A rare earth-doped hard carbon composite material and its preparation method

Abstract

The present invention relates to the technical field of lithium-ion batteries, and proposes a rare earth-doped hard carbon composite material and a preparation method thereof. The rare earth-doped hard carbon composite material has a core-shell structure, wherein the core is rare earth-doped hard carbon and the shell is composed of amorphous carbon and carbon nanotubes. The preparation method is as follows: S1, mixing a water-soluble hard carbon precursor, a rare earth compound, a dispersant, and a catalyst to obtain a solution A; adding a carbonate solution dropwise to the solution A at 25-150°C, stirring and dispersing, filtering, washing, and drying to obtain a rare earth-doped hard carbon precursor; S2, under nitrogen protection, passing naphthalene vapor into the rare earth-doped hard carbon precursor, reacting at 80-150°C for 1-6 hours to obtain a rare earth-doped hard carbon core; S3, carbonizing the rare earth-doped hard carbon core at 700-1100°C for 1-6 hours under the action of a carbon source gas to obtain a rare earth-doped hard carbon composite material. Through the above technical solution, the problems of low initial efficiency and power performance deviation of hard carbon materials in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a rare earth-doped hard carbon composite material and a preparation method thereof. Background Art

[0002] Hard carbon is a non-graphitizable carbon material used in 48V / HEV applications due to its fast charging and excellent low-temperature performance. However, its low inherent energy density (300 mAh / g, 1.0 g / cm³, 80%) limits its application in electric vehicles (EVs). Methods to improve the energy density of hard carbon materials include doping and coating. Doping materials offer high energy density and power performance, while also creating pores in the material, enhancing its lithium storage capacity and boosting energy density. For example, patent application CN 114678505 A discloses a sulfur-phosphorus co-doped hard carbon composite. Phosphorus atoms are doped into the hard carbon core. The pores formed during the preparation process utilize the catalytic action of the sulfur-phosphorus compound to enhance the material's lithium storage activity and the high specific capacity of phosphorus itself, thereby increasing energy density. Sulfur atoms are doped into the carbon interlayers, increasing the interlayer spacing and surface active sites, boosting lithium ion migration and improving power performance. However, the initial efficiency of this sulfur-phosphorus co-doped hard carbon material remains low, and its power performance is poor. Summary of the Invention

[0003] The present invention provides a rare earth doped hard carbon composite material and a preparation method thereof, which solves the problems of low initial efficiency and power performance deviation of hard carbon materials in the prior art.

[0004] The technical solutions of the present invention are as follows:

[0005] The present invention provides a rare earth doped hard carbon composite material. The rare earth doped hard carbon composite material has a core-shell structure, wherein the core is rare earth doped hard carbon and the shell is composed of amorphous carbon and carbon nanotubes.

[0006] As a further technical solution, the mass of the shell is 1-10% of the mass of the rare earth-doped hard carbon composite material.

[0007] The present invention also provides a method for preparing a rare earth-doped hard carbon composite material, comprising the following steps:

[0008] S1. Mix a water-soluble hard carbon precursor, a rare earth compound, a dispersant, and a catalyst to obtain a solution A; add the carbonate solution dropwise to the solution A at 25-150° C., stir and disperse, filter, wash, and dry to obtain a rare earth-doped hard carbon precursor;

[0009] S2. Under nitrogen protection, introducing naphthalene vapor into the rare earth-doped hard carbon precursor and reacting at 80-150° C. for 1-6 hours to obtain a rare earth-doped hard carbon core;

[0010] S3. Under the action of carbon source gas, carbonize the rare earth-doped hard carbon core at 700-1100° C. for 1-6 hours to obtain a rare earth-doped hard carbon composite material.

[0011] As a further technical solution, in S1,

[0012] The water-soluble hard carbon precursor is one of water-soluble phenolic resin, water-soluble furfural resin and water-soluble epoxy resin;

[0013] The rare earth compound is a chloride or nitrate of a rare earth metal; the rare earth metal is one or more of zirconium, lanthanum, cerium, praseodymium, neodymium, samarium, dysprosium, and holmium;

[0014] The dispersant is one or more of sodium lignin sulfonate, sodium carboxymethyl cellulose, sodium lauryl sulfate, and hexadecyltrimethylammonium bromide;

[0015] The catalyst is one of the chlorides of iron, cobalt, and nickel or the nitrates of iron, cobalt, and nickel.

