Graphite anode material with in-situ grown onion carbon layer structure and its preparation method
By growing an onion-like carbon layer in situ on the surface of graphite particles, the structural damage and irreversible capacity increase caused by electrolyte embedding in graphite anode materials during charge and discharge are solved, achieving higher battery cycle performance and first-cycle efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LIYANG TIANMU PILOT BATTERY MATERIAL TECH CO LTD
- Filing Date
- 2021-07-20
- Publication Date
- 2026-08-04
AI Technical Summary
During the charging and discharging process, the graphite anode material suffers from pulverization and poor electrocycling performance due to the intercalation of polar molecules in the electrolyte, which leads to the destruction of the layer structure. Furthermore, the amorphous carbon coating increases the irreversible capacity.
An onion-like carbon layer was grown in situ on the surface of graphite particles. By controlling the growth process and atmosphere, an onion-like carbon layer with a thickness of 1 nm to 1000 nm was formed, which reduced the intercalation of polar molecules in the electrolyte, reduced the specific surface area, and facilitated the formation of the SEI film.
It significantly reduces irreversible capacity, improves first-cycle efficiency and battery cycle performance, and is suitable for liquid, semi-solid, quasi-solid, and all-solid lithium-ion batteries.
Smart Images
Figure CN115642252B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of materials technology, and in particular to a graphite anode material with an in-situ grown onion carbon layer structure and its preparation method. Background Technology
[0002] Graphite is currently the main anode material for lithium batteries, characterized by abundant resources, low price, and high reversible capacity.
[0003] However, the graphite layers in graphite materials are bound together by van der Waals forces, resulting in weak interlayer forces and small interlayer spacing. During charging and discharging, not only lithium ions but also polar molecules in the electrolyte can embed between the graphite layers, damaging the graphite layer structure, causing graphite flakes to peel off and pulverize, leading to unsatisfactory electrocycle performance. Summary of the Invention
[0004] This invention provides a graphite anode material with an in-situ grown onion-like carbon layer structure and its preparation method. By growing a complete onion-like carbon layer on the surface of graphite particles, the embedding of polar molecules in the electrolyte into the graphite layer is reduced. Compared to the currently commonly used method of coating amorphous carbon, the onion-like carbon layer grown on the surface of graphite particles has a smaller specific surface area. Furthermore, the commonly used amorphous carbon coating also increases surface impurities and functional groups. Although the amorphous carbon coating layer can prevent the embedding of polar molecules in the electrolyte, it also leads to an increase in irreversible capacity. However, by having the onion-like carbon layer contact the electrolyte, the formation of the solid electrolyte interphase (SEI) film is reduced. The resulting SEI film is thinner and more uniform, further reducing irreversible capacity.
[0005] In a first aspect, embodiments of the present invention provide a graphite anode material having an in-situ grown onion carbon layer structure, wherein the core of the graphite anode material is graphite material and the outer shell is an in-situ grown onion carbon layer, and the thickness of the onion carbon layer is 1 nm to 1000 nm.
[0006] The particle size range of the graphite anode material is 500 nm to 100 μm.
[0007] Secondly, embodiments of the present invention provide a method for preparing the graphite anode material with an in-situ grown onion carbon layer structure as described in the first aspect, the preparation method comprising:
[0008] A solution containing one or more elements of iron, cobalt, and nickel is mixed with a high carbon residue polymer, stirred evenly, dispersed, and dried to obtain dried granules; the high carbon residue polymer includes one or more combinations of asphalt, phenolic resin, or epoxy resin; the solution containing one or more elements of iron, cobalt, and nickel includes one or more of ferric nitrate solution, cobalt nitrate solution, and nickel nitrate solution.
[0009] The dried granules are mixed with graphite and granulated in a shaping machine; the mass ratio of the compound, the high carbon residue polymer, and the graphite is 1:0.5:1 to 1:5:100.
[0010] The granulated product is heated to 1000℃~1300℃ at a rate of 1℃ / min~10℃ / min under a protective atmosphere and held for 2 hours~15 hours. Then, the temperature is further increased to 2000℃~2500℃ and held for 1 hour~5 hours to obtain the graphite anode material with an in-situ grown onion carbon layer structure.
[0011] Preferably, the rotation speed of the shaping machine is 100 r / min to 1000 r / min, and the granulation time is 0.5 hours to 6 hours.
[0012] Preferably, the protective atmosphere is argon or nitrogen.
[0013] Preferably, the drying process includes any one of warm air drying, freeze drying, or spray drying.
[0014] Thirdly, embodiments of the present invention provide a negative electrode, comprising the graphite negative electrode material having an in-situ grown onion carbon layer structure as described in the first aspect above.
