A modified hard carbon anode material, its preparation method, and application

Abstract

The present invention discloses a modified hard carbon negative electrode material, a preparation method thereof, and an application. The method includes the following steps: S1 Mixing a carbonaceous material with a crosslinking agent and reacting to obtain a crosslinked carbonaceous material, and subjecting the crosslinked carbonaceous material to carbonization treatment; S2 Microwave-assisted mixing and carbonization treatment of the material obtained in S1 to obtain a modified hard carbon negative electrode material; wherein the modifier is a silver salt and a lithium salt, and the mass ratio of the silver salt to the lithium salt is 1:1 - 1:0.3. The preparation method of the present invention is simple and has low cost; the doped elements in the obtained modified hard carbon negative electrode material have good distribution uniformity and a stable structure, which is beneficial to improving its ability to quickly intercalate lithium, so that the battery has excellent electrochemical performance, such as excellent initial Coulomb efficiency, rate performance, cycle performance, reversible capacity at high rate and capacity retention rate.

Description

Technical Field

[0001] The present invention relates to a modified hard carbon negative electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] The demand for fast charging in the fields of consumer electronics and electric vehicles is increasing day by day. Graphite, as a widely used negative electrode material for lithium-ion batteries, its disadvantage in the rapid insertion and extraction of lithium ions has gradually emerged. The fast charging scenario is also a test for the structural stability of the negative electrode material.

[0003] Hard carbon has a rich pore structure and has received wide attention. During the process of rapid ion insertion and extraction, its structure can remain stable and there is no particle swelling phenomenon. Some have used the hard carbon blending technology to solve the bottleneck problems such as lithium deposition and poor kinetics during the fast charging of graphite. Moreover, compared with the theoretical capacity of graphite of 372 mAh / g, the lithium storage capacity of hard carbon is higher, and the capacity of the negative electrode end can also be improved after adding hard carbon.

[0004] However, the conductivity of hard carbon itself is lower than that of graphite, and there is still great room for improvement in its rate performance. Commonly used methods to improve the rate performance of hard carbon, such as patent EP3360182B1, reduce the particle size scale and shorten the transmission distance between particles, but it may bring more electrolyte consumption and the defect of reduced initial efficiency. Metal doping can also improve the conductivity, but it has higher requirements for the process control process. How to obtain a hard carbon negative electrode material with a simple preparation method, excellent initial Coulomb efficiency and rate performance is an urgent problem to be solved in this field. Summary of the Invention

[0005] The technical problem solved by the present invention is to overcome the defects in the prior art that the preparation process of hard carbon negative electrode materials is relatively complex and it is impossible to have both excellent initial Coulomb efficiency and rate performance, and to provide a modified hard carbon negative electrode material, a preparation method thereof, and an application thereof.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The present invention provides a preparation method of a modified hard carbon negative electrode material, which includes the following steps:

[0008] S1 Mix a carbonaceous material with a crosslinking agent and react to obtain a crosslinked carbonaceous material, and carbonize the crosslinked carbonaceous material;

[0009] S2 Microwave-assisted mixing and sintering of the material obtained in S1 and a modifier to obtain the modified hard carbon negative electrode material;

[0010] Wherein, the modifier is a silver salt and a lithium salt, and the mass ratio of the silver salt to the lithium salt is 1:1 - 1:0.3.

[0011] In S1, the carbonaceous material can be conventional in the art, such as one or more of phenolic resin, epoxy resin, furfural resin, peanut shell, crayfish shell, anthracite, pitch, corncob, rice husk, glucose, and tapioca flour, such as phenolic resin and / or glucose.

[0012] In a preferred embodiment, the carbonaceous material is phenolic resin and glucose, and the mass ratio of phenolic resin to glucose is (0.2 - 4):1, such as 1:4, 2:3, 3:2, or 4:1.

[0013] In S1, the mass ratio of the carbonaceous material to the crosslinking agent is preferably 100:(5 - 30), such as 100:15.

[0014] In S1, the crosslinking agent can be a conventional substance in the art that can crosslink the carbonaceous material, such as maleic acid and / or methanol.

[0015] When the crosslinking agent is a mixture of maleic acid and methanol, the molar ratio of maleic acid to methanol is preferably 1:0.8 - 1.2, such as 1:1.

[0016] In S1, the crosslinking agent is generally added in the form of a solution.

[0017] When the crosslinking agent is used in the form of a solution, the solvent in the solution is generally water.