[0016] As a further technical solution, in S1, by mass, water-soluble hard carbon precursor: rare earth compound: dispersant: catalyst: base = 100: (1-10): (0.5-2): (0.5-2): (1-10).

[0017] As a further technical solution, in S1, the stirring and dispersing time is 1-6 hours.

[0018] As a further technical solution, in S1, the mass concentration of the carbonate solution is 1-10%, and the carbonate is one of sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

[0019] As a further technical solution, in S2, the mass ratio of naphthalene to the rare earth-doped hard carbon precursor is 10-50:100.

[0020] As a further technical solution, in S2, the carbon source gas is one of methane, acetylene, and ethylene.

[0021] The present invention also provides a lithium-ion battery electrode, comprising the rare earth-doped hard carbon composite material, or the rare earth-doped hard carbon composite material prepared by the preparation method.

[0022] The present invention also provides a lithium ion battery comprising the lithium ion battery electrode.

[0023] The working principle and beneficial effects of the present invention are:

[0024] 1. In the present invention, the hard carbon composite material has a core-shell structure, in which the core is doped with rare earth metals. The addition of rare earth metals, on the one hand, expands the interlayer spacing of graphite and increases the lithium ion deintercalation rate, thereby improving the rate performance of the material. On the other hand, the rare earth metals are filled in the pores of the hard carbon, which increases the material's tap density and electronic conductivity, thereby improving the material's initial efficiency and cycle performance, solving the problems of low initial efficiency and power performance deviation of hard carbon materials in the prior art.

[0025] 2. In the present invention, in the preparation of the hard carbon composite material, a rare earth-doped hard carbon precursor is first prepared, and then naphthalene is deposited on the outer layer of the rare earth-doped hard carbon precursor to release the stress between the materials and reduce the defects of the materials, thereby obtaining a rare earth-doped hard carbon core, and then the outer layer is coated with amorphous carbon / carbon nanotubes, thereby further improving the initial efficiency of the hard carbon composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 This is an SEM image of the rare earth-doped hard carbon composite material of Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing a rare earth-doped hard carbon composite material comprises the following steps:

[0031] S1. Preparation of rare earth doped hard carbon precursor

[0032] 100 g of water-soluble phenolic resin, 5 g of lanthanum chloride, 1 g of sodium lignin sulfonate, and 1 g of ferric chloride were uniformly dispersed to obtain solution A;

[0033] Prepare 100 mL of 5% sodium carbonate aqueous solution to obtain solution B;

[0034] At 80°C, solution B was slowly added dropwise to solution A, and the mixture was dispersed under stirring for 3 hours. The mixture was then filtered, washed with dilute hydrochloric acid, and vacuum-dried at 80°C for 24 hours to obtain a rare earth-doped hard carbon precursor.

[0035] S2. Preparation of rare earth doped hard carbon core

[0036] 30 g of naphthalene was heated to 220° C. at a heating rate of 5° C. / min in a closed reactor A under nitrogen to obtain naphthalene vapor;

[0037] 100 g of rare earth-doped hard carbon precursor was placed in a closed reactor B with nitrogen and heated to 120 °C at a heating rate of 5 °C / min;

[0038] Reactor A and reactor B were connected by a conduit, and naphthalene vapor was passed into the rare earth-doped hard carbon precursor for full absorption. The reaction time was 3 h to obtain a rare earth-doped hard carbon core.

[0039] S3. Preparation of amorphous carbon / carbon nanotube-coated rare earth-doped hard carbon composites

[0040] The rare earth-doped hard carbon core was transferred to a tubular furnace. Argon inert gas was first introduced to expel the air in the tubular furnace, and then methane gas was introduced. The core was carbonized at 900°C for 3 hours, naturally cooled to room temperature, and crushed to obtain a rare earth-doped hard carbon composite material.

[0041] Example 2

[0042] A method for preparing a rare earth-doped hard carbon composite material comprises the following steps:

[0043] S1. Preparation of rare earth doped hard carbon precursor

[0044] 100 g of water-soluble epoxy resin, 1 g of cerium chloride, 0.5 g of sodium lauryl sulfate, and 0.5 g of cobalt chloride were uniformly dispersed to obtain solution A;

[0045] Prepare 100 mL of 5% ammonium carbonate aqueous solution to obtain solution B;

[0046] At 25°C, solution B was slowly added dropwise to solution A, and the mixture was dispersed under stirring for 3 hours. The mixture was then filtered, washed with dilute hydrochloric acid, and vacuum-dried at 80°C for 24 hours to obtain a rare earth-doped hard carbon precursor.