[0015] Fourthly, embodiments of the present invention provide a lithium battery, including the negative electrode described in the third aspect above.
[0016] The graphite anode material with an in-situ grown onion carbon layer structure provided in this invention transforms the external particles of the graphite material into an in-situ grown onion carbon layer. This onion carbon layer reduces the embedding of polar molecules from the electrolyte into the graphite layer. Compared to the currently commonly used method of coating amorphous carbon, the onion carbon layer grown on the surface of graphite particles has a smaller specific surface area. Furthermore, the commonly used amorphous carbon coating also increases surface impurities and functional groups. Although the amorphous carbon coating layer can prevent the embedding of polar molecules from the electrolyte, it also leads to an increase in irreversible capacity. However, by having the onion carbon layer contact the electrolyte, the formation of the solid electrolyte interphase (SEI) film is reduced, resulting in a thinner and more uniform SEI film, which further reduces irreversible capacity. The graphite anode material provided by this invention can be used in liquid, semi-solid, quasi-solid, and all-solid-state electrolyte lithium-ion batteries. Attached Figure Description
[0017] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples.
[0018] Figure 1 This is a schematic diagram of the graphite anode material with an in-situ grown onion carbon layer structure according to an embodiment of the present invention;
[0019] Figure 2 This is a flowchart illustrating a method for preparing a graphite anode material with an in-situ grown onion carbon layer structure according to an embodiment of the present invention.
[0020] Figure 3 Transmission electron microscope (TEM) image of the graphite anode material with an onion carbon layer structure provided in Embodiment 1 of the present invention;
[0021] Figure 4 This is a capacity cycle retention diagram of lithium-ion batteries prepared using graphite raw materials, graphite anode materials of Example 1 and Comparative Example 1, respectively. Detailed Implementation
[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.
[0023] The present invention relates to a graphite anode material with an in-situ grown onion-like carbon layer structure. For example... Figure 1 As shown, the core of the graphite anode material is graphite, and the outer shell is an in-situ grown onion carbon layer with a thickness of 1 nm to 1000 nm; the particle size of the graphite anode material ranges from 500 nm to 100 μm.
[0024] The above materials can be prepared in the following manner, with the main steps as follows: Figure 2 As shown, it includes:
[0025] Step 110: Mix a solution of a compound containing one or more of the elements iron, cobalt, and nickel with a high carbon residue polymer, stir until uniform, disperse and dry to obtain dried granules.
[0026] The high carbon residue polymer includes: one or more of asphalt, phenolic resin or epoxy resin; a solution containing one or more of the elements iron, cobalt or nickel, including one or more of the elements iron nitrate solution, cobalt nitrate solution, nickel nitrate solution, etc.; and the mass ratio of the compound containing one or more of the elements iron, cobalt or nickel to the high carbon residue polymer is 1:0.5 to 1:5.
[0027] Step 120: Mix the dried granules with graphite and granulate them in a shaping machine;
[0028] The mass ratio of the compound, high carbon residue polymer, and graphite is 1:0.5:1 to 1:5:100. The rotation speed of the shaping machine is 100 r / min to 1000 r / min, and the granulation time is 0.5 hours to 6 hours.
[0029] Step 130: The granulated product is heated to 1000℃~1300℃ at 1℃ / min~10℃ / min under a protective atmosphere and held for 2 hours~15 hours. Then, the temperature is further increased to 2000℃~2500℃ and held for 1 hour~5 hours to obtain a graphite anode material with an in-situ grown onion carbon layer structure.
[0030] Specifically, the protective atmosphere includes nitrogen, argon, or other inert atmospheres.
[0031] The above method transforms the external particles of graphite material into an in-situ grown onion-like carbon layer. This onion-like carbon layer reduces the embedding of polar molecules from the electrolyte into the graphite layer. Compared to the currently common method of coating amorphous carbon, the onion-like carbon layer grown on the surface of graphite particles has a smaller specific surface area. Furthermore, the commonly used amorphous carbon coating also increases surface impurities and functional groups. While the amorphous carbon coating can prevent the embedding of polar molecules from the electrolyte, it also leads to an increase in irreversible capacity. In contrast, by having the onion-like carbon layer contact the electrolyte, the formation of the SEI film is reduced, resulting in a thinner and more uniform SEI film, which further reduces irreversible capacity. The graphite anode material provided by this invention can be used in liquid, semi-solid, quasi-solid, and all-solid-state electrolyte lithium-ion batteries.
[0032] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing graphite anode materials using the method provided in the above embodiments of the present invention, and the characteristics of applying them to lithium-ion batteries.
[0033] Example 1
[0034] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0035] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 100mL of distilled water, add 50g of phenolic resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dried particles with D50 = 7.5um.
