Preparation method and application of fast-charging lithium battery graphite-based negative electrode
Patent Information
- Application Number
- CN202510555276.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2026-09-15
- Estimated Expiration
- 2045-04-29
AI Technical Summary
[0004]本发明的目的是要解决现有锂离子电池的快充负极材料存在倍率低，充放电性能差，能量密度较低，难以满足某些场合对快速补能以及大功率放电的需求的问题，而提供一种快充锂电池石墨基负极的制备方法和应用
[0014] I. This invention utilizes a ball milling process involving a mixture of graphite and hard carbon to assist in the exfoliation of the graphite layer through the mechanical shearing action of hard carbon particles, forming a composite structure of graphene and hard carbon. The introduction of hard carbon not only promotes efficient graphite exfoliation but also optimizes the conductive network and lithium-ion diffusion path of the composite material through its disordered porous characteristics. The graphite-based anode for fast-charging lithium batteries prepared by this invention exhibits high-rate charge-discharge performance and ultra-long cycle stability. After 3000 cycles under 10C high-current charge-discharge conditions, the capacity retention rate reaches as high as 83.3%, and after approximately 150 cycles of high-current activation, its rate performance is further significantly improved.
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Figure CN120432491B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing and applying a fast-charging composite negative electrode material for lithium batteries. Background Technology
[0002] With the deepening of global energy structure transformation and the concept of sustainable development, electric vehicles, energy storage systems, mobile devices, and the low-altitude economy have experienced rapid development. At the same time, these applications place higher performance demands on lithium-ion batteries, especially in terms of fast charging capability, energy density, and cycle life. While traditional graphite anode materials possess high reversible capacity and stability, their slow lithium-ion insertion and extraction kinetics limit high-rate charge and discharge performance, making it difficult to meet the needs of rapid energy replenishment and high-power discharge in certain applications.
[0003] Hard carbon, as an amorphous carbon material, possesses a large specific surface area and abundant lithium intercalation channels, enabling it to provide excellent rate performance and a wide lithium intercalation voltage range. However, the poor cycle life and low energy density of hard carbon limit its practical application as a standalone fast-charging anode material. Summary of the Invention
[0004] The purpose of this invention is to address the problems of existing fast-charging anode materials for lithium-ion batteries, such as low rate capability, poor charge-discharge performance, and low energy density, which make it difficult to meet the requirements of rapid energy replenishment and high-power discharge in certain applications. The invention provides a method for preparing and applying a graphite-based anode for fast-charging lithium batteries.
[0005] This invention presents a composite anode material that organically combines graphite and hard carbon. This material maintains the high reversible capacity and stable cycle performance of graphite while fully leveraging the fast-charging characteristics of hard carbon. This makes the development of lithium-ion batteries with both high energy density and fast-charging capabilities an important direction in the research of lithium-ion battery anode materials.
[0006] This invention, through innovative design, optimizes the graphite-hard carbon ratio in the composite material, improves its microstructure and interfacial properties, optimizes reaction kinetics, and achieves synergistic enhancement of the performance of the two materials. This material can not only significantly improve the fast charging capability of lithium-ion batteries, but also extend battery life while maintaining high energy density, thus paving the way for the development of high-performance lithium batteries.
[0007] A method for preparing a graphite-based anode for a fast-charging lithium battery, specifically comprising the following steps:
[0008] I. Preparation of graphite-hard carbon composite materials:
[0009] Graphite and hard carbon powder are placed in a ball mill jar, grinding balls are added to the ball mill jar, and the mixture is milled for a period of time to obtain a graphite-hard carbon composite material.
[0010] II. Electrode Preparation:
[0011] Graphite-hard carbon composite material, conductive carbon black Super P and PVDF powder are mixed evenly and ground for a period of time to obtain electrode powder; N-methylpyrrolidone is added to the electrode powder and stirred for a period of time to obtain electrode slurry; the electrode slurry is evenly coated on copper foil, then pre-baked for a period of time, and then placed in a vacuum oven for further drying to obtain graphite-based negative electrode for fast-charging lithium battery.