[0047] S2. Preparation of rare earth doped hard carbon core

[0048] 10 g of naphthalene was heated to 200° C. at a heating rate of 1° C. / min in a closed reactor A under nitrogen to obtain naphthalene vapor;

[0049] 100 g of rare earth-doped hard carbon precursor was placed in a closed reactor B with nitrogen and heated to 80 °C at a heating rate of 1 °C / min;

[0050] Reactor A and reactor B were connected by a conduit, and naphthalene vapor was passed into the rare earth-doped hard carbon precursor for full absorption. The reaction time was 1 hour to obtain a rare earth-doped hard carbon core.

[0051] S3. Preparation of amorphous carbon / carbon nanotube-coated rare earth-doped hard carbon composites

[0052] The rare earth-doped hard carbon core was transferred to a tubular furnace. Argon inert gas was first introduced to expel the air in the tubular furnace, and then acetylene gas was introduced. The core was carbonized at 700°C for 6 hours, naturally cooled to room temperature, and crushed to obtain a rare earth-doped hard carbon composite material.

[0053] Example 3

[0054] A method for preparing a rare earth-doped hard carbon composite material comprises the following steps:

[0055] S1. Preparation of rare earth doped hard carbon precursor

[0056] 100 g of water-soluble furfural resin, 10 g of neodymium chloride, 2 g of dispersant, and 2 g of nickel chloride were uniformly dispersed to obtain solution A;

[0057] Prepare 100 mL of 5% ammonium bicarbonate aqueous solution to obtain solution B;

[0058] At 150°C, solution B was slowly added dropwise to solution A, and the mixture was dispersed under stirring for 1 hour. The mixture was then filtered, washed with dilute hydrochloric acid, and vacuum-dried at 80°C for 24 hours to obtain a rare earth-doped hard carbon precursor.

[0059] S2. Preparation of rare earth doped hard carbon core

[0060] 50 g of naphthalene was heated to 250° C. at a heating rate of 10° C. / min in a closed reactor A under nitrogen to obtain naphthalene vapor;

[0061] 100 g of rare earth-doped hard carbon precursor was placed in a closed reactor B with nitrogen and heated to 150 °C at a heating rate of 10 °C / min;

[0062] Reactor A and reactor B were connected by a conduit, and naphthalene vapor was passed into the rare earth-doped hard carbon precursor for full absorption. The reaction time was 6 h to obtain a rare earth-doped hard carbon core.

[0063] S3. Preparation of amorphous carbon / carbon nanotube-coated rare earth-doped hard carbon composites

[0064] The rare earth-doped hard carbon core was transferred to a tubular furnace. Argon inert gas was first introduced to expel the air in the tubular furnace, and then methane gas was introduced. The core was carbonized at 1100°C for 1 hour, naturally cooled to room temperature, and crushed to obtain a rare earth-doped hard carbon composite material.

[0065] Comparative Example 1

[0066] A method for preparing a hard carbon composite material comprises the following steps:

[0067] S1. Preparation of hard carbon precursor

[0068] 100 g of water-soluble phenolic resin was mixed evenly with 100 mL of 5% ammonium bicarbonate aqueous solution, stirred and dispersed at 80° C. for 3 h, then filtered, washed with dilute hydrochloric acid, and vacuum-dried at 80° C. for 24 h to obtain a hard carbon precursor;

[0069] S2. Preparation of hard carbon core

[0070] 30 g of naphthalene was heated to 220° C. at a heating rate of 5° C. / min in a closed reactor A under nitrogen to obtain naphthalene vapor;

[0071] 100 g of hard carbon precursor was placed in a closed reactor B with nitrogen and heated to 120 °C at a heating rate of 5 °C / min;

[0072] Reactor A and reactor B were connected by a tube, and naphthalene vapor was passed into the rare earth-doped hard carbon precursor for full absorption. The reaction was continued for 3 hours to obtain a hard carbon core.

[0073] S3. Preparation of amorphous carbon / carbon nanotube-coated hard carbon composites

[0074] The hard carbon core was transferred to a tubular furnace, and argon inert gas was first introduced to expel the air in the tubular furnace, and then methane gas was introduced. It was carbonized at 900°C for 3 hours, naturally cooled to room temperature, and crushed to obtain a hard carbon composite material.

