A copper sulfide-doped carbon-based composite material, a preparation method thereof, and a sodium-ion battery

Abstract

This application relates to a copper sulfide-doped carbon-based composite material, a preparation method thereof, and a sodium-ion battery, belonging to the technical field of sodium-ion batteries. The copper sulfide-doped carbon-based composite material of this application has a core-shell structure. The inner core includes carbon material A, and copper sulfide is uniformly dispersed in the carbon material A. The outer shell includes carbon material B doped with phosphorus element, and the mass ratio of the outer shell to the inner core is 1-5:95-99. By doping copper sulfide into porous hard carbon in this application, copper sulfide has the characteristic of high electronic conductivity, which improves the electronic conductivity and ionic conductivity of the hard carbon composite material, and further improves the charge-discharge performance of the carbon composite material, especially the rate performance.

Description

Technical Field

[0001] The present invention relates to a copper sulfide-doped carbon-based composite material, a preparation method thereof, and a sodium-ion battery, belonging to the technical field of sodium-ion batteries. Background Art

[0002] Lithium-ion batteries are increasingly widely used in the field of electric vehicles. However, electric vehicles have higher and higher requirements for the performance of power batteries, and also have higher and higher requirements for cost control. Lithium-ion batteries consume a large amount of lithium resources, while the exploitable lithium resources on the earth are relatively limited, and the development of the power battery industry is gradually restricted by lithium resources.

[0003] Sodium has rich reserves and low prices, and sodium-ion batteries have been regarded as the most promising energy storage batteries to replace lithium-ion batteries. However, the energy density of sodium-ion batteries is relatively low, and the rate performance and cycle performance are poor. There is still a large room for improvement in application fields such as electric vehicle power batteries.

[0004] Currently, most of the research on sodium-ion batteries focuses on improving the mass specific capacity and initial efficiency of sodium-ion batteries. The negative electrode materials of sodium-ion batteries mainly use materials such as hard carbon, which have problems such as low specific capacity and low initial efficiency. The reason is that the porous structure of the material results in poor electronic conductivity. By coating or filling materials with high conductivity in the hard carbon material, on the one hand, it can reduce the electronic impedance of the material and improve the power, and on the other hand, it can reduce the pores of the material and improve the tap density of the material, and improve the storage and cycle performance of the material; there are also some that improve the capacity of the material by supplementing sodium sources in the carbon material.

[0005] The invention patent with the application publication number CN110690437A discloses a sodium supplement additive for the negative electrode of a sodium-ion battery, a negative electrode sheet of a sodium-ion battery, and a sodium-ion battery. It mainly uses sodium phosphide with a carbon-coated structure to supplement sodium to the negative electrode sheet of the sodium-ion battery, so that the negative electrode contains sodium, and compensates for the irreversible capacity loss in the first charge and discharge process of the sodium-ion battery. During the cycle of the sodium-ion battery, sodium phosphide can not only be used as a sodium source, but also participate in the cycle and provide part of the capacity as an active material.

[0006] However, this material coats the carbon material on the surface of sodium phosphide, and has little change in the internal pore structure of the carbon material, and has limited influence on the rate performance of the material. Summary of the Invention

[0007] The present invention provides a copper sulfide-doped carbon-based composite material, a preparation method thereof, and a sodium-ion battery to improve the rate performance of the carbon material used in sodium-ion batteries.

[0008] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0009] A copper sulfide-doped carbon-based composite material, characterized in that the copper sulfide-doped carbon-based composite material has a core-shell structure, the inner core includes carbon material A, copper sulfide is uniformly dispersed in the carbon material A, the outer shell includes carbon material B doped with phosphorus element, and the mass ratio of the outer shell to the inner core is 1-5:95-99.

[0010] The carbon material B is amorphous carbon.

[0011] A preparation method of a copper sulfide-doped carbon-based composite material includes the following steps:

[0012] 1) Mix phenolic resin, copper sulfide, and an auxiliary agent evenly in an organic solvent, then react for 1-6 h under the conditions of a temperature of 100-200 °C and a pressure of 1-6 MPa, perform solid-liquid separation, and freeze-dry the solid to obtain a precursor material; the auxiliary agent is at least one of ammonium persulfate, performic acid, benzoyl peroxide, and cyclohexanone peroxide;

[0013] 2) React the precursor material prepared in step 1) with a phosphorus-containing compound at 700-1100 °C for 10-60 min, and then react with a carbon source gas at 700-1100 °C for 1-6 h, and then cool to obtain; the phosphorus-containing compound is at least one of phosphine, phosphorus trichloride, phosphorus pentachloride, phosphorus pentoxide, hypophosphorous acid, phosphinic acid, metaphosphoric acid, tripolyphosphoric acid, pyrophosphoric acid, and polyphosphoric acid; the carbon source gas is at least one of methane and acetylene.

