dispersant) in equal proportion by mass.

[0040] S2: Add non-coated graphite or coated graphite, sodium carboxymethyl cellulose, conductive carbon black and styrene-butadiene rubber latex into deionized water, and stir evenly to obtain a negative electrode slurry.

[0041] S3: The negative electrode slurry is coated on a copper foil, and a mixed negative electrode sheet is obtained after drying, rolling, slitting and welding of the electrode tabs.

[0042] In an optional embodiment, the preparation method of the double-layer negative electrode sheet is to use a coating machine equipped with a double-layer slot extrusion coating die to simultaneously coat two groups of negative electrode slurries on copper foil, and obtain the double-layer negative electrode sheet after drying, rolling, slitting and welding the pole ears;

[0043] The surface layer of the double-layer negative electrode sheet is coated graphite, and the inner layer close to the copper foil is non-coated graphite.

[0044] The preparation method of the double-layer negative electrode sheet is to prepare negative electrode slurries of non-coated graphite and coated graphite respectively, and the preparation methods are the same, and then a coating machine equipped with a double-layer slit extrusion coating die is used to simultaneously coat the two groups of negative electrode slurries on the copper foil, and the double-layer negative electrode sheet is obtained after drying, rolling, slitting and welding the pole ears. The surface layer of the double-layer negative electrode sheet is coated graphite, and the non-coated graphite is close to the copper foil (bottom layer). The surface layer and the bottom layer of the double-layer negative electrode sheet have the same surface density, that is, the mass of the non-coated graphite and the coated graphite in the double-layer electrode sheet is equal. In order to ensure that the surface density of the surface layer and the bottom layer is the same, the bottom layer and the surface layer slurry are coated separately first, and it is confirmed that the coating surface density meets the requirements, and then the double layers are arranged to be coated at the same time. The design surface density of the double-layer negative electrode sheet and the mixed negative electrode sheet is the same.

[0045] In an optional embodiment, both the non-coated graphite and the coated graphite are secondary graphite particles with an average particle size of 10-90 microns.

[0046] In this embodiment, Figure 1 As shown in Table 1, Figure 1 (a) is uncoated graphite and (b) is coated graphite. Both uncoated graphite and coated graphite are composed of secondary graphite particles with smaller particle size. The uncoated graphite is relatively more obvious. This structure is beneficial to reduce the O / I value of graphite and improve the volume expansion during the electrode cycle. The uncoated graphite particles have clear edges and corners, while the coated graphite particles have a smoother surface, indicating that coating amorphous carbon can change the surface morphology of graphite particles and reduce defects on the particle surface.

[0047] Table 1

[0048]

[0049] In an optional embodiment, both the non-coated graphite and the coated graphite are secondary graphite particles with an average particle size of 50 microns.

[0050] In this embodiment, as shown in Table 1, in order to better understand the material properties of the two groups of graphite, the material particle size, specific surface area, gram capacity and initial charge and discharge efficiency were tested. From the particle size results, it can be seen that the median particle size D50 of the two groups of graphite is relatively close, the coated graphite is relatively large, and the particle size distribution of the coated graphite is relatively narrower. The specific surface areas of the coated graphite and the non-coated graphite are 0.98 m 2 ·g -1 and 1.60m 2 ·g -1 , the specific surface area of ​​coated graphite is small, indicating that graphite-coated amorphous carbon can fill part of the pores on the particle surface;

[0051] This result is consistent with Figure 1It was observed that the surface of the coated graphite was smoother; the gram capacity and first charge and discharge efficiency of the two groups of graphite were tested using button batteries; the gram capacity and first charge and discharge efficiency of the coated graphite were lower.

[0052] In an optional embodiment, the surface layer of the double-layer negative electrode sheet is coated with graphite, and the inner layer near the copper foil is Z n S n O3 / C composite material.

[0053] In an alternative embodiment, Z n S n The preparation method of the O3 / C composite material comprises:

[0054] S1: weigh 10 mmol of Z n CL2, 7mmol S n CL4·5H2O, and 6.5mmol of C6H 12 O6 and mix and stir;

[0055] S2: Mix the mixed and stirred substance with 35 mL of deionized water and stir at room temperature for 30 min to obtain a mixed solution;

[0056] S3: After adding 2 drops of N2H4·H2O to the mixed solution, white floccules are produced, and stirring is continued until the white flocs disappear;

[0057] S4: Transfer the mixed liquid to a high pressure hydrothermal autoclave and heat at 180°C for 24h.

[0058] S5: After the heating is completed, the reaction vessel is opened and the solution is taken out;

[0059] S6: placing the solution taken out from the high pressure hydrothermal autoclave in a centrifuge to collect the solution by centrifugation; then, washing the solution several times with deionized water and anhydrous ethanol;

[0060] S7: After the cleaning is completed, the obtained precipitate is placed in a vacuum drying oven and dried at 90°C for 12 hours to obtain Z n S n O3 / C composite material.