[0075] Comparative Example 2

[0076] A method for preparing a rare earth-doped hard carbon composite material comprises the following steps:

[0077] S1. Preparation of rare earth doped hard carbon precursor

[0078] 100 g of water-soluble phenolic resin, 5 g of lanthanum chloride, 1 g of sodium lignin sulfonate, and 1 g of ferric chloride were uniformly dispersed to obtain solution A;

[0079] Prepare 100 mL of 5% sodium carbonate aqueous solution to obtain solution B;

[0080] At 80°C, solution B was slowly added dropwise to solution A, and the mixture was dispersed under stirring for 3 hours. The mixture was then filtered, washed with dilute hydrochloric acid, and vacuum-dried at 80°C for 24 hours to obtain a rare earth-doped hard carbon precursor.

[0081] S2. Preparation of amorphous carbon / carbon nanotube-coated rare earth-doped hard carbon composites

[0082] The rare earth-doped hard carbon precursor was transferred to a tubular furnace. Argon inert gas was first introduced to expel the air in the tubular furnace, and then methane gas was introduced. It was carbonized at 900°C for 3 hours, naturally cooled to room temperature, and crushed to obtain a rare earth-doped hard carbon composite material.

[0083] Experimental Example 1 SEM test

[0084] The rare earth doped hard carbon composite material prepared in Example 1 was subjected to SEM testing, and the results were as follows: Figure 1 As shown, the hard carbon negative electrode material prepared in Example 1 has a granular structure with a small amount of micropores on the surface, uniform size distribution, and a particle size of 5-15 μm.

[0085] Experimental Example 2: Physical and Chemical Properties and Button Battery Test

[0086] The hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were assembled into button-type batteries A1, A2, A3, B1, and B2. The preparation method was as follows: a binder, a conductive agent, and a solvent were added to the negative electrode material, stirred to make a slurry, coated on a copper foil, and dried and rolled to obtain the result.

[0087] The binder used was LA132, the conductive agent was SP, the negative electrode materials were the hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2, and the solvent was double-distilled water. The ratios were: negative electrode material: SP: LA132: double-distilled water = 95 g: 1 g: 4 g: 220 mL, and a negative electrode sheet was prepared.

[0088] The electrolyte was LiPF6 / EC+DEC (volume ratio 1:1, concentration 1.3 mol / L), the metal lithium sheet was the counter electrode, and the separator was a polyethylene PE, polypropylene PP, or polyethylene propylene PEP composite film. The simulated battery assembly was carried out in an argon-filled glove box, and the electrochemical performance was measured on a Wuhan Blue Electric CT2001A battery tester with a charge and discharge voltage range of 0.00 V to 2.0 V and a charge and discharge rate of 0.1C.

[0089] Test the rate (2C / 0.1C) and cycle performance (0.2C / 0.2C, 200 times) of its button battery.

[0090] The test results are shown in the following table:

[0091] Table 1 Physical and chemical properties and button battery test results

[0092] serial number project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 1 Particle size (D50, μm) 7.6 7.9 7.5 9.1 8.9 2 <![CDATA[Tap density (g / cm 3 )]]> 0.89 0.85 0.82 0.72 0.74 3 <![CDATA[Specific surface area (m 2 / g)]]> 7.9 7.5 7.7 4.9 3.8 4 Interlayer spacing (nm) 0.389 0.387 0.381 0.368 0.378 5 Trace elements (rare earth) 4.8％ 1.02％ 9.94％ 0％ 4.7％ 6 First discharge capacity (mAh / g) 459 446 438 345 434.3 7 First efficiency (%) 86.2 86.4 85.6 82.3 83.9 8 Rate performance (2C / 0.1C) 92.5 91.6 90.1 84.3 86.3 9 Cycle performance (capacity retention) 94.7 93.3 92.9 89.3 90.3

[0093] As can be seen from Table 1, compared with Comparative Examples 1-2, the first discharge capacity and first efficiency, rate performance and cycle performance of the hard carbon negative electrode materials prepared in Examples 1-3 are significantly improved. The reason is that in the rare earth-doped hard carbon composite materials of Examples 1-3, the doped rare earth metal expands the interlayer spacing of graphite, increases the lithium ion deintercalation rate, and thus improves the rate performance of the material. At the same time, the rare earth metal is filled in the hard carbon pores to increase the tap density and electronic conductivity of the material, thereby improving the first efficiency and cycle performance of the material. Naphthalene vapor is deposited on the outer layer of the rare earth-doped hard carbon precursor to release the stress between the materials, reduce the defects of the materials, and further improve the first efficiency of the material.