[0018] When the crosslinking agent is used in the form of a solution, the concentration of the crosslinking agent can be conventional in the art, such as 3 mol / L.

[0019] In S1, the temperature of the mixing reaction is preferably 50 - 180 °C, such as 120 °C.

[0020] In S1, the time of the mixing reaction is preferably 2 - 12 h.

[0021] In S1, the mixing reaction can be carried out under atmospheric pressure.

[0022] After the mixing reaction in S1, it is generally cooled naturally.

[0023] After the mixing reaction in S1, it is preferably to crush and classify the crosslinked carbonaceous material.

[0024] Among them, the particle size of the product after crushing and classification is preferably 5 - 10 μm.

[0025] In S1, the temperature of the carbonization treatment is preferably 500 - 575 °C.

[0026] In S1, the time of the carbonization treatment is preferably 2 - 4 h, such as 3 h.

[0027] In S1, the pressure of the carbonization treatment is preferably 1 MPa - 1.3 MPa.

[0028] In S1, the atmosphere of the carbonization treatment is generally an inert atmosphere or a nitrogen atmosphere. The inert atmosphere can be an argon atmosphere.

[0029] In S1, the rate of heating to the carbonization treatment temperature is preferably 2 - 3 °C / min, such as 2.3 °C / min.

[0030] In S1, after the carbonization treatment, it is generally cooled naturally.

[0031] In S1, after the operation of the carbonization treatment, comminution and screening are preferably carried out. The particle size of the material after comminution and screening is preferably 3 - 5 μm, such as 3 μm, 4 μm or 5 μm.

[0032] In S2, the mass ratio of the modifier to the carbonaceous material is preferably 0.01 - 0.1:100, such as 0.05:100.

[0033] In S2, the silver salt is preferably one or more of silver nitrate, silver acetate, silver chloride, silver carbonate and silver phosphate, such as silver acetate.

[0034] In S2, the lithium salt is preferably one or more of lithium nitrate, lithium acetate, lithium chloride and lithium carbonate, such as lithium acetate.

[0035] In S2, the mass ratio of the silver salt to the lithium salt is preferably 1:1 - 1:0.3, such as 1:0.3, 1:0.5, 1:0.8 or 1:1.

[0036] In S2, the frequency of the microwave-assisted mixing is preferably 1400 - 1600 MHz, such as 1500 MHz.

[0037] In S2, the time of the microwave-assisted mixing is preferably 10 - 14 h, such as 12 h.

[0038] In S2, the pressure of the sintering can be 101 Kpa - 100 Pa, such as 101 KPa.

[0039] In S2, the temperature of the sintering can be 1000 - 1200 °C, such as 1120 °C.

[0040] In S2, the time of the sintering can be 2 - 3 h, such as 3 h.

[0041] In S2, the rate of heating to the sintering temperature is preferably 2 - 3 °C / min, such as 3 °C / min.

[0042] The present invention also provides a modified hard carbon negative electrode material prepared by the above preparation method.

[0043] The present invention also provides an application of the modified hard carbon negative electrode material in a lithium-ion battery.

[0044] On the basis of conforming to the common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0045] The reagents and raw materials used in the present invention are all commercially available.

[0046] The positive progressive effects of the present invention are as follows:

[0047] The preparation method of the present invention is simple and has low cost; the doped elements in the obtained modified hard carbon negative electrode material have good distribution uniformity and a stable structure, which is beneficial to improving its ability to quickly intercalate lithium, so that the battery has excellent electrochemical performance, such as excellent initial Coulomb efficiency, rate performance, cycle performance, reversible capacity and capacity retention rate at high rates. Description of the Drawings

[0048] Figure 1 It is a scanning electron microscope image of the modified hard carbon negative electrode material prepared in Example 1. Detailed Embodiments

[0049] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0050] Example 1

[0051] S1 Weigh 3000 g of phenolic resin and 2000 g of glucose and dissolve them together in an aqueous solution of 3.0 mol / L maleic acid and 3 mol / L methanol (in the mixed solution, the molar ratio of maleic acid to methanol is 1:1). Under normal pressure, heat to 120 °C and carry out a cross-linking reaction for 12 h. After the reaction is completed, naturally cool to room temperature; among them, the mass ratio of the carbonaceous materials (phenolic resin and glucose) to the cross-linking agent (maleic acid and methanol) is 100:15;

[0052] The obtained product is put into air-flow crushing. The particle size of the obtained carbonaceous raw material is 5 - 10 μm. Under a nitrogen atmosphere of 1.0 MPa, heat it to 500 °C at a rate of 2.3 °C / min and keep it for 3 h, then naturally cool to room temperature. The particle size of the crushed and sieved material is 5 μm;

