Negative electrode material compositely derived from natural graphite and artificial graphite, preparation and lithium ion battery

Abstract

The invention relates to a natural graphite and artificial graphite composite derived negative electrode material, preparation and a lithium ion battery, and belongs to the technical field of lithium ion batteries. Natural graphite and artificial graphite are used as main active substances, a proper amount of polyvinylpyrrolidone is added to serve as a polymer binder and a dispersing agent, and the electrode microstructure is optimized by accurately regulating and controlling the dosage of each substance, so that the cycling stability and the rate capability of the graphite negative electrode are improved. The composite strategy can effectively combine the high-capacity characteristic of natural graphite and the structural stability of artificial graphite, and the cycle life of the material is remarkably prolonged while the electrochemical dynamic behavior of the material is improved.

Description

Technical Field

[0001] This invention relates to a negative electrode material derived from a composite of natural graphite and artificial graphite, its preparation, and a lithium-ion battery, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Against the backdrop of global environmental degradation and the depletion of fossil fuels, human society urgently needs to transform from a high-pollution, high-energy-consumption production and lifestyle to a green and sustainable development model. Currently, energy technology innovation has become a global consensus. In the process of achieving effective utilization of new energy sources, energy storage and conversion are crucial. Lithium-ion batteries, due to their advantages such as high energy density, long cycle life, low self-discharge rate, light weight, and environmental friendliness, have become the most commercially successful rechargeable battery technology.

[0003] As a core component of lithium-ion batteries, the performance of anode materials directly affects the overall performance of the battery. Currently, graphite-based materials dominate the anode market, mainly divided into two categories: natural graphite and artificial graphite. Unlike mineral-extracted natural graphite, artificial graphite is typically produced using petroleum coke, needle coke, etc., as precursors through pre-carbonization and high-temperature graphitization processes. It possesses a highly ordered layered structure and excellent cycle stability, thus being widely used in electric vehicle power batteries and energy storage systems. However, the preparation process of artificial graphite is energy-intensive and generates significant carbon emissions; simultaneously, its production cost is relatively high, which to some extent limits its further large-scale application. Therefore, the development of natural / artificial graphite composite anode materials that combine low energy consumption, low cost, and high stability has become a common research hotspot in both industry and academia.

[0004] While composite modification is a common strategy for optimizing material properties, simply combining natural and synthetic graphite through mechanical mixing can easily lead to uneven particle aggregation, affecting the material's conductive network and lithium-ion transport kinetics, ultimately impairing its electrochemical performance. Therefore, developing a composite process that can achieve uniform bonding and controllable structure is particularly important. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a negative electrode material derived from a composite of natural and artificial graphite, its preparation, and a lithium-ion battery. This invention uses natural and artificial graphite as the main active materials, and adds an appropriate amount of polyvinylpyrrolidone (PVP) as a polymer binder and dispersant. By precisely controlling the amount of each substance, the electrode microstructure is optimized, thereby improving the cycle stability and rate performance of the graphite negative electrode. This composite strategy effectively combines the high capacity characteristics of natural graphite with the structural stability of artificial graphite, significantly extending its cycle life while improving the electrochemical kinetics of the material. This provides strong technical support for the development of low-cost, long-life, and environmentally friendly graphite-based negative electrode materials.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite, the method comprising the following steps:

[0008] Natural graphite and artificial graphite are centrifuged together to obtain mixed graphite; the mass ratio of natural graphite to artificial graphite is 3:7 to 7:3. (2) Disperse the mixed graphite in deionized water to obtain a mixed graphite dispersion; (3) Add polyvinylpyrrolidone (PVP) to the mixed graphite dispersion and stir magnetically to obtain a mixture; the mass ratio of PVP to mixed graphite is 0.03:1~0.05:1; (4) Add the mixture to a spray dryer for spray drying. The inlet temperature is 110~130℃ and the feed rate is 80 mL / min~150 mL / min. Collect the sprayed powder to obtain a negative electrode material derived from natural graphite and artificial graphite composite.

[0009] Preferably, in step (1), the mass ratio of natural graphite to artificial graphite is 4:6 to 6:4.

[0010] Preferably, in step (1), the particle size of the natural graphite and the artificial graphite is 100~300 mesh.

[0011] Preferably, in step (1), the rotation speed of the centrifugal mixer is 2500~3000 rpm.