[0094] Experimental Example 3 Soft Pack Battery

[0095] The hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were used as negative electrode materials to prepare negative electrode sheets. 1 / 3 Co 1 / 3 Mn 1 / 3 5Ah soft-pack batteries C1, C2, C3 and D1, D2 were prepared using LiPF6 (solvent: EC+DEC, volume ratio: 1:1, concentration: 1.3 mol / L) as electrolyte and celegard2400 as separator, i.e., ternary lithium batteries were obtained. The rate performance of the soft-pack batteries was tested in the charge and discharge voltage range of 2.5-4.2V, temperature of 25±3.0℃, charging at 1.0C, 3.0C, 5.0C, 10.0C, and 20.C, and discharging at 1.0C. The results are shown in Table 2:

[0096] Table 2 Rate performance test results of soft pack batteries

[0097]

[0098]

[0099] It can be seen from the above table that the rate charging performance of the soft-pack batteries in Examples 1-3 is significantly better than that in Comparative Examples 1 and 2, that is, the charging time of the soft-pack batteries in Examples 1-3 is shorter. The reason is that in the rare earth-doped hard carbon composite materials of Examples 1-3, the doped rare earth metal expands the interlayer spacing of graphite and increases the lithium ion deintercalation rate, thereby improving the rate performance of the soft-pack batteries.

[0100] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rare earth-doped hard carbon composite material, characterized in that: The rare earth-doped hard carbon composite material has a core-shell structure, wherein the core is rare earth-doped hard carbon and the shell is composed of amorphous carbon and carbon nanotubes. The preparation method of the rare earth-doped hard carbon composite material comprises the following steps: S1. Mix a water-soluble hard carbon precursor, a rare earth compound, a dispersant, and a catalyst to obtain a solution A; add the carbonate solution dropwise to the solution A at 25-150° C., stir and disperse, filter, wash, and dry to obtain a rare earth-doped hard carbon precursor; S2. Under nitrogen protection, introducing naphthalene vapor into the rare earth-doped hard carbon precursor and reacting at 80-150° C. for 1-6 hours to obtain a rare earth-doped hard carbon core; S3. Under the action of carbon source gas, carbonize the rare earth-doped hard carbon core at 700-1100° C. for 1-6 hours to obtain a rare earth-doped hard carbon composite material.

2. The rare earth-doped hard carbon composite material according to claim 1, characterized in that: The mass of the shell is 1-10% of the mass of the rare earth-doped hard carbon composite material.

3. The rare earth-doped hard carbon composite material according to claim 1, characterized in that: In S1, the water-soluble hard carbon precursor is one of a water-soluble phenolic resin, a water-soluble furfural resin, and a water-soluble epoxy resin; The rare earth compound is a chloride or nitrate of a rare earth metal; the rare earth metal is one or more of zirconium, lanthanum, cerium, praseodymium, neodymium, samarium, dysprosium, and holmium; The dispersant is one or more of sodium lignin sulfonate, sodium carboxymethyl cellulose, sodium lauryl sulfate, and hexadecyltrimethylammonium bromide; The catalyst is one of the chlorides of iron, cobalt, and nickel or the nitrates of iron, cobalt, and nickel.

4. The rare earth-doped hard carbon composite material according to claim 1, characterized in that: In S1, by mass, the water-soluble hard carbon precursor: the rare earth compound: the dispersant: the catalyst: the carbonate in the carbonate solution = 100: (1-10): (0.5-2): (0.5-2): (1-10).

5. The rare earth-doped hard carbon composite material according to claim 1, characterized in that: In the above-mentioned S1, the stirring and dispersing time is 1-6 hours.

6. The rare earth-doped hard carbon composite material according to claim 1, characterized in that: In the S1, the mass concentration of the carbonate solution is 1-10%, and the carbonate is one of sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

7. The rare earth-doped hard carbon composite material according to claim 1, characterized in that: In the S2, the mass ratio of naphthalene to the rare earth-doped hard carbon precursor is 10-50:

100.

8. A lithium-ion battery electrode, characterized in that: The rare earth-doped hard carbon composite material comprises the rare earth-doped hard carbon composite material according to any one of claims 1 to 7.

9. A lithium-ion battery, characterized in that: Comprising the lithium-ion battery electrode according to claim 8.

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