[0014] The phenolic resin in step 1) is a powder with a particle size of 100-1000 nm. Preferably 100-500 nm, more preferably 100-200 nm, and further preferably 100 nm.

[0015] The organic solvent in step 1) is at least one of ethanol, acetone, methanol, ethylene glycol, and butanol.

[0016] The mass ratio of the phenolic resin to copper sulfide in step 1) is 100:10-30.

[0017] The mass ratio of the phenolic resin to the auxiliary agent in step 1) is 100:1-5.

[0018] The mass ratio of the phenolic resin to the organic solvent in step 1) is 1-5:95-99.

[0019] In step 1), mixing the phenolic resin, copper sulfide, and the auxiliary agent evenly in the organic solvent means adding the copper sulfide and the auxiliary agent to the organic solvent mixture of the phenolic resin.

[0020] The temperature of freeze-drying in step 1) is -40~-50 °C; the time of freeze-drying is 24-48 h.

[0021] The reaction of the precursor material in step 2) with a phosphorus-containing compound at 700 - 1100 °C for 10 - 60 min is to add the precursor material into a tube furnace, then introduce an inert gas to discharge air, heat up to 700 - 110 °C under the inert gas, and then introduce the phosphorus-containing compound gas to keep warm for 10 - 60 min. The flow rate of the phosphorus-containing compound gas introduced is 1 - 10 mL / min. Preferably, the flow rate introduced is 1 - 5 mL / min. After introducing the phosphorus-containing compound gas and keeping warm for 10 - 60 min, stop introducing the phosphorus-containing compound gas, then keep the temperature unchanged and introduce the carbon source gas for 1 - 6 h. The flow rate of the carbon source gas introduced is 20 - 50 mL / min. The time for introducing the carbon source gas is preferably 3 - 6 h.

[0022] The phosphorus-containing compound gas is prepared by heating the phosphorus-containing compound in a heating tube to form the phosphorus-containing compound gas.

[0023] The cooling in step 2) is to cool down in an inert gas atmosphere.

[0024] The inert gas in step 2) is any one of argon and nitrogen.

[0025] A sodium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode material layer provided on the surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, and the negative electrode active material is the above-mentioned copper sulfide-doped carbon-based composite material.

[0026] Advantages of this application:

[0027] 1) In this application, by doping copper sulfide in porous hard carbon, copper sulfide has the characteristics of high electronic conductivity, which improves the electronic conductivity and ionic conductivity of the hard carbon composite material, and further improves the charge and discharge performance of the carbon composite material, especially the rate performance. At the same time, copper sulfide has the characteristic of high tap density, which can also improve the tap density of the material.

[0028] 2) In this application, by doping phosphorus compounds in the pores of carbon through the gasification method, not only can the specific capacity of the material be improved, but also the rate performance of the carbon material can be improved. Compared with the solid-phase method of doping phosphorus compounds, the carbon composite material prepared in this application has the characteristics of good uniformity, high consistency, and a high binding force between the phosphorus compound and the carbon-based material after gasification.

[0029] 3) In the preparation of the carbon composite material of this application, through the hydrothermal reaction, copper sulfide can be uniformly doped in the porous carbon precursor, and the prepared composite material has a uniform particle size and uniform particles. And the additives in the material can make the organic matter form a three-dimensional network structure, while increasing the layer spacing of the material and reducing the impedance. Description of the drawings

[0030] Figure 1SEM image of the copper sulfide doped carbon-based composite material of Embodiment 1 of the present invention. Detailed implementation manners

[0031] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention easier to understand, the present invention will be described in detail below in conjunction with specific implementation manners.

[0032] Embodiment 1

[0033] The preparation method of the copper sulfide doped carbon-based composite material of this embodiment includes the following steps:

[0034] 1) Grind 100 g of phenolic resin until the particle size is 500 nm, and then add the phenolic resin into ethylene glycol to obtain a phenolic resin solution with a mass fraction of 2 wt%;

[0035] 2) Add 20 g of copper sulfide and 2 g of ammonium persulfate to the phenolic resin solution prepared in step 1), disperse evenly, then transfer to a high-pressure reaction kettle, and react for 3 h under the conditions of a temperature of 150 °C and a pressure of 3 MPa. Then filter, and freeze-dry the solid at -40 °C for 24 h to obtain the precursor material A;

[0036] 3) Transfer the precursor material A prepared in step 2) to a tubular furnace, introduce argon to remove the air in the tube, and then heat up to 950 °C; then introduce phosphine gas into the tubular furnace, and the flow rate during introduction is 5 mL / min, and the introduction time is 30 min; then stop introducing phosphine gas, change to introduce methane gas, and keep the temperature for 3 h, and then introduce argon and cool down to room temperature in an argon atmosphere, and crush the solid to obtain it.