[0012] A graphite-based anode for fast-charging lithium batteries is used in lithium batteries.
[0013] The principles and advantages of this invention:
[0014] I. This invention utilizes a ball milling process involving a mixture of graphite and hard carbon to assist in the exfoliation of the graphite layer through the mechanical shearing action of hard carbon particles, forming a composite structure of graphene and hard carbon. The introduction of hard carbon not only promotes efficient graphite exfoliation but also optimizes the conductive network and lithium-ion diffusion path of the composite material through its disordered porous characteristics. The graphite-based anode for fast-charging lithium batteries prepared by this invention exhibits high-rate charge-discharge performance and ultra-long cycle stability. After 3000 cycles under 10C high-current charge-discharge conditions, the capacity retention rate reaches as high as 83.3%, and after approximately 150 cycles of high-current activation, its rate performance is further significantly improved.
[0015] Second, this invention solves the problems of easy lithium deposition and rapid capacity decay of traditional graphite anodes at high rates, while avoiding the defects of high cost and complex process of single graphene material preparation. It is suitable for fields with strict requirements for fast charging performance, such as electric vehicles and high-power energy storage devices. Attached Figure Description
[0016] Figure 1 SEM images of the negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown. In the figures, a represents Gr-bm, b represents Gr75, c represents Gr50, d represents Gr25, and e represents HC-bm.
[0017] Figure 2 The mass of graphene separated from four graphene solutions with different mass fractions;
[0018] Figure 3 Raman spectra of the negative electrode materials prepared in Example 1 and Comparative Examples 1-2;
[0019] Figure 4 The XRD spectra of the negative electrode materials prepared in Example 1 and Comparative Examples 1-2 are shown below.
[0020] Figure 5 SEM images of the negative electrode material prepared in Example 1 at different magnifications;
[0021] Figure 6The nitrogen adsorption isotherms of the negative electrode materials prepared in Example 1 and Comparative Examples 1-2 are shown.
[0022] Figure 7 The chart shows a comparison of the rate performance of lithium-ion half-cells assembled using Gr25, Gr50, G75, HC-bm, and Gr-bm, respectively, with 1C = 300 mAg. -1 ;
[0023] Figure 8 The lithium-ion diffusion coefficients are those of lithium-ion half-cells assembled using Gr25, HC-bm, and Gr-bm, respectively.
[0024] Figure 9 The graph shows a comparison of the high-rate cycle performance of lithium-ion half-cells assembled using Gr25, HC-bm, and Gr-bm, respectively, with 1C = 300 mAg. -1 ;
[0025] Figure 10 A comparison of the rate performance of lithium-ion half-cells assembled using Gr25 before and after high-current activation.
[0026] Figure 11 A comparison chart of the rate performance of a lithium-ion half-cell assembled using Gr25 and a lithium-ion half-cell assembled using commercial graphite anodes.
[0027] Figure 12 The rate performance of the lithium-ion half-cell assembled using GP25 prepared in Comparative Example 3 is shown in the graph.
[0028] Figure 13 The rate performance of the lithium-ion half-cell assembled using the GP prepared in Comparative Example 4 is shown in the graph.
[0029] Figure 14 The rate performance graph shows the lithium-ion half-cell assembled using Gr25 prepared in Example 1.
[0030] Figure 15 The rate performance of a lithium-ion half-cell assembled using Gr25 prepared in Example 1 after approximately 150 cycles at a high current (5C).
[0031] Figure 16 The graphs show the rate performance of a lithium-ion half-cell assembled using Gr25 prepared in Example 1, a lithium-ion half-cell assembled using Gr25 prepared in Example 1 after high-current activation, a lithium-ion half-cell assembled using GP25 prepared in Comparative Example 3, and a lithium-ion half-cell assembled using GP prepared in Comparative Example 4 at different rates. Detailed Implementation
[0032] Specific Implementation Method 1: This implementation method provides a method for preparing a graphite-based negative electrode for a fast-charging lithium battery, which is specifically completed according to the following steps:
[0033] I. Preparation of graphite-hard carbon composite materials:
[0034] Graphite and hard carbon powder are placed in a ball mill jar, grinding balls are added to the ball mill jar, and the mixture is milled for a period of time to obtain a graphite-hard carbon composite material.