[0053] 5200 g of the carbonaceous material after S2 pretreatment is mixed with an aqueous solution of the modifier (the modifier is silver acetate and lithium acetate, the amount of water is 200 mL, the mass ratio of silver acetate to lithium acetate is 1:1, and the modifier is 2.5 g) by microwave assistance. The microwave frequency is 1500 MHz, and the microwave treatment time is 12 h. The uniformly mixed material is heated to 1120 °C at a rate of 3 °C / min and sintered at a pressure of 101 KPa for 3 h to obtain a modified hard carbon anode material.

[0054] Example 2

[0055] Compared with Example 1, Example 2 is only different in that the mass ratio of silver acetate to lithium acetate is 1:0.8, and other operations and conditions are the same as those in Example 1.

[0056] Example 3

[0057] Compared with Example 1, Example 3 is only different in that the mass ratio of silver acetate to lithium acetate is 1:0.5, and other operations and conditions are the same as those in Example 1.

[0058] Example 4

[0059] Compared with Example 1, Example 4 is only different in that the mass ratio of silver acetate to lithium acetate is 1:0.3, and other operations and conditions are the same as those in Example 1.

[0060] Example 5

[0061] Compared with Example 2, Example 5 is only different in that the raw materials are changed to 2000 of phenolic resin and 3000 g of glucose, and other operations and conditions are the same as those in Example 2.

[0062] Example 6

[0063] Compared with Example 2, Example 6 is only different in that the raw materials are changed to 1000 of phenolic resin and 4000 g of glucose, and other operations and conditions are the same as those in Example 2.

[0064] Example 7

[0065] Compared with Example 2, Example 7 is only different in that the raw materials are changed to 4000 of phenolic resin and 1000 g of glucose, and other operations and conditions are the same as those in Example 2.

[0066] Example 8

[0067] Compared with Example 2, Example 8 is only different in that after the carbonaceous material is cross-linked in step S1 and then carbonized, the crushing particle size is 3 μm, and other operations and conditions are the same as those in Example 2.

[0068] Example 9

[0069] Example 9 is different from Example 2 only in that after the cross-linked carbonaceous material is carbonized in step S1, the crushed particle size is 4 μm, and other operations and conditions are the same as those in Example 2.

[0070] Comparative Example 1

[0071] Comparative Example 1 is different from Example 1 in that there is no step of modifying with silver acetate and lithium acetate, and other operations and conditions are the same as those in Example 1.

[0072] Comparative Example 2

[0073] Comparative Example 2 is different from Example 1 only in that the mass ratio of silver acetate to lithium acetate is 1:0 (i.e., only modified with silver acetate), and other operations and conditions are the same as those in Example 1.

[0074] Comparative Example 3

[0075] Comparative Example 3 is different from Comparative Example 2 only in that there is no microwave-assisted mixing, and other operations and conditions are the same as those in Example 1.

[0076] Comparative Example 4

[0077] Comparative Example 4 is different from Example 1 only in that the mass ratio of silver acetate to lithium acetate is 0:1 (i.e., only modified with lithium acetate), and other operations and conditions are the same as those in Example 1.

[0078] Effect Example 1 Physical property test of the modified hard carbon negative electrode material

[0079] The modified hard carbon negative electrode materials obtained in Examples 1-4 and Comparative Examples 1-4 were measured for particle size D50, tapped density, and specific surface area (BET). The instruments and models used for the above index tests are shown in Table 1, and the specific data are shown in Table 2.

[0080] Table 1

[0081] Test Index Instruments and Models Used Particle Size D50 Laser Particle Size Analyzer MS3000 Tap Density Tap Density Tester BT-302 Specific Surface Area (BET) Specific Surface Area Analyzer NOVATouch2000

[0082] Figure 1 Figure 40 is a scanning electron microscope image of the modified hard carbon negative electrode material prepared in Example 1.

[0083] Effect Example 2

[0084] The modified hard carbon negative electrode materials obtained in Examples 1-7 were assembled into coin cells as active materials: the ratio of active material, binder, and conductive agent was 95:3:2, and a slurry was made under a certain rate of stirring. The slurry was coated on a 5-μm-thick copper foil, then dried, rolled, and cut into a 16-mm-diameter electrode sheet. The areal density of the active material was 100 g / m 2Using a lithium sheet as the counter electrode, 1.0 M LiPF6 (EC / DMC = 1 / 1, v / v) as the electrolyte, and a PP-based thin film as the separator, a CR2032 coin cell was fabricated.

