Amorphous carbon-coated phosphorus copper-doped hard carbon composite material and its preparation method and application

Abstract

The embodiment of the present invention discloses a composite material of amorphous carbon coated with phosphorus copper doped with hard carbon, which is prepared by reacting a mixed solution of phosphoric acid and copper sulfate with a mixed solution of resin and ammonia water, then introducing formaldehyde gas for cross-linking to obtain a solid, and then spraying an organic polymer solution on the surface thereof, and carbonizing to obtain a composite material of amorphous carbon coated with phosphorus copper doped with hard carbon. The core of the composite material of the present invention is phosphorus copper doped with hard carbon, and the outer layer is coated with amorphous carbon. Copper sulfate and ammonia water are used as reactants, and copper hydroxide is generated by chemical deposition reaction and deposited on the surface of the resin or the internal pores. After carbonization, copper doping is achieved to improve the electronic conductivity of the material; the high specific capacity of phosphorus and the pore-forming effect of phosphorus improve the specific capacity of the material, and the surface of the material is cross-linked with a gas cross-linking agent formaldehyde to form pores, which has the advantages of high efficiency and good uniformity compared with liquid phase cross-linking. The polymer is deposited on the hard carbon composite material by spraying, which also has the advantages of good uniformity, thin thickness, and high preparation efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of lithium ion battery material preparation, in particular to an amorphous carbon-coated phosphorus copper-doped hard carbon composite material and a preparation method thereof. Background Art

[0002] As the market's requirements for lithium-ion battery performance increase, the negative electrode materials used in lithium-ion batteries are required to have excellent low-temperature and fast-charging performance to meet market demand. Currently, the negative electrode materials for lithium-ion batteries on the market are mainly graphite (natural graphite, artificial graphite), which has the advantages of good conductivity and high reversible specific capacity. However, the theoretical specific capacity of graphite material is only 372mAh / g, and its low-temperature performance deviation can only meet the charging capacity of ≤4C, which cannot meet the future demand for high energy density, fast charging and low temperature. Hard carbon material, as a difficult-to-graphitize material, has the advantages of isotropic structure, large interlayer spacing, small stress change, high lithium insertion capacity, and high voltage platform, which makes it have excellent low-temperature performance and rate performance, but its specific capacity is low and its initial efficiency is low, which affects its energy density.

[0003] Regarding the above-mentioned problem, although the discharge specific capacity of the material can be improved by means of material doping, coating, etc., the initial efficiency of the material is still relatively low (about 80%), thereby reducing the specific capacity of the positive electrode material and failing to improve the energy density of the entire battery. At the same time, doping will cause expansion and poor cycle performance. For example, although the silver-doped hard carbon composite material disclosed in the prior art can improve power performance, it has little effect on improving specific capacity and is relatively expensive. A sulfur-phosphorus co-doped hard carbon composite material disclosed in the prior art is prepared by adding hydrocarbons, sulfur-phosphorus organic matter, and nitrogen-containing polymers to an organic solvent to form an organic solution, and then preparing a porous hard carbon precursor through a hydrothermal reaction, and carbonizing to obtain a hard carbon composite material. Its preparation process is complicated, and the sulfur-phosphorus doping has a low effect on improving power performance. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides an amorphous carbon-coated phosphorus copper-doped hard carbon composite material and a preparation method thereof. Phosphorus copper compounds are deposited in a hard carbon precursor by a chemical precipitation method, and polymers are deposited by a gas atomization method. Carbonization obtains an amorphous carbon-coated phosphorus copper-doped hard carbon composite material, thereby improving the energy density and power performance of the composite material.

[0005] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0006] The present invention provides an amorphous carbon-coated phosphorus copper-doped hard carbon composite material, which has a core-shell structure. The core is a phosphorus copper-doped hard carbon composite material, and the shell is amorphous carbon. The composite material is spherical, with an average diameter of 3-8 μm and a shell thickness of 0.2-1 μm. The weight ratio of the core to the shell is 100:1-5. Based on the total weight of the core, phosphorus accounts for 1-5wt% and copper accounts for 1-5wt%.

[0007] Furthermore, the specific surface area of ​​the composite material is 5-10m 2 / g, pore volume is 0.01-0.1cm 3 / g.