[0035] II. Electrode Preparation:
[0036] Graphite-hard carbon composite material, conductive carbon black Super P and PVDF powder are mixed evenly and ground for a period of time to obtain electrode powder; N-methylpyrrolidone is added to the electrode powder and stirred for a period of time to obtain electrode slurry; the electrode slurry is evenly coated on copper foil, then pre-baked for a period of time, and then placed in a vacuum oven for further drying to obtain graphite-based negative electrode for fast-charging lithium battery.
[0037] The hard carbon powder mentioned in step one of this embodiment was purchased from Foshan Perls Carbon Materials Technology Co., Ltd., and its model is Kuraray Hard Carbon Type 1.
[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass fraction of graphite in the graphite-hard carbon composite material described in step one is 25% to 75%. The other steps are the same as in Specific Implementation Method One.
[0039] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the grinding ball in step one is made of zirconium oxide; the diameter of the grinding ball is one of 2mm and 5mm or a mixture of two diameters. The other steps are the same as in Specific Implementation Method One or Two.
[0040] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the ball milling speed in step one is 500 rpm to 700 rpm, and the ball milling time is 20 min to 40 min; the ball-to-material ratio in the ball milling process in step one is (5 to 15):1. Other steps are the same as in Specific Implementation Methods One to Three.
[0041] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the mass ratio of the graphite-hard carbon composite material, conductive carbon black Super P, PVDF powder, and N-methylpyrrolidone in step two is (0.3g~0.5g):(0.03g~0.08g):(0.03g~0.08g):(1.5g~2.5g). The other steps are the same as in Specific Implementation Methods One to Four.
[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the grinding time in step two is 10 to 20 minutes; the stirring speed in step two is 200 rpm to 800 rpm, and the stirring time is 4 to 8 hours. The other steps are the same as in Specific Implementation Methods One to Five.
[0043] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One to Six is that in step two, the electrode paste is uniformly coated on the copper foil with a coating thickness of 50μm to 200μm, and then pre-baked at 60℃ to 100℃ for 1h to 5h, and then placed in a vacuum oven at 80℃ to 150℃ for 10 to 20h to obtain the electrode.
[0044] The other steps are the same as those in Specific Implementation Methods 1 to 6.
[0045] Specific implementation method eight: This implementation method is an application of graphite-based negative electrode in fast-charging lithium batteries.
[0046] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that: the assembly of a lithium battery using a fast-charging lithium battery graphite-based negative electrode is specifically completed according to the following steps:
[0047] The graphite-based negative electrode of a fast-charging lithium battery is cut into 12mm diameter sheets using a stamping machine to obtain the negative electrode sheet. In a glove box under an argon atmosphere, the negative electrode battery casing, spring sheet, gasket, lithium sheet, PP separator, negative electrode sheet, and positive electrode battery casing are stacked in the following order: negative electrode battery casing, spring sheet, gasket, lithium sheet, PP separator, negative electrode sheet, and positive electrode battery casing. The lithium sheet and negative electrode sheet have a diameter of 12mm, and the separator has a diameter of 19mm. 50μL of electrolyte is dropped onto each side of the separator. After sealing with a button battery sealing machine, a lithium-ion half-cell is obtained. The electrolyte is a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, with LiPF6 as the solvent and a LiPF6 concentration of 1mol / L. Other steps are the same as in specific embodiments one through eight.
[0048] Specific Implementation Method Ten: The difference between this implementation method and Specific Implementation Methods One to Nine is that the lithium-ion half-cell is activated by a 1C to 10C current for 50 to 200 cycles, with a 1C current density of 300 mAg. -1 This yields a lithium-ion half-cell with excellent rate performance. The other steps are the same as in embodiments one through nine.