[0085] The first efficiency test of the above half-cell was carried out on an Arbin BT2000 battery tester in the United States. The charge-discharge voltage range was 0.005 V - 2.0 V, and the charge-discharge rate was 0.1 C, where 1 C = 500 mA / g. The test results are shown in Table 2.

[0086] The rate performance of the above half-cell was tested on an Arbin BT2000 battery tester in the United States. The test conditions were as follows: the charging current was 0.1 C (1 C = 500 mA / g), and the discharging current was 0 - 5.0 C. Capacity recovery rate = R xC(x＝1,2,3,5)) / R 0.1C * 100%, where R x is the discharge capacity at xC, and R 0.1 is the first 0.1 C charging capacity, with 1 C = 500 mA / g. The test results are shown in Table 3.

[0087] Table 2 Physical and chemical parameters and first efficiency of the products in Examples 1 - 9 and Comparative Examples 1 - 4

[0088]

[0089] Regarding the first efficiency, among Examples 1 - 4 of the present invention, in Example 2, the Ag:Li mass ratio is 1:0.8, and the first efficiency is the best, followed by Example 1, Example 4, and Example 3. From the comparison of Examples 6, 5, 2, and 7 of the present invention, the mass ratios of phenolic resin to glucose are 0.25, 0.6, 1.5, and 4 respectively, and the rate performance first increases and then decreases. The first efficiency of Example 2 is the best. From the comparison of Examples 2, 8 - 9 of the present invention, the particle size of Example 8 is the smallest, and the first efficiency of Example 2 is the best. In Comparative Example 1, there is no Ag or Li modification, and its first efficiency is the worst. In Comparative Examples 2 - 4, there is only single Ag or Li modification, and their first efficiencies are better than those of Comparative Example 1, but still worse than those of Examples 1 - 9 of the present invention; the first efficiency of Comparative Example 4 is better than those of Comparative Examples 1 - 3.

[0090] Table 3 Rate performance and capacity recovery rate data of Examples 1 - 9 and Comparative Examples 1 - 4

[0091]

[0092] In terms of rate performance, there is no Ag or Li modification in Comparative Example 1, and its rate performance is the worst. In Comparative Examples 2-3, there is only Ag modification, and the effect of Comparative Example 2 with microwave treatment is better than that of Comparative Example 3 without microwave treatment. In Examples 1-4 of the present invention, the Ag:Li mass ratio in Example 4 is 1:0.3, and the rate performance is the best; followed by Example 3 and Examples 1-2. From the comparison of Examples 6, 5, 2, and 7 of the present invention, the mass ratios of phenolic resin to glucose are 0.25, 0.6, 1.5, and 4 respectively, and the rate performance first increases and then decreases, and the rate performance of Example 2 is the best. From the comparison of Examples 2, 8-9 of the present invention, the particle size of Example 8 is the smallest and the rate performance is the best.

[0093] In terms of capacity recovery rate, there is no Ag or Li modification in Comparative Example 1, and its capacity recovery rate is the worst. In Comparative Examples 2-4, there is only single Ag or Li modification, and its capacity recovery rate is better than that of Comparative Example 1, but still worse than that of Examples 1-4 of the present invention. The capacity recovery rates of Examples 1-9 are relatively excellent, all between 98.6-99.9%.

Claims

1. A preparation method of a modified hard carbon anode material, characterized in that It includes the following steps: S1 Mix and react a carbonaceous material with a crosslinking agent to obtain a crosslinked carbonaceous material, and subject the crosslinked carbonaceous material to carbonization treatment; S2 Microwave-assisted mixing and sintering of the material obtained in S1 and a modifier to obtain the modified hard carbon negative electrode material; wherein, the modifier is a silver salt and a lithium salt, and the mass ratio of the silver salt to the lithium salt is 1:1 - 1:0.3; the sintering temperature is 1000 - 1200 °C.

2. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S1, the carbonaceous material is one or more of phenolic resin, epoxy resin, furfural resin, peanut shell, crayfish shell, anthracite, asphalt, corn cob, rice husk, glucose, and tapioca starch; And / or, in S1, the mass ratio of the carbonaceous material to the crosslinking agent is 100:(5 - 30); And / or, in S1, the crosslinking agent is maleic acid and / or methanol.