[0012] Preferably, in step (1), the centrifugal mixing time is 5 to 10 minutes.

[0013] Preferably, in step (2), the mass concentration of the mixed graphite dispersion is 8~10 g / L.

[0014] Preferably, in step (3), the rotation speed of the magnetic stirrer is 300~350 rpm.

[0015] Preferably, in step (3), the stirring time is 1 to 1.5 h.

[0016] A negative electrode material derived from a composite of natural graphite and artificial graphite was prepared by the above method.

[0017] A lithium-ion battery, wherein the negative electrode material of the battery is a negative electrode material derived from a composite of natural graphite and artificial graphite as described in this invention.

[0018] Beneficial effects The method described in this invention prepares a lithium-ion battery anode material with uniform structure and excellent performance by combining natural graphite and artificial graphite using a spray drying process. The process incorporates optimized design and precise control in several key steps, significantly improving the overall performance of the material. Specifically, centrifugal mixing achieves uniform dispersion of the two types of graphite, avoiding stratification due to differences in physical properties and laying the structural foundation for material uniformity. Subsequently, PVP is introduced and thoroughly stirred before spray drying. Utilizing the bonding, dispersion, and film-forming properties of PVP, particle bonding, surface defect repair, and droplet homogenization are simultaneously achieved during spray drying, thereby improving electrochemical performance. By precisely controlling the spray drying inlet air temperature to 110–130℃, effective PVP bonding and particle formation are ensured while preventing binder decomposition or graphite structure damage due to excessive temperature, thus guaranteeing the structural integrity and conductive stability of the material. Through the synergistic effect of the above processes, this invention achieves an effective combination of the high capacity of natural graphite and the high stability of artificial graphite. The resulting anode material has excellent cycle performance, rate performance and structural reliability. Moreover, the process is simple and energy consumption is low, making it suitable for large-scale production. This provides a practical and feasible technical solution for the development of high-performance, low-cost graphite-based anodes. Attached Figure Description

[0019] Figure 1 This is an SEM image of the final product in Example 1.

[0020] Figure 2 This is an SEM image of the final product in Example 2.

[0021] Figure 3 This is an SEM image of the final product in Example 3.

[0022] Figure 4 This is a SEM image of the final product in Comparative Example 4.

[0023] Figure 5 The XRD diffraction patterns and magnified patterns of the final products in Examples 1, 2, 3 and Comparative Example 1 are shown.

[0024] Figure 6The images show the Raman spectra of the final products in Examples 1, 2, 3 and Comparative Example 1.

[0025] Figure 7 The first-week charge-discharge curves of the batteries assembled from the final products of Examples 1, 2, 3 and Comparative Example 1 at a current density of 0.1C are shown.

[0026] Figure 8 The graph shows the cycling performance of batteries assembled from the final products of Examples 1, 2, 3 and Comparative Example 1 at a current density of 1C.

[0027] Figure 9 Nyquist plot of batteries assembled from the final products of Examples 1, 2, 3 and Comparative Example 1 after 1 cycle.

[0028] Figure 10 Nyquist plot of batteries assembled from the final products of Examples 1, 2, 3 and Comparative Example 1 after 10 cycles.

[0029] Figure 11 Nyquist plot of batteries assembled from the final products of Examples 1, 2, 3 and Comparative Example 1 after 100 cycles.

[0030] Figure 12 The image shows the EDS diagram of the electrode sheet of the battery assembled from the final product in Example 1 after cycling.

[0031] Figure 13 The image shows the EDS diagram of the electrode sheet of the battery assembled from the final product in Example 2 after cycling.

[0032] Figure 14 The image shows the EDS diagram of the electrode sheet of the battery assembled from the final product in Example 3 after cycling.

[0033] Figure 15 EDS plot of the electrode sheet of the battery assembled from the final product in Comparative Example 1 after cycling. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments.

[0035] In the following examples and comparative examples, battery assembly and testing were performed as follows: The final product in the examples or comparative examples was a slurry obtained by mixing high-performance conductive carbon black Super P and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. This slurry was coated onto copper foil to form a negative electrode sheet. A lithium metal sheet was used as the positive electrode, a Ceglard 2500 polypropylene membrane as the separator, and LB315 as the electrolyte (wherein the solvent is ethylene carbonate and ethyl methyl carbonate at a mass ratio of 3:7, and the solute is 1M LiPF6). The batteries were assembled into button cells in an argon-filled glove box. After the batteries were left to stand for 12 hours, they were cycled at 0.1C-10C rates. The test voltage range was 0.005V-2.5V, and the 1C current density was defined as 300mA / g.