[0049] The beneficial effects of the present invention are verified using the following embodiments:
[0050] Example 1: A method for preparing a graphite-based anode for a fast-charging lithium battery, specifically comprising the following steps:
[0051] I. Preparation of graphite-hard carbon composite materials:
[0052] Graphite and hard carbon powder were placed in a ball mill jar, grinding balls were added to the jar, and the mixture was ball milled at 600 rpm for 30 minutes to obtain a graphite-hard carbon composite material.
[0053] The graphite-hard carbon composite material described in step one contains 25% graphite by mass.
[0054] The hard carbon powder mentioned in step one was purchased from Foshan Perls Carbon Materials Technology Co., Ltd., and the model is Kuraray hard carbon type 1.
[0055] The grinding balls mentioned in step one are made of zirconium oxide; the diameters of the grinding balls are 2mm and 5mm; the mass ratio of the grinding balls with a diameter of 2mm to the grinding balls with a diameter of 5mm is 1:1.
[0056] In the ball milling process described in step one, the ball-to-material ratio is 10:1;
[0057] II. Electrode Preparation:
[0058] 0.4g of graphite-hard carbon composite material, 0.05g of conductive carbon black Super P, and 0.05g of PVDF powder were mixed evenly and ground for 10min to obtain electrode powder. 2g of N-methylpyrrolidone was added to the electrode powder and stirred for 5h at 500rpm to obtain electrode slurry. The electrode slurry was evenly coated on copper foil with a coating thickness of 100μm, pre-baked at 80℃ for 2h, and then placed in a vacuum oven at 120℃ for 12h to continue drying to obtain graphite-based anode for fast-charging lithium batteries (denoted as Gr25).
[0059] Example 2: The difference between this example and Example 1 is that the graphite mass fraction in the graphite-hard carbon composite material described in step one is 50%; the graphite-based negative electrode of the fast-charging lithium battery obtained in step two is denoted as Gr50. All other steps and parameters are the same as in Example 1.
[0060] Example 3: The difference between this example and Example 1 is that the graphite mass fraction in the graphite-hard carbon composite material described in step one is 75%; the graphite-based negative electrode of the fast-charging lithium battery obtained in step two is denoted as Gr75. All other steps and parameters are the same as in Example 1.
[0061] Comparative Example 1: The difference between this embodiment and Example 1 is that the mass fraction of graphite in the graphite-hard carbon composite material described in step one is 0%; the hard carbon anode material obtained in step two is denoted as HC-bm. All other steps and parameters are the same as in Example 1.
[0062] Comparative Example 2: The difference between this embodiment and Example 1 is that the graphite mass fraction in the graphite-hard carbon composite material described in step one is 100%; the graphite anode material obtained in step two is denoted as Gr-bm. All other steps and parameters are the same as in Example 1.
[0063] Figure 1 SEM images of the negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown. In the figures, a represents Gr-bm, b represents Gr75, c represents Gr50, d represents Gr25, and e represents HC-bm.
[0064] from Figure 1 It can be seen that: almost all of the pure graphite after ball milling exhibits a large-block layered graphite structure. Figure 1 a), while ball-milled pure hard carbon exhibits a angular, blocky structure and pulverized hard carbon particles ( Figure 1 e) As the hard carbon content in the composite material increases ( Figure 1 (b-1d) It can be clearly seen that the size of the graphite particles gradually decreases, from large particles of more than 5 μm (Gr-bm) to small particles of about 3.5 μm and above (Gr75) and about 2.5 μm (Gr50); when the hard carbon content is increased to 75% (Gr25), the graphite is exfoliated into few-layer graphene of about 1 μm; indicating that hard carbon plays an important role in the exfoliation of graphene during the ball milling process of the mixed materials.