3. The preparation method of the modified hard carbon negative electrode material according to claim 2, wherein In S1, the carbonaceous material is phenolic resin and / or glucose; And / or, in S1, the mass ratio of the carbonaceous material to the crosslinking agent is 100:15; And / or, in S1, when the crosslinking agent is a mixture of maleic acid and methanol, the molar ratio of maleic acid to methanol is 1:0.8 - 1.

2.

4. The preparation method of the modified hard carbon negative electrode material according to claim 3, characterized in that, In S1, when the carbonaceous material is phenolic resin and glucose, the mass ratio of phenolic resin to glucose is (0.2 - 4):1; And / or, in S1, when the crosslinking agent is a mixture of maleic acid and methanol, the molar ratio of maleic acid to methanol is 1:

1.

5. The preparation method of the modified hard carbon negative electrode material according to claim 4, characterized in that, In S1, when the carbonaceous material is phenolic resin and glucose, the mass ratio of phenolic resin to glucose is 1:4, 2:3, 3:2, or 4:

1.

6. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S1, the temperature of the mixing reaction is 50 - 180 °C; And / or, in S1, the time of the mixing reaction is 2 - 12 h; And / or, in S1, after the mixing reaction, the crosslinked carbonaceous material is pulverized and classified.

7. The preparation method of the modified hard carbon negative electrode material according to claim 6, wherein In S1, the temperature of the mixing reaction is 120 °C; And / or, in S1, the particle size of the product after pulverization and classification is 5 - 10 μm.

8. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S1, the temperature of the carbonization treatment is 500 - 575 °C; And / or, in S1, the time of the carbonization treatment is 2 - 4 h; And / or, in S1, the pressure of the carbonization treatment is 1 MPa - 1.3 MPa; And / or, in S1, the rate of increasing the temperature to the carbonization treatment temperature is 2 - 3 °C / min.

9. The preparation method of the modified hard carbon negative electrode material according to claim 8, characterized in that, In S1, the time of the carbonization treatment is 3 h; And / or, in S1, the rate of increasing the temperature to the carbonization treatment temperature is 2.3 °C / min.

10. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S1, after the carbonization treatment operation, pulverization and screening are carried out.

11. The preparation method of the modified hard carbon negative electrode material according to claim 10, characterized in that, In S1, the particle size of the material after pulverization and screening is 3 - 5 μm.

12. The preparation method of the modified hard carbon negative electrode material according to claim 11, characterized in that, In S1, the particle size of the material after pulverization and screening is 3 μm, 4 μm, or 5 μm.

13. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S2, the mass ratio of the modifier to the carbonaceous material is 0.01 - 0.1:100; And / or, in S2, the silver salt is one or more of silver nitrate, silver acetate, silver chloride, silver carbonate, and silver phosphate; And / or, in S2, the lithium salt is one or more of lithium nitrate, lithium acetate, lithium chloride, and lithium carbonate.

14. The preparation method of the modified hard carbon negative electrode material according to claim 13, characterized in that, In S2, the mass ratio of the modifier to the carbonaceous material is 0.05:100; And / or, in S2, the silver salt is silver acetate; And / or, in S2, the lithium salt is lithium acetate.

15. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S2, the mass ratio of the silver salt to the lithium salt is 1:1 - 1:0.

3.

16. The preparation method of the modified hard carbon negative electrode material according to claim 15, characterized in that, In S2, the mass ratio of the silver salt to the lithium salt is 1:0.3, 1:0.5, 1:0.8 or 1:

1.

17. The preparation method of the modified hard carbon negative electrode material according to claim 1, characterized in that, In S2, the frequency of the microwave-assisted mixing is 1400 - 1600 MHz; And / or, in S2, the time of the microwave-assisted mixing is 10 - 14 h; And / or, in S2, the pressure of the sintering is 101 KPa - 100 Pa; And / or, in S2, the temperature of the sintering is 1120 °C; And / or, in S2, the time of the sintering is 2 - 3 h; And / or, in S2, the rate of heating to the sintering temperature is 2 - 3 °C / min.

18. The preparation method of the modified hard carbon negative electrode material according to claim 17, characterized in that, In S2, the frequency of the microwave-assisted mixing is 1500 MHz; And / or, in S2, the time of the microwave-assisted mixing is 12 h; And / or, in S2, the time of the sintering is 3 h; And / or, in S2, the rate of heating to the sintering temperature is 3 °C / min.

19. A modified hard carbon anode material prepared by the preparation method according to any one of claims 1 - 18.

20. An application of the modified hard carbon anode material according to claim 19 in a lithium-ion battery.

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