[0036] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 100r / min for 0.5 hours.
[0037] The granulated product was heated to 1000℃ at 1℃ / min in an argon atmosphere and held for 2 hours. Then, it was further heated to 2000℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0038] Figure 3This is a TEM image of the graphite anode material with an onion-like carbon layer structure provided in Embodiment 1 of the present invention.
[0039] To facilitate a better comparison, we prepared the comparison samples using the following method.
[0040] Comparative Example 1
[0041] Weigh 100g of graphite particles with D50=5.2um, mix them with 50g of phenolic resin, and add them to a granulator for granulation at a speed of 100r / min for 0.5 hours.
[0042] The granulated product was heated to 1000℃ at 1℃ / min in an argon atmosphere and held for 2 hours. Then, it was further heated to 2000℃ and held for 1 hour to obtain the comparative graphite anode material.
[0043] Example 2
[0044] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0045] Weigh 10g of ferric nitrate nonahydrate, dissolve it in 500mL of distilled water, add 500g of phenolic resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dried particles with D50=6.3um.
[0046] Weigh 1000g of graphite particles with D50 = 5.8um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 1000r / min for 6 hours.
[0047] The granulated product was heated to 1000℃ at 10℃ / min in an argon atmosphere and held for 15 hours. Then, it was further heated to 2000℃ and held for 5 hours to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0048] Example 3
[0049] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0050] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 100mL of distilled water, add 100g of asphalt, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dry particles with D50 = 3.5um.
[0051] Weigh 100g of graphite particles with D50 = 7.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 1000r / min for 2 hours.
[0052] The granulated product was heated to 1300℃ at 1℃ / min under nitrogen atmosphere, held for 2 hours, and then further heated to 2500℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0053] Example 4
[0054] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0055] Weigh 100g of nickel nitrate hexahydrate, dissolve it in 100mL of distilled water, add 50g of phenolic resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dry particles with D50=8.5um.
[0056] Weigh 1000g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 1000r / min for 6 hours.
[0057] The granulated product was heated to 1300℃ at 5℃ / min under nitrogen atmosphere and held for 6 hours. Then, the temperature was further increased to 2500℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0058] Example 5
[0059] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0060] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 100mL of distilled water, add 200g of epoxy resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dried particles with D50 = 8.9um.
[0061] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 500r / min for 5 hours.
[0062] The granulated product was heated to 1000℃ at 3℃ / min under nitrogen atmosphere and held for 5 hours. Then, the temperature was further increased to 2500℃ and held for 2 hours to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0063] Example 6
[0064] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0065] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 100mL of distilled water, add 200g of epoxy resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dried particles with D50 = 8.9um.
[0066] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 500r / min for 5 hours.
[0067] The granulated product was heated to 1200℃ at 3℃ / min under nitrogen atmosphere and held for 2 hours. Then, it was further heated to 2000℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0068] Example 7
[0069] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0070] Weigh 100g of nickel sulfate hexahydrate, add 100mL of distilled water to dissolve it, add 200g of epoxy resin and stir evenly for ultrasonic dispersion, then dry at 80℃ for 10 hours to obtain dried particles with D50=8.5um.
[0071] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 1000r / min for 0.5 hours.
[0072] The granulated product was heated to 1200℃ at 1℃ / min under nitrogen atmosphere, held for 2 hours, and then further heated to 2500℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0073] Example 8
[0074] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0075] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 100mL of distilled water, add 200g of phenolic resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dried particles with D50 = 6.3um.
[0076] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 1000r / min for 0.5 hours.
[0077] The granulated product was heated to 1200℃ at 1℃ / min under nitrogen atmosphere, held for 2 hours, and then further heated to 2500℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0078] Example 9
[0079] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0080] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 100mL of distilled water, add 50g of asphalt, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dry particles with D50 = 6.5um.
[0081] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 100r / min for 0.5 hours.
[0082] The granulated product was heated to 1000℃ at 1℃ / min under nitrogen atmosphere and held for 2 hours. Then, it was further heated to 2000℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0083] Example 10
[0084] This embodiment provides a graphite anode material with an in-situ grown onion carbon layer structure, and the preparation method is as follows:
[0085] Weigh 100g of ferric nitrate nonahydrate, dissolve it in 200mL of distilled water, add 400g of phenolic resin, stir evenly and then ultrasonically disperse it. Then dry it at 80℃ for 10 hours to obtain dried particles with D50=6.8um.
[0086] Weigh 100g of graphite particles with D50 = 5.2um, mix them with the dried particles obtained in the previous step, and add them to the granulator for granulation at a speed of 100r / min for 0.5 hours.