[0065] To quantify the graphene content extracted by ball milling at different ratios, four 0.5g portions of graphene were dissolved in four portions of anhydrous ethanol to prepare graphene solutions with mass fractions of 25%, 50%, 75%, and 100%, respectively, namely Gr25, Gr50, Gr75, and Grbm. First, the solutions were ultrasonically dispersed for 30 min, then centrifuged at 10000 rpm for 10 min. The supernatant contained unseparated graphene. The supernatants from the five samples were centrifuged a second time at the same speed for 1 h. After removing the supernatant from the second centrifugation, the solutions were dried and the precipitates were extracted. The mass of each of the five precipitates was measured. Although Gr25 had the lowest graphite content, it had the highest relative graphene content. Figure 2 As shown.
[0066] Figure 2 The mass of graphene separated from four graphene solutions with different mass fractions;
[0067] Figure 2 This demonstrates that by rationally designing the ball milling ratio of graphite and hard carbon, the exfoliation efficiency of graphene can be greatly improved.
[0068] Figure 3 Raman spectra of the negative electrode materials prepared in Example 1 and Comparative Examples 1-2;
[0069] from Figure 3 It can be determined that the location is at 1352cm. -1 (D belt) and 1580cm -1 The peaks in the (G band) belong to sp... 3 Type disorder and sp 2 HC-bm exhibits a strong D peak, indicating the presence of numerous defects in the material, consistent with the characteristics of hard carbon. Furthermore, compared to Gr-bm, Gr25 shows a larger peak intensity ratio between the D and G bands, suggesting the introduction of more defects and electrochemically active centers on the material surface; while the G' peak intensity of Gr25 is higher than that of Gr-bm, indicating the presence of few-layer graphene in Gr25, proving the successful exfoliation of graphene.
[0070] Figure 4 The XRD spectra of the negative electrode materials prepared in Example 1 and Comparative Examples 1-2 are shown below.
[0071] from Figure 4 It can be seen that Gr25 matches the characteristic peaks of Gr, preserving the basic crystal characteristics of graphite. The broadening of the 002 peak indicates that Gr25 has a higher degree of disorder than Gr-bm; in addition, the decrease in the intensity of the 002 peak suggests that Gr25 may have a smaller grain size. Combined with the fact that the G' peak in the Raman spectrum matches the characteristics of few-layer graphene, this further proves the existence of graphene.
[0072] Figure 5 SEM images of the negative electrode material prepared in Example 1 at different magnifications;
[0073] from Figure 5 As can be seen in sample a, a large amount of few-layer graphene is present. Figure 5 b shows that graphene is tightly distributed around the bulk hard carbon, which can improve surface roughness, increase the sample surface area, and provide space for lithium ions; the uniform distribution of graphene on hard carbon also promotes uniform lithium intercalation during fast charging. (High-magnification TEM) Figure 5 As can be clearly seen in c), Gr has a uniform sheet-like crystal structure, while HC exhibits a unique amorphous structure. Gr25, on the other hand, shows graphite tightly embedded in hard carbon. The unique structure composed of hard carbon and exfoliated few-layer graphene can effectively enhance the mass transfer performance of lithium ions, thereby improving the surface's lithiophilicity, reducing the occurrence of dead lithium, and improving fast-charging performance.
[0074] Figure 6 The nitrogen adsorption isotherms of the negative electrode materials prepared in Example 1 and Comparative Examples 1-2 are shown.
[0075] from Figure 6 It can be seen that Gr25 has the largest specific surface area, at 22.9551 m², due to its unique structure. 2 g -1HC-bm and Gr-bm exhibit a blocky structure with a relatively small surface area of 19.8289 m². 2 g -1 and 10.5598m 2 g -1 The presence of graphene in Gr25 determines its large specific surface area, demonstrating the superiority of the Gr25 structural design.