[0008] The technical purpose of the first aspect of the present invention is to provide a method for preparing an amorphous carbon-coated phosphorus copper-doped hard carbon composite material, comprising:

[0009] Phosphoric acid and copper sulfate solution are mixed and dispersed to obtain solution A;

[0010] The resin is mixed with an ammonia solution and dispersed to obtain a suspension B;

[0011] The solution A and the suspension B are mixed and reacted, the product is filtered and dried, and then formaldehyde gas is introduced into the product to react and carbonize to obtain the phosphorus copper doped hard carbon composite material;

[0012] An organic polymer solution is sprayed onto the surface of the phosphorus copper doped hard carbon composite material, wherein the organic polymer solution is selected from at least one of xylene solutions of polyaniline, polythiophene, polypyrrole and polydopamine, and then carbonized to obtain an amorphous carbon-coated phosphorus copper doped hard carbon composite material.

[0013] Furthermore, the mass ratio of the phosphoric acid to the copper sulfate solution is 1:1-5; the solute mass concentration of the copper sulfate is 1-10wt%. More specifically, the phosphoric acid and the copper sulfate solution are mixed by adding the phosphoric acid to the copper sulfate solution.

[0014] Furthermore, the mass ratio of the resin to the ammonia solution is 1:5-10, and the mass concentration of the ammonia solution is 1-10 wt %. More specifically, the mixing of the two is performed by adding the resin to the ammonia solution.

[0015] Furthermore, the resin is selected from at least one of epoxy resin, polyurethane resin and furfural resin. The epoxy resin is at least one of bisphenol A epoxy resin, bisphenol F epoxy resin and bisphenol S epoxy resin;

[0016] Furthermore, solution A and suspension B are mixed and reacted in a mass ratio of 1-3:10. The pH of the mixture of solution A and suspension B is 9-11. The reaction temperature of the mixture of solution A and suspension B is 50-150° C., and the reaction time is 1-12 hours.

[0017] Furthermore, the step of introducing formaldehyde gas into the product to react is carried out in a tubular furnace at a temperature of 200-300° C. for 1-6 hours.

[0018] Furthermore, the carbonization after the introduction of formaldehyde is carried out at 700-1200° C. for 1-6 hours, followed by a natural cooling process to room temperature under an inert atmosphere.

[0019] Furthermore, the spraying of the organic polymer solution onto the surface of the phosphorus copper doped hard carbon composite material is carried out using an atomizing device, and the phosphorus copper doped hard carbon composite material is first heated to 50-150°C, the flow rate of the organic polymer solution is 10-50g / min / kg of the phosphorus copper doped hard carbon composite material, and the spraying time is 30-300min. After spraying the organic polymer solution, the steps of drying and crushing are also included, and then carbonization is carried out.

[0020] Furthermore, the concentration of the organic polymer solution is 1-10 wt%.

[0021] Furthermore, the carbonization after spraying the organic polymer solution is carried out at 500-700° C. for 1-6 hours.

[0022] The technical purpose of the second aspect of the present invention is to provide an amorphous carbon-coated phosphorus copper-doped hard carbon composite material prepared by the above preparation method.

[0023] The technical purpose of the third aspect of the present invention is to provide the application of the above-mentioned amorphous carbon-coated phosphorus copper-doped hard carbon composite material as a battery negative electrode material, especially a lithium-ion battery.

[0024] The implementation of the present invention will have the following beneficial effects:

[0025] (1) The core of the composite material prepared by the present invention is phosphorus copper doped hard carbon, and the outer layer is covered with amorphous carbon. The doping elements improve the conductivity and specific capacity of the material and have a higher initial efficiency.

[0026] (2) The present invention uses copper sulfate and ammonia as reactants to generate copper hydroxide through a chemical deposition reaction, which is then deposited on the resin surface or internal pores. After carbonization, copper doping is achieved to improve the electronic conductivity of the material. Phosphoric acid is doped into hard carbon to improve the specific capacity of the material by relying on the high specific capacity and pore-forming effect of phosphorus.

[0027] (3) The present invention uses a gas crosslinking agent, formaldehyde, to crosslink the material surface and create pores, which has the advantages of high efficiency and good uniformity compared to liquid phase crosslinking. At the same time, the gas crosslinking agent expands the carbon layer structure of the resin, increases the interlayer spacing, and improves the rate performance.