[0087] The granulated product was heated to 1000℃ at 1℃ / min under nitrogen atmosphere and held for 2 hours. Then, the temperature was further increased to 2500℃ and held for 1 hour to obtain a graphite composite anode material with an in-situ grown onion carbon layer structure.
[0088] The materials obtained in each embodiment and comparative example were mixed with commercially available graphite A in a certain proportion to form a lithium-ion battery negative electrode material with a specific capacity of 350 mAh / g. The mixture was then mixed with 2% carbon black, 2% sodium carboxymethyl cellulose, and 3% styrene-butadiene rubber by mass ratio in polyvinylidene fluoride (PVDF) solvent to form a battery slurry. The slurry was coated onto copper foil, dried, and cut into 14 mm diameter discs. After vacuum drying at 100 °C for 12 hours, the lithium foil was assembled into button cells in a glove box. The structure and electrochemical performance were evaluated by testing, and the results are recorded in Table 1.
[0089]
[0090] Table 1
[0091] Comparing the results of the comparative and example examples shows that in-situ growth of an onion-like carbon layer on graphite anode material can significantly improve the first-cycle efficiency. Figure 3 As can be seen from the TEM image, the outermost amorphous structure of graphite is transformed into an onion-like carbon layer structure, which reduces the formation of the SEI film and the adsorption of surface impurities, reduces irreversible capacity, and improves the first cycle efficiency.
[0092] A lithium-ion battery was also prepared using commercial graphite A as the negative electrode according to the above method. Its cycle performance was compared with that of lithium-ion batteries prepared using the graphite negative electrode materials of Example 1 and Comparative Example 1. The test was conducted at 25°C and a voltage range of 1.5–4.2V for 500 cycles. The capacity retention was as follows: Figure 4 As shown, the graphite anode material of Example 1 of this invention can still achieve a cycle capacity retention of over 92.5% after 500 cycles, which is far better than Comparative Example 1 and the case using a graphite anode.
[0093] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A graphite negative electrode material having an in-situ grown onion carbon layer structure, characterized by, The graphite anode material has a graphite core and an in-situ grown onion carbon layer as its outer shell, with a thickness of 1 nm to 1000 nm. The preparation method of the graphite anode material includes: mixing a solution containing one or more elements of iron, cobalt, and nickel with a high-carbon-residue polymer, stirring until uniform, dispersing, and drying to obtain dried particles; mixing the dried particles with graphite and granulating them using a shaping machine; heating the granulated product to 1000°C to 1300°C at a rate of 1°C / min to 10°C / min under a protective atmosphere, holding for 2 to 15 hours, and then further heating to 2000°C to 2500°C and holding for 1 to 5 hours to obtain the graphite anode material; the high-carbon-residue polymer includes one or more combinations of asphalt, phenolic resin, or epoxy resin; the solution containing one or more elements of iron, cobalt, and nickel includes one or more of ferric nitrate solution, cobalt nitrate solution, and nickel nitrate solution. The particle size range of the graphite anode material is 500 nm to 100 μm.
2. The method for preparing the graphite negative electrode material with the in-situ grown onion carbon layer structure according to claim 1, characterized in that, The preparation method includes: A solution containing a compound of one or more elements selected from iron, cobalt, and nickel is mixed with a high carbon residue polymer, stirred evenly, dispersed, and dried to obtain dried granules; the high carbon residue polymer includes one or more combinations of asphalt, phenolic resin, or epoxy resin; the solution containing a compound of one or more elements selected from iron, cobalt, and nickel includes one or more of ferric nitrate solution, cobalt nitrate solution, and nickel nitrate solution. The dried granules are mixed with graphite and granulated in a shaping machine; the mass ratio of the compound, the high carbon residue polymer and the graphite is 1:0.5:1 to 1:5:
100. The granulated product is heated to 1000℃~1300℃ at a rate of 1℃ / min~10℃ / min under a protective atmosphere and held for 2 hours~15 hours. Then, the temperature is further increased to 2000℃~2500℃ and held for 1 hour~5 hours to obtain the graphite anode material with an in-situ grown onion carbon layer structure.
3. The production method according to claim 2, characterized by, The rotation speed of the shaping machine is 100 r / min to 1000 r / min, and the granulation time is 0.5 hours to 6 hours.
4. The preparation method according to claim 2, characterized in that, The protective atmosphere is argon or nitrogen.
5. The preparation method according to claim 2, characterized in that, The drying process includes any one of the following: warm air drying, freeze drying, or spray drying.
6. A negative electrode characterized by comprising: The negative electrode includes the graphite negative electrode material with an in-situ grown onion carbon layer structure as described in claim 1.
7. A lithium battery, characterized by The lithium battery includes the negative electrode as described in claim 6.