[0076] Assembling a lithium-ion half-cell is done in the following steps:
[0077] The graphite-based negative electrode (Gr25) of the fast-charging lithium battery prepared in Example 1 was cut into electrode sheets with a diameter of 12 mm using a punching machine to obtain negative electrode sheets. In a glove box under an argon atmosphere, the negative electrode battery shell, spring sheet, gasket, lithium sheet, PP separator, negative electrode sheet, and positive electrode battery shell were stacked in that order. The diameter of the lithium sheet and negative electrode sheet was 12 mm, and the diameter of the separator was 19 mm. 50 μL of electrolyte was dropped onto both sides of the separator. After sealing with a button battery sealing machine, a lithium-ion half-cell was obtained. The electrolyte was a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, with LiPF6 as the solvent and a concentration of 1 mol / L.
[0078] Following the above method, Gr50, G75, HC-bm, and Gr-bm were cut into electrode sheets with a diameter of 12mm, and then assembled into lithium-ion half-cells.
[0079] Rate performance of lithium-ion half-cells assembled with five different materials was tested. (See attached image.) Figure 7 As shown;
[0080] Figure 7 The chart shows a comparison of the rate performance of lithium-ion half-cells assembled using Gr25, Gr50, G75, HC-bm, and Gr-bm, respectively, with 1C = 300 mAg. -1 ;
[0081] from Figure 7 It can be seen that at 0.2C, Gr-bm has a much higher specific capacity than HC-bm, indicating that graphite has a higher energy density; while at 10C, HC-bm has a much higher specific capacity than Gr-bm, indicating that hard carbon has better rate performance. After ball milling the two materials together, Gr25 showed a higher energy density (292.7 mAh g⁻¹ at 0.2C). -1 Slightly lower than Gr bm324.4mAh g -1 This is significantly higher than HC bm: 197.2mAh g -1 ) and excellent rate performance (10C 123.3mAh g) -1Even better than HC bm: 107.5mAh g -1 Far exceeding Gr bm: 25mAh g -1 Furthermore, compared to the other two materials with different proportions, Gr50 and Gr75, it exhibits a significant advantage in capacity under high current, demonstrating its excellent overall performance. By rationally designing the composite ratio of graphite and hard carbon, the respective advantages of graphite and hard carbon can be fully utilized, achieving a good synergistic effect between them.
[0082] The lithium-ion diffusion coefficients of three half-cells were tested using GITT. Figure 8 As shown;
[0083] Figure 8 The lithium-ion diffusion coefficients are those of lithium-ion half-cells assembled using Gr25, HC-bm, and Gr-bm, respectively.
[0084] from Figure 8 It can be seen that Gr25 has the main lithium storage potential in graphite (plateau region: approximately 0.01–0.2V vs. Li / Li). + The lithium-ion diffusion coefficient of ) is significantly better than that of Gr-bm, while the lithium storage potential of hard carbon (slope region: >0.05V vs. Li / Li) is higher. + At most potentials, Gr25 exhibits a superior lithium-ion diffusion coefficient compared to HC-bm. This advantage in lithium-ion diffusion coefficient across various potentials contributes to Gr25's excellent rate performance.
[0085] The cycle performance of lithium-ion half-cells assembled using Gr-bm, Gr25, and HC-bm was tested at a high current of 10C. Figure 9 As shown;
[0086] Figure 9 The graph shows a comparison of the high-rate cycle performance of lithium-ion half-cells assembled using Gr25, HC-bm, and Gr-bm, respectively, with 1C = 300 mAg. -1 ;
[0087] from Figure 9 It can be seen that Gr-bm has poor rate performance, with its capacity dropping to 43.5% of its maximum capacity after about 1500 cycles. Even HC-bm, which has better rate performance, drops to 80% of its maximum capacity after about 1440 cycles. Gr25, on the other hand, exhibits excellent high-rate cycling performance. After 3000 cycles at 10C, the remaining capacity is still 83.3% of its maximum capacity, demonstrating Gr25's excellent high-current cycling performance.
[0088] The rate performance of lithium-ion half-cells assembled using Gr25 was further improved after approximately 150 cycles at a relatively high current (5C). Figure 10 As shown.
[0089] Figure 10 A comparison of the rate performance of lithium-ion half-cells assembled using Gr25 before and after high-current activation.