[0028] (4) The present invention adopts a spraying method to deposit polymer on the hard carbon composite material, which has the advantages of good uniformity, thin thickness, and high preparation efficiency. Amorphous carbon is obtained after the polymer is carbonized, which improves the initial efficiency of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] in:

[0031] Figure 1 This is an SEM image of the amorphous carbon-coated phosphorus copper-doped hard carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1

[0034] S1, adding 100 g of phosphoric acid to 300 g of a 5 wt% copper sulfate aqueous solution and uniformly dispersing the mixture to obtain a solution A;

[0035] 100 g of bisphenol A epoxy resin (CAS: 61788-97-4) was added to 800 g of a 5 wt% ammonia solution to obtain suspension B;

[0036] S2, adding 20 g of solution A to 100 g of solution B, and reacting at a temperature of 100°C for 6 h, then filtering, and vacuum drying at 80°C for 24 h. Then, the resulting material was transferred to a tube furnace, and formaldehyde gas was introduced and reacted at a temperature of 250°C for 3 h. Then, the temperature was raised to 900°C and carbonized for 3 h. The mixture was naturally cooled to room temperature under an argon atmosphere to obtain a phosphorus copper doped hard carbon composite material;

[0037] S3, transfer 1000 g of phosphorus copper doped hard carbon composite material to an atomizing device and heat it to 100°C, then spray the polyaniline solution (5 wt%) in xylene into the atomizing device through a vacuum flowmeter at 30 g / min for 60 minutes, then vacuum dry at 80°C for 24 hours, crush to a particle size D50 of 6 μm, and carbonize at 600°C for 3 hours to obtain an amorphous carbon-coated phosphorus copper doped hard carbon composite material.

[0038] Example 2

[0039] S1, adding 100 g of phosphoric acid to 100 g of a 10 wt% copper sulfate solution and uniformly dispersing the mixture to obtain a solution A;

[0040] 100 g of polyurethane resin was added to 500 g of a 10 wt% ammonia solution to obtain suspension B;

[0041] S2, adding 10 g of solution A to 100 g of solution B, and reacting at a temperature of 50°C for 12 h, then filtering, and vacuum drying at 80°C for 24 h. Then, the resulting material was transferred to a tube furnace, and formaldehyde gas was introduced, and the temperature was increased to 700°C for carbonization for 6 h, and then naturally cooled to room temperature under an argon atmosphere to obtain a phosphorus copper doped hard carbon composite material;

[0042] S3, transfer 1000g of phosphorus copper doped hard carbon composite material to an atomizing device and heat it to 50°C, then spray the polythiophene xylene solution (1wt%) into the atomizing device through a vacuum flowmeter at 10g / min for 300min, then vacuum dry at 80°C for 24h, crush to a particle size D50 of 6μm, and carbonize at 500°C for 6h to obtain an amorphous carbon-coated phosphorus copper doped hard carbon composite material.

[0043] Example 3

[0044] S1, adding 100 g of phosphoric acid to 500 g of 1 wt% copper sulfate solution and uniformly dispersing the mixture to obtain solution A;

[0045] 100 g of furfural resin was added to 1000 g of 1 wt% ammonia solution to obtain suspension B;

[0046] S2, adding 30 g of solution A to 100 g of solution B, and reacting at a temperature of 150°C for 1 hour, then filtering, and vacuum drying at 80°C for 24 hours. Then, the resulting material was transferred to a tube furnace, and formaldehyde gas was introduced and reacted at a temperature of 300°C for 1 hour. Then, the temperature was raised to 1200°C for carbonization for 1 hour, and the temperature was naturally cooled to room temperature under an argon atmosphere to obtain a phosphorus copper doped hard carbon composite material;

[0047] S3, transfer 1000g of phosphorus copper doped hard carbon composite material to an atomizing device and heat it to 150°C, then spray the polypyrrole solution (10wt%) of xylene into the atomizing device through a vacuum flowmeter at 50g / min for 30min, then vacuum dry at 80°C for 24h, crush to a particle size D50 of 6μm, and carbonize at 700°C for 1h to obtain an amorphous carbon-coated phosphorus copper doped hard carbon composite material.

[0048] Comparative Example 1

[0049] The difference from Example 1 is that phosphoric acid is not added, 300 g of a 5 wt % copper sulfate aqueous solution is used as solution A, and other operations and reaction conditions are the same as those in Example 1.

[0050] Comparative Example 2

[0051] 20g of phosphoric acid and 100g of epoxy resin were added to 500g of deionized water, mixed evenly, and transferred to a high-pressure reactor. The mixture was reacted at 100°C for 6h, then filtered and vacuum-dried at 80°C for 24h. The resulting material was then transferred to a tubular furnace, heated to 900°C for carbonization for 3h, and naturally cooled to room temperature under an argon atmosphere to obtain a phosphorus-doped hard carbon composite material.