[0036] Example 1 (1) Weigh 0.3g of natural graphite with a particle size of 100 mesh and 0.7g of artificial graphite with a particle size of 100 mesh respectively, and centrifuge them in a centrifuge mixer at a speed of 3000 rpm for 5 minutes.

[0037] (2) Take the mixed material out of the centrifugal mixer and disperse the mixture obtained by centrifugation in 100ml of deionized water to obtain a mixed solution.

[0038] (3) Add 0.03 g PVP to the mixture and stir at 300 rpm for 1 h on a magnetic stirrer.

[0039] (4) Add the mixture collected in step (3) to the spray dryer, adjust the air inlet temperature to 120 ℃ and the peristaltic pump feed rate to 100 mL / min until the machine can spray out powder evenly and continuously and collect the sprayed powder to obtain a lithium-ion battery negative electrode material derived from natural graphite and artificial graphite with spray drying assistance, denoted as AG:NG=7:3.

[0040] The SEM test results of the final product are as follows: Figure 1 As shown, flake-like natural graphite material surrounds block-like artificial graphite, indicating that PVP plays a certain role in bonding the two materials. Furthermore, spray granulation achieves a uniform distribution of natural and artificial graphite. The XRD test results of the final product are shown below. Figure 5 As shown, it exhibits a high-intensity (002) peak at 26.4°, indicating a high degree of graphitization in the final product; the Raman test results of the final product are as follows. Figure 6 As shown, the ID / IG value of the final product is smaller than that of natural graphite, indicating that the degree of defects on its surface is lower.

[0041] The electrochemical performance test results of the final product are as follows: Figure 7 , 8As shown in Figures 9, 10, and 11, the results indicate that the final product has a first-week charging capacity of 393.4 mAh / g and a first-week coulombic efficiency of 67.9%. Regarding long-term cycling performance, the final product retains a capacity of 311.2 mAh / g after 550 cycles at a current density of 1C, with a capacity retention of 87.6%. In terms of electrochemical impedance spectroscopy, the final product exhibits high RE after the first week, 10 cycles, and 100 cycles. SEI The values ​​are 69.0 Ω, 50.6 Ω, and 6.8 Ω, respectively. ct They are 132.0 Ω, 83.3 Ω, and 34.5 Ω, respectively; EDS diagram of the electrode plates of the battery assembled from the final product after cycling is shown in the figure. Figure 12 As shown, after charge-discharge cycles, the surface of the composite modified electrode remains intact with no obvious exposed copper foil area. This is because the composite modification increases the adhesion between material particles, which in turn helps maintain the stability of the electrode structure during cycling.

[0042] Example 2 (1) Weigh 0.5g of natural graphite with a particle size of 100 mesh and 0.5g of artificial graphite with a particle size of 100 mesh respectively, and centrifuge them in a centrifuge mixer at a speed of 3000 rpm for 5 minutes.

[0043] (2) Take the mixed material out of the centrifugal mixer and disperse the mixture obtained by centrifugation in 100ml of deionized water to obtain a mixed solution.

[0044] (3) Add 0.03 g PVP to the mixture and stir at 300 rpm for 1 h on a magnetic stirrer.

[0045] (4) Add the mixture collected in step (3) to the spray dryer, adjust the air inlet temperature to 120 ℃ and the peristaltic pump feed rate to 100 mL / min until the machine can spray out powder evenly and continuously and collect the sprayed powder to obtain a lithium-ion battery negative electrode material derived from natural graphite and artificial graphite with spray drying assistance, denoted as AG:NG=5:5.

[0046] The SEM test results of the final product are as follows: Figure 2 As shown, flake-like natural graphite material surrounds block-like artificial graphite, with both materials evenly distributed; the XRD test results of the final product are as follows. Figure 5 As shown, it has a high-intensity (002) peak, indicating that the final product has a high degree of graphitization; the Raman test results of the final product are as follows. Figure 6 As shown, its ID / IG value is less than that of natural graphite, indicating that the degree of surface defects is relatively low, suggesting that PVP pyrolysis covers a portion of the surface defects.