[0090] Figure 10 Rate performance of lithium-ion half-cells assembled using Gr25 at different rates;
[0091] from Figure 10 It can be seen that after high-current cycling, the 10C capacity decreased from 123mAh g. -1 Upgraded to 164mAh g -1 Increased by 41mAh g -1 The most significant capacity increase is seen in the 5C version, which has increased from 140mAh. -1 Upgraded to 228mAh g -1 Increased by 88mAh g -1 This indicates that high-current activation significantly enhances the rate performance of Gr25.
[0092] To verify the practical application potential of Gr25 materials, a high-load Gr25 electrode (~9 mg cm⁻¹) with the same active material loading as commercial graphite anodes was prepared. -2 ), and conducted rate performance testing, see Figure 11 As shown;
[0093] Figure 11 A comparison chart of the rate performance of a lithium-ion half-cell assembled using Gr25 and a lithium-ion half-cell assembled using commercial graphite anodes.
[0094] from Figure 11 It can be seen that at 0.2C, due to the large theoretical capacity of graphite, the specific capacity of commercial graphite electrodes is relatively high. When the current density is increased to 1C and above, Gr25 exhibits a higher specific capacity. This indicates that Gr25 has better rate performance than currently commercial graphite anodes at high loads, demonstrating great potential application value.
[0095] To verify the superiority of the graphite + hard carbon + graphene electrode material, a graphene + hard carbon anode material was prepared, as detailed below:
[0096] Comparative Example 3: The difference between this example and Example 1 is that the graphite in step one is replaced with graphene. The graphene is physical few-layer graphene purchased from Suzhou CarbonFeng Graphene Technology Co., Ltd.; the mass fraction of graphene in the graphene-hard carbon composite material obtained in step one is 25%; the negative electrode material obtained in step two is designated as GP25. Other steps and parameters are the same as in Example 1.
[0097] Comparative Example 4: The difference between this example and Example 1 is that the graphite in step one is replaced with graphene. The graphene is physical few-layer graphene purchased from Suzhou Carbon-Feng Graphene Technology Co., Ltd.; the mass fraction of graphene in the graphene-hard carbon composite material obtained in step one is 100%; the negative electrode material obtained in step two is denoted as GP. Other steps and parameters are the same as in Example 1.
[0098] Following the above method, GP25 and GP were cut into electrode sheets with a diameter of 12mm, and then assembled into lithium-ion half-cells.
[0099] Figure 12 The rate performance of the lithium-ion half-cell assembled using GP25 prepared in Comparative Example 3 is shown in the graph.
[0100] Figure 13 The rate performance of the lithium-ion half-cell assembled using the GP prepared in Comparative Example 4 is shown in the graph.
[0101] Figure 14 The rate performance graph shows the lithium-ion half-cell assembled using Gr25 prepared in Example 1.
[0102] Figure 15 The rate performance of a lithium-ion half-cell assembled using Gr25 prepared in Example 1 after approximately 150 cycles at a high current (5C).
[0103] from Figures 12-15 It can be seen that: Gr25's rate performance (10C 123.3mAh g) -1 ) outperforms GP and GP25 in rate performance (10C 7.5mAh g) -1 70mAh g -1 This indicates that electrode materials containing graphite, hard carbon, and graphene, fabricated using hard carbon-assisted graphite exfoliation, exhibit a significant rate performance improvement compared to pure graphene and graphene-hard carbon hybrid anodes. Furthermore, Gr25 demonstrates further improved rate performance (10C 164.2 mAh g⁻¹) after 150 cycles of high-current (5C) activation. -1 ).
[0104] The lithium-ion half-cell assembled using the Gr25 prepared in Example 1 was activated at a high current of 5C for 150 cycles, and its rate performance at different rates was then tested. (See attached table). Figure 16 The activated Gr25 curve is shown in the figure.