[0061] In this embodiment, the capacity of the commonly used commercial graphite negative electrode is relatively low, only 372 mAh. 2 ·g -1 , which limits the application of lithium-ion batteries to a certain extent. Based on the existing research theory, the bimetallic oxide zinc stannate (Z n S n O3) materials have good advantages over single metal oxides (such as S nO2) has a higher theoretical specific capacity (1317mAh) 2 ·g -1 ), higher conductivity (2.5×102S·cm –1 ) and lower working voltage. At the same time, zinc stannate, as a bimetallic oxide, plays a role in lithium-ion batteries. n O can relieve S n The volume change caused by O2 during lithium storage can prevent the deformation of zinc stannate. However, from a practical point of view, the use of pure zinc stannate as an electrode material has problems such as pulverization, agglomeration and poor contact between active materials. Therefore, Z n S n The application of O3 / C composite materials can better solve the problem of relatively poor conductivity and volume deformation of zinc stannate;

[0062] like Figure 2 As shown in the figure, (a) is the full spectrum, (b) Zn2p, (c) Sn3d, and (d) the high-resolution XPS spectrum near the binding energy of C1s. The prepared materials were scanned with a field emission scanning electron microscope and a transmission electron microscope, and it was finally found that pure Z n S n O3 material is a structure composed of nanoparticles, the size of which is in the range of 10-20nm. n S n The specific surface area of ​​O3 / C composite material is 154.4m 2 ·g –1 The surface area of ​​pure ZnSnO3 is larger than that of pure ZnSnO3. The composite material is composed of smaller nanostructures. Most of the nanostructured materials are spherical, with better dispersion and more uniform appearance. n S n The distance between O3 and the carbon coating layer is 0.29nm. It can be seen that since the composite material has a larger specific surface area, in lithium-ion batteries, it can increase the contact area with the electrolyte, thereby optimizing the battery storage performance.

[0063] In an optional embodiment, Z n S n The inner layer production steps of the double-layer negative electrode sheet of O3 / C composite material include:

[0064] S1: Z with a mass ratio of 8:1:1 n S n The O3 / C composite material, acetylene black, sodium alginate and deionized water are uniformly mixed to obtain a slurry;

[0065] S2: evenly apply the obtained slurry on the copper foil;

[0066] S3: Place the copper foil evenly coated with the slurry in a vacuum drying oven and operate at 100°C for 12 hours;

[0067] S4: taking out the copper foil, rolling, slitting and welding the tabs to obtain a mixed negative electrode sheet.

[0068] In this embodiment, since the composite material has a larger specific surface area, the contact area with the electrolyte can be increased in the lithium-ion battery. n S n The O3 / C composite material is used as the inner layer of the double-layer negative electrode sheet and can solve the problem of volume deformation. On this basis, the coated graphite on the surface of the double-layer negative electrode sheet can avoid precipitation and falling off due to volume change.

[0069] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing a regenerated negative electrode material based on a lithium-ion battery, characterized in that: Including a double-layer negative electrode sheet or a single-layer negative electrode sheet, both of which contain graphite negative electrode materials: The production method of graphite negative electrode material includes: S1: Select conductive carbon black, styrene-butadiene rubber latex and sodium carboxymethyl cellulose in equal mass proportion. S2: Add non-coated graphite or coated graphite, sodium carboxymethyl cellulose, conductive carbon black and styrene-butadiene rubber latex into deionized water, and stir evenly to obtain a negative electrode slurry. S3: The negative electrode slurry is coated on a copper foil, and a mixed negative electrode sheet is obtained after drying, rolling, slitting and welding of the electrode tabs.

2. The method for producing a regenerated negative electrode material based on a lithium ion battery according to claim 1, characterized in that: The preparation method of the double-layer negative electrode sheet is to use a coating machine equipped with a double-layer slot extrusion coating die to simultaneously coat two groups of negative electrode slurries on copper foil, and obtain the double-layer negative electrode sheet after drying, rolling, slitting and welding the pole ears; The surface layer of the double-layer negative electrode sheet is coated graphite, and the inner layer close to the copper foil is non-coated graphite.

3. The method for producing a regenerated negative electrode material based on a lithium ion battery according to claim 1 or 2, characterized in that: Both the non-coated graphite and the coated graphite are secondary graphite particles with an average particle size of 10-90 microns.

4. The method for producing a regenerated negative electrode material based on a lithium ion battery according to claim 3, characterized in that: Both the non-coated graphite and the coated graphite are secondary graphite particles with an average particle size of 50 microns.

5. The method for producing a regenerated negative electrode material based on a lithium ion battery according to claim 1, 2 or 4, characterized in that: The surface layer of the double-layer negative electrode sheet is coated with graphite, and the inner layer near the copper foil contains Z n S n O3 / C composite material.

6. The method for producing a regenerated negative electrode material based on a lithium ion battery according to claim 5, characterized in that: Z n S n The preparation method of the O3 / C composite material comprises: S1: weigh 10 mmol of Z n CL2, 7mmol S n CL4·5H2O, and 6.5mmol of C6H 12 O6 and mix and stir; S2: Mix the mixed and stirred substance with 35 mL of deionized water and stir at room temperature for 30 min to obtain a mixed solution; S3: After adding 2 drops of N2H4·H2O to the mixed solution, white floccules are produced, and stirring is continued until the white flocs disappear; S4: Transfer the uniformly mixed liquid to a high pressure hydrothermal autoclave and heat at 180°C for 24h. S5: After the heating is completed, the mixture is cooled to room temperature, the reactor is opened, and the solution is taken out; S6: placing the solution taken out from the high pressure hydrothermal autoclave in a centrifuge to collect the solution by centrifugation; then, washing the solution several times with deionized water and anhydrous ethanol; S7: After the cleaning is completed, the obtained precipitate is placed in a vacuum drying oven and dried at 90°C for 12 hours to obtain Z n S n O3 / C composite material.

7. The method for producing a regenerated negative electrode material based on a lithium ion battery according to claim 6, characterized in that: Contains Z n S n The inner layer production steps of the double-layer negative electrode sheet of O3 / C composite material include: S1: Z with a mass ratio of 8:1:1 n S n The O3 / C composite material, acetylene black, sodium alginate and deionized water are uniformly mixed to obtain a slurry; S2: evenly apply the obtained slurry on the copper foil; S3: Place the copper foil evenly coated with the slurry in a vacuum drying oven and operate at 100°C for 12 hours; S4: taking out the copper foil, rolling, slitting and welding the tabs to obtain a mixed negative electrode sheet.

Images