[0052] Comparative Example 3

[0053] S1, preparation of copper phosphide composite material: weigh 6 g of copper sulfate, dissolve it in 100 g of 10 wt% ammonia solution and disperse it evenly, then add 1.5 g of red phosphorus, mix evenly, and add it to an autoclave. After reacting at 150° C. for 3 h, filter it, and vacuum dry it at 80° C. for 24 h to obtain a copper phosphide composite material;

[0054] S2, polyaniline-coated copper phosphide composite material: Weigh 50 g of the copper phosphide composite material prepared above and add it to 100 g of a 1 wt% aniline solution. Cyclic voltammetry is performed at -2 V to -2 V with a scan rate of 2 mV / s. After deposition for 50 cycles, the mixture is washed three times with 0.1 mol / L hydrochloric acid and dried in vacuo at 80°C for 24 h to obtain a polyaniline-coated copper phosphide composite material.

[0055] S3, preparation method of copper phosphide-doped hard carbon composite material: weigh 5g of the polyaniline-coated copper phosphide composite material prepared above, add it to 800g of butanediol and disperse it evenly, then add 100g of hard carbon and mix evenly, spray dry it, carbonize it at 700℃ for 3h, and then crush it to obtain the copper phosphide-doped hard carbon composite material.

[0056] Comparative Example 4

[0057] Weigh 6 g of copper sulfate and dissolve it in 100 g of a 10 wt% ammonia solution and disperse it evenly. Then add 1.5 g of red phosphorus, mix evenly, and add it to a high-pressure reactor. After reacting at 150 ° C for 3 hours, filter it, and vacuum dry it at 80 ° C for 24 hours to obtain a copper phosphide composite material; take 1000 g of the above copper phosphide composite material and transfer it to an atomizer and heat it to 100 ° C. Then, a xylene solution of polyaniline (5 wt%) is sprayed into the atomizer at 30 mL / min through a vacuum flowmeter for 60 minutes. The polyaniline solution is crushed and carbonized at 600 ° C for 3 hours to obtain an amorphous carbon-coated phosphorus copper-doped hard carbon composite material.

[0058] Performance tests of the materials prepared in the above examples and comparative examples:

[0059] (1) SEM test

[0060] The amorphous carbon-coated phosphorus copper-doped hard carbon composite material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 1 As shown. Figure 1 It can be seen that the composite material prepared in Example 1 has a spherical structure with uniform size distribution and a particle size ranging from 3 to 8 μm.

[0061] (2) Physical and chemical performance test

[0062] The composite materials prepared in the Examples and Comparative Examples were tested for particle size, tap density, specific surface area, and interlayer spacing. Interlayer spacing was measured using XRD, and all other test items were tested according to the national standard GBT-24533-2019, "Graphite Anode Materials for Lithium-ion Batteries." The test results are shown in Table 1.

[0063] Table 1

[0064]

[0065] (3) Button battery test

[0066] The composite materials described in the Examples and Comparative Examples were used as negative electrode materials for lithium-ion batteries assembled into button-type batteries. The negative electrode material preparation method involved adding a binder, a conductive agent, and a solvent to the composite material, stirring to form a slurry, coating the mixture on copper foil, and then drying and rolling the resulting mixture. The binder used was LA132, the conductive agent was SP, and the solvent was double-distilled water. A negative electrode sheet was prepared using a composite material composition of 95g SP:LA132:double-distilled water:1g:4g:220mL. A metallic lithium sheet served as the counter electrode. The electrolyte used was LiPF6 / EC+DEC, consisting of a 1:1 volume ratio of LiPF6 as the electrolyte and a 1.3 mol / L mixture of EC and DEC as the solvent. The electrolyte concentration was 1.3 mol / L. A polyethylene film was used as the separator. The button-type batteries were assembled in an argon-filled glove box. Electrochemical performance was measured on a Wuhan Landian CT2001A battery tester over a charge and discharge voltage range of 0.00V to 2.0V at a charge and discharge rate of 0.1C. The button cells' initial discharge capacity and efficiency were measured, along with rate performance (1C / 0.1C) and cycle performance (0.2C / 0.2C, 100 cycles). The test results are shown in Table 2.

[0067] Table 2

[0068]

[0069] It can be seen from Tables 1 and 2 that, compared with the comparative example, the first discharge capacity and first efficiency, rate performance and cycle performance of the negative electrode material prepared from the materials of the embodiments of the present invention are significantly improved. The reason is that, in the present invention, the hard carbon negative electrode material generates copper hydroxide on the hard carbon surface through a chemical reaction to improve the electronic conductivity of the material and improve the rate performance. At the same time, phosphorus doping improves the specific capacity of the material, and the gas atomization method is used to deposit a polymer on the hard carbon composite material to reduce its irreversible capacity and improve the first efficiency and cycle performance. In addition, phosphoric acid doping has the advantages of lower impedance than red phosphorus doping, thereby improving the rate performance.