[0105] Figure 16The rate performance graphs are of the lithium-ion half-cell assembled using Gr25 prepared in Example 1, the lithium-ion half-cell assembled using Gr25 prepared in Example 1 after high current activation, the lithium-ion half-cell assembled using GP25 prepared in Comparative Example 3, and the lithium-ion half-cell assembled using GP prepared in Comparative Example 4 at different rates.
[0106] from Figure 16 It can be seen that the hard carbon-assisted exfoliation of graphite to produce graphene prepared by this invention has better rate performance than pure graphene and graphene-hard carbon mixture, and its performance is further improved after high current activation.
Claims
1. A method for preparing a graphite-based anode for a fast-charging lithium battery, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of graphite-hard carbon composite materials: Graphite and hard carbon powder are placed in a ball mill jar, grinding balls are added to the ball mill jar, and the mixture is milled for a period of time to obtain a graphite-hard carbon composite material. The graphite-hard carbon composite material described in step one has a graphite mass fraction of 25%. The ball milling speed in step one is 500 rpm to 700 rpm, and the ball milling time is 20 min to 40 min; In the ball milling process described in step one, the ball-to-material ratio is (5~15):1; II. Electrode Preparation: Graphite-hard carbon composite material, conductive carbon black Super P and PVDF powder are mixed evenly and ground for a period of time to obtain electrode powder; N-methylpyrrolidone is added to the electrode powder and stirred for a period of time to obtain electrode slurry; the electrode slurry is evenly coated on copper foil, then pre-baked for a period of time, and then placed in a vacuum oven to continue drying to obtain graphite-based negative electrode for fast-charging lithium battery. The mass ratio of the graphite-hard carbon composite material, conductive carbon black Super P, PVDF powder, and N-methylpyrrolidone mentioned in step two is (0.3g~0.5g):(0.03g~0.08g):(0.03g~0.08g):(1.5g~2.5g).
2. The preparation method of the fast-charging lithium battery graphite-based negative electrode according to claim 1, characterized in that The grinding balls mentioned in step one are made of zirconium oxide; the diameter of the grinding balls is one of 2 mm and 5 mm or a mixture of two diameters.
3. The method for preparing a graphite-based negative electrode for a fast-charging lithium battery according to claim 1, characterized in that... The grinding time in step two is 10 min to 20 min; the stirring speed in step two is 200 rpm to 800 rpm, and the stirring time is 4 h to 8 h.
4. The method for preparing a graphite-based negative electrode for a fast-charging lithium battery according to claim 1, characterized in that... In step two, the electrode paste is uniformly coated on the copper foil with a coating thickness of 50μm~200μm. Then, it is pre-baked at 60℃~100℃ for 1h~5h, and then placed in a vacuum oven at 80℃~150℃ for 10~20h to continue drying, thus obtaining the electrode.
5. The application of a graphite-based anode for a fast-charging lithium battery prepared by the method described in claim 1, characterized in that... A graphite-based anode for fast-charging lithium batteries is used in lithium batteries.
6. The application of a graphite-based negative electrode for a fast-charging lithium battery according to claim 5, characterized in that... The assembly of a lithium battery using a graphite-based anode for fast-charging lithium batteries is carried out in the following steps: The graphite-based negative electrode of a fast-charging lithium battery is cut into 12mm diameter sheets using a punching machine to obtain the negative electrode sheet. In a glove box under an argon atmosphere, the negative electrode battery casing, spring sheet, gasket, lithium sheet, PP separator, negative electrode sheet, and positive electrode battery casing are stacked in the following order: lithium sheet and negative electrode sheet, with a diameter of 12mm and a separator diameter of 19mm. 50μL of electrolyte is dropped onto both sides of the separator. After sealing with a button battery sealing machine, a lithium-ion half-cell is obtained. The electrolyte is a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, with LiPF6 as the solute and a concentration of 1mol / L.
7. The application of a graphite-based negative electrode for a fast-charging lithium battery according to claim 6, characterized in that... The lithium ion half battery is activated by 1C~10C current for 50 cycles~200 cycles, and the 1C current density is 300mAg -1 , and a lithium ion half battery with excellent rate performance is obtained.