[0047] The electrochemical performance test results of the final product are as follows: Figure 7 , 8 As shown in Figures 9, 10, and 11, the results indicate that the final product has a first-week charging capacity of 385.0 mAh / g and a first-week coulombic efficiency of 68%. Regarding long-term cycling performance, the final product retains a capacity of 360.7 mAh / g after 550 cycles at a current density of 1C, with a capacity retention of 98.4%. As for electrochemical impedance spectroscopy, the final product exhibits high RE after the first week, 10 cycles, and 100 cycles. SEI The values ​​are 54.8 Ω, 8.1 Ω, and 5.2 Ω, respectively. ct The values ​​are 103.5 Ω, 27.8 Ω, and 26.8 Ω, respectively.

[0048] EDS diagram of the electrode plates of the battery assembled from the final product after cycling is shown in the figure. Figure 13 As shown, after charge-discharge cycles, the surface of the composite modified electrode remains intact, with no obvious exposed copper foil area.

[0049] Example 3 (1) Weigh 0.7g of natural graphite with a particle size of 100 mesh and 0.3g of artificial graphite with a particle size of 100 mesh respectively, and centrifuge them in a centrifuge mixer at a speed of 3000 rpm for 5 minutes.

[0050] (2) Take the mixed material out of the centrifugal mixer and disperse the mixture obtained by centrifugation in 100ml of deionized water to obtain a mixed solution.

[0051] (3) Add 0.03 g PVP to the mixture and stir at 300 rpm for 1 h on a magnetic stirrer.

[0052] (4) Add the mixture collected in step (3) to the spray dryer, adjust the air inlet temperature to 120 ℃ and the peristaltic pump feed rate to 100 mL / min until the machine can spray out powder evenly and continuously and collect the sprayed powder to obtain a lithium-ion battery negative electrode material derived from natural graphite and artificial graphite with spray drying assistance, denoted as AG:NG=3:7.

[0053] The SEM test results of the final product are as follows: Figure 3 As shown, flake-like natural graphite material surrounds block-like artificial graphite, with both materials evenly distributed; the XRD test results of the final product are as follows. Figure 5 As shown, it has a high-intensity (002) peak, indicating that the final product has a high degree of graphitization; the Raman test results of the final product are as follows. Figure 6 As shown, it has the smallest ID / IG value, indicating that its surface has the lowest degree of defects.

[0054] The electrochemical performance test results of the final product are as follows: Figure 7 , 8 As shown in Figures 9, 10, and 11, the results indicate that the final product has a first-week charging capacity of 362.6 mAh / g and a first-week coulombic efficiency of 67.2%. Regarding long-term cycling performance, the final product retains a capacity of 281.2 mAh / g after 550 cycles at a current density of 1C, with a capacity retention of 96.3%. In terms of electrochemical impedance spectroscopy, the final product exhibits high RE after the first week, 10 cycles, and 100 cycles. SEI The values ​​are 148.4 Ω, 59.4 Ω, and 21.1 Ω, respectively. ct The values ​​are 162.2 Ω, 103.2 Ω, and 46.6 Ω, respectively.

[0055] EDS diagram of the electrode plates of the battery assembled from the final product after cycling is shown in the figure. Figure 14 As shown, after charge-discharge cycles, the surface of the composite modified electrode remains intact, with no obvious exposed copper foil area.

[0056] Comparative Example 1 (1) Weigh 1g of natural graphite with a particle size of 100 mesh, disperse it in 100ml of deionized water to obtain a mixture.

[0057] (2) Add 0.03 g PVP to the mixture and stir at 300 rpm for 1 h on a magnetic stirrer.

[0058] (3) Add the mixture collected in step (2) to the spray dryer, adjust the air inlet temperature to 120 ℃ and the peristaltic pump feed rate to 100 mL / min until the machine can spray out powder evenly and continuously and collect the sprayed powder to obtain a spray drying-assisted natural graphite anode material, denoted as AG:NG=0:10.

[0059] The SEM test results of the final product are as follows: Figure 4 As shown, natural graphite has a relatively flat, lamellar structure; the XRD test results of the final product are as follows. Figure 5 As shown, a high-intensity (002) peak is present at 26.4°, indicating a high degree of graphitization; the Raman test results of the final product are as follows. Figure 6 As shown, its ID / IG value is 0.33, which is higher than that of other materials, indicating that its surface has a high degree of defects.