[0070] (4) Soft pack battery test:

[0071] The composite materials in the examples and comparative examples were mixed and coated to prepare negative electrode sheets, and 2Ah soft-pack batteries were prepared using the ternary material (LiNi1 / 3Co1 / 3Mn1 / 3O2) as the positive electrode, LiPF6 (the solvent was EC+DEC, the volume ratio was 1:1, and the electrolyte concentration was 1.3 mol / L) as the electrolyte, and Celgard2400 membrane as the separator.

[0072] The rate performance of the soft-pack battery was tested over a charge and discharge voltage range of 2.75 to 4.2 V, at a temperature of 25 ± 3.0°C, with charging at 1.0C, 3.0C, 5.0C, 10.0C, and 20.C, and discharging at 1.0C. The results are shown in Table 3.

[0073] Table 3

[0074]

[0075]

[0076] As can be seen from Table 3, the rate charging performance of the soft-pack batteries prepared with the materials of Examples 1-3 is significantly better than that of the comparative example, that is, the charging time is shorter. The reason is that the carbon layer structure of the resin of the example materials is expanded by a gas cross-linking agent, thereby increasing the interlayer spacing and improving the rate performance, making it easier for lithium ions to be embedded, resulting in low impedance and small temperature rise.

[0077] (5) High-temperature storage test: The capacity of the battery in the fully charged state was tested at 60°C and was X1. After that, it was placed at 60°C for 30 days and the capacity of the battery was tested again and was X2. The charge retention rate was calculated as X2 / X1*100%. The battery was then fully charged to a fully charged state (100% SOC) and the capacity of the battery was tested as X3. The recovery capacity was calculated as X3 / X1*100%. The results are shown in Table 4.

[0078] Table 4

[0079]

[0080] As can be seen from Table 4, the embodiment material reduces its irreversible capacity and defects and improves storage performance due to the deposition of polymer on the hard carbon composite material by gas atomization.

[0081] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

[0082] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing an amorphous carbon-coated phosphorus copper-doped hard carbon composite material, comprising: Phosphoric acid and copper sulfate solution are mixed and dispersed to obtain solution A; The mass ratio of phosphoric acid and copper sulfate solution is 1:1-5; The solute mass concentration of the copper sulfate solution is 1-10wt%; The resin is mixed with an ammonia solution and dispersed to obtain a suspension B; the mass ratio of the resin to the ammonia solution is 1:5-10, and the mass concentration of the ammonia solution is 1-10wt%; The solution A and the suspension B are mixed and reacted in a mass ratio of 1-3:10; the pH of the mixture of the solution A and the suspension B is 9-11; the reaction temperature of the mixture of the solution A and the suspension B is 50-150° C., and the reaction time is 1-12 hours; the product is filtered and dried, and then formaldehyde gas is introduced into the product for reaction and carbonization to obtain the phosphorus copper doped hard carbon composite material; An organic polymer solution is sprayed onto the surface of the phosphorus copper doped hard carbon composite material, wherein the organic polymer solution is selected from at least one of xylene solutions of polyaniline, polythiophene, polypyrrole and polydopamine, and then carbonized to obtain an amorphous carbon-coated phosphorus copper doped hard carbon composite material.

2. The preparation method according to claim 1, characterized in that The resin is selected from at least one of epoxy resin, polyurethane resin and furfural resin.

3. The preparation method according to claim 1, characterized in that The reaction of introducing formaldehyde gas into the product is carried out in a tubular furnace at a temperature of 200-300° C. for 1-6 hours. The carbonization after the introduction of formaldehyde is carried out at a temperature of 700-1200° C. for 1-6 hours.

4. The preparation method according to claim 1, characterized in that The spraying of the organic polymer solution onto the surface of the phosphorus copper doped hard carbon composite material is carried out using an atomizing device, and the phosphorus copper doped hard carbon composite material is first heated to 50-150°C, the flow rate of the organic polymer solution is 10-50g / min / kg phosphorus copper doped hard carbon composite material, and the spraying time is 30-300min.

5. The preparation method according to claim 1, characterized in that The carbonization after spraying the organic polymer solution is carried out at 500-700° C. for 1-6 hours.

6. Use of the composite material prepared by the preparation method according to claim 1 as a negative electrode material for a battery.

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