[0060] The electrochemical performance test results of the final product are as follows: Figure 7 , 8As shown in Figures 9, 10, and 11, the results indicate that the final product has a first-week charging capacity of 402.6 mAh / g and a first-week coulombic efficiency of 70.2%. Regarding long-term cycling performance, the capacity of the natural graphite bulk material significantly decreases after more than 200 cycles. The final product has a capacity of only 123.7 mAh / g after 550 cycles at a current density of 1C, with a capacity retention of only 33.8%. In terms of electrochemical impedance spectroscopy, the final product exhibits high Rt after the first week, 10 weeks, and 100 weeks. SEI The Ω values ​​are 65.4 Ω, 31.3 Ω, and 8.1 Ω, respectively, and the Rct values ​​are 302.5 Ω, 109.7 Ω, and 84.8 Ω, respectively. EDS diagram of the electrode plates of the battery assembled from the final product after cycling is shown in the figure. Figure 15 As shown, after charge-discharge cycles, “voids” appeared on the surface of the natural graphite electrode. EDS test results show that the “void” areas correspond to the exposed copper foil.

[0061] Comparative Example 2 (1) Weigh 1g of artificial graphite with a particle size of 100 mesh, disperse it in 100ml of deionized water to obtain a mixture.

[0062] (2) Add 0.03 g PVP to the mixture and stir at 300 rpm for 1 h on a magnetic stirrer.

[0063] (3) Add the mixture collected in step (2) to the spray dryer, adjust the air inlet temperature to 120 ℃, the peristaltic pump feed rate to 100 mL / min and other parameters until the machine can spray out powder evenly and continuously and collect the sprayed powder to obtain a spray-drying assisted artificial graphite anode material, denoted as AG:NG=10:0.

[0064] The XRD test results of the final product are as follows: Figure 5 As shown, it has high-intensity (100) and (101) peaks, indicating a high degree of graphitization; the Raman test results of the final product are as follows. Figure 6 As shown, its ID / IG value is only 0.09, indicating that the degree of surface defects is low.

[0065] The electrochemical performance test results of the final product are as follows: Figure 7 , 8 As shown in Figures 9, 10, and 11, the results indicate that the final product has a first-week charging capacity of 355.3 mAh / g and a first-week coulombic efficiency of 67.9%. Regarding long-term cycling performance, the final product's capacity significantly decreases after more than 200 cycles, reaching only 183.1 mAh / g after 550 cycles at 1C, with a capacity retention of only 47.9%. In terms of electrochemical impedance spectroscopy, the final product exhibits lower Rt values ​​after the first week, 10 weeks, and 100 weeks.SEI The Ω values ​​are 100.8 Ω, 59.4 Ω and 21.1 Ω respectively, and the Rct values ​​are 105.7 Ω, 18.7 Ω and 36.7 Ω respectively.

[0066] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite, characterized in that: The method steps include: Natural graphite and artificial graphite are centrifuged together to obtain mixed graphite; the mass ratio of natural graphite to artificial graphite is 3:7 to 7:

3. (2) Disperse the mixed graphite in deionized water to obtain a mixed graphite dispersion; (3) Add polyvinylpyrrolidone (PVP) to the mixed graphite dispersion and stir magnetically to obtain a mixture; the mass ratio of PVP to mixed graphite is 0.03:1~0.05:1; (4) Add the mixture to a spray dryer for spray drying. The inlet temperature is 110~130℃ and the feed rate is 80mL / min~150mL / min. Collect the sprayed powder to obtain a negative electrode material derived from natural graphite and artificial graphite composite.

2. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (1), the mass ratio of natural graphite to artificial graphite is 4:6 to 6:

4.

3. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (1), the particle size of the natural graphite and the artificial graphite is 100~300 mesh, respectively.

4. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (1), the speed of the centrifugal mixer is 2500~3000 rpm.

5. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (1), the centrifugal mixing time is 5~10 min.

6. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (2), the mass concentration of the mixed graphite dispersion is 8~10 g / L.

7. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (3), the rotation speed of the magnetic stirrer is 300~350 rpm.

8. The method for preparing a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 1, characterized in that: In step (3), the stirring time is 1~1.5 h.

9. A negative electrode material derived from a composite of natural graphite and artificial graphite, characterized in that: It is prepared by the method described in any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that: The negative electrode material of the battery is a negative electrode material derived from a composite of natural graphite and artificial graphite as described in claim 9.

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