[0037] The copper sulfide doped carbon-based composite material of this embodiment is prepared by the above method.

[0038] Embodiment 2

[0039] The preparation method of the copper sulfide doped carbon-based composite material of this embodiment includes the following steps:

[0040] 1) Grind 100 g of phenolic resin until the particle size is about 100 nm, and then add the phenolic resin into butanol to obtain a phenolic resin solution with a mass fraction of 1 wt%;

[0041] 2) Add 10 g of copper sulfide and 1 g of peracetic acid to the phenolic resin solution prepared in step 1), disperse evenly, then transfer to a high-pressure reaction kettle, and react for 1 h under the conditions of a temperature of 100 °C and a pressure of 6 MPa. Then filter, and freeze-dry the solid at -40 °C for 24 h to obtain the precursor material A;

[0042] 3) Transfer the precursor material A prepared in step 2) into a tube furnace, introduce argon to remove the air in the tube, and then heat up to 700 °C. Then introduce phosphorus trichloride gas into the tube furnace (heat phosphorus trichloride to 100 °C in the heating tube before introducing), with a flow rate of 1 mL / min during introduction and an introduction time of 10 min. Then stop introducing phosphorus trichloride gas, switch to introducing acetylene gas, and keep it warm for 1 h. Then introduce argon and cool down to room temperature under an argon atmosphere, and crush the solid to obtain the product.

[0043] The copper sulfide-doped carbon-based composite material of this example is prepared by the above method.

[0044] Example 3

[0045] The preparation method of the copper sulfide-doped carbon-based composite material of this example includes the following steps:

[0046] 1) Grind 100 g of phenolic resin until the particle size is about 100 nm, and then add the phenolic resin to methanol to obtain a phenolic resin solution with a mass fraction of 5 wt%.

[0047] 2) Add 30 g of copper sulfide and 5 g of cyclohexanone peroxide to the phenolic resin solution prepared in step 1), disperse evenly, and then transfer it to a high-pressure reactor. React under the conditions of a temperature of 200 °C and a pressure of 1 MPa for 1 h, and then filter. The solid is freeze-dried at -40 °C for 24 h to obtain the precursor material A.

[0048] 3) Transfer the precursor material A prepared in step 2) into a tube furnace, introduce argon to remove the air in the tube, and then heat up to 1100 °C. Then introduce phosphorus pentachloride gas into the tube furnace, with a flow rate of 10 mL / min during introduction and an introduction time of 60 min. Then stop introducing phosphorus pentachloride gas, switch to introducing methane gas, and keep it warm for 6 h. Then introduce argon and cool down to room temperature under an argon atmosphere, and crush the solid to obtain the product.

[0049] The copper sulfide-doped carbon-based composite material of this example is prepared by the above method.

[0050] Example 4

[0051] The preparation method of the copper sulfide-doped carbon-based composite material of this example includes the following steps:

[0052] 1) Grind 100 g of phenolic resin until the particle size is about 100 nm, and then add the phenolic resin to butanol to obtain a phenolic resin solution with a mass fraction of 2 wt%.

[0053] 2) Add 20 g of copper sulfide and 3.5 g of benzoyl peroxide to the phenolic resin solution prepared in step 1), disperse evenly, then transfer to a high-pressure reactor, and react for 2.5 h under the conditions of a temperature of 200 °C and a pressure of 2 MPa. Then filter, and freeze-dry the solid at -40 °C for 24 h to obtain the precursor material A;

[0054] 3) Transfer the precursor material A prepared in step 2) to a tube furnace, introduce argon to remove the air in the tube, and then heat up to 900 °C; then introduce metaphosphoric acid gas into the tube furnace (heat metaphosphoric acid to 250 °C in the heating tube and then introduce it), the flow rate during introduction is 8 mL / min, and the introduction time is 60 min; then stop introducing metaphosphoric acid gas, change to acetylene gas, and keep warm for 6 h, then introduce argon and cool down to room temperature in an argon atmosphere, and crush the solid to obtain the product.

[0055] The copper sulfide-doped carbon-based composite material of this example is prepared by the above method.

[0056] Example 5

[0057] In the preparation method of the copper sulfide-doped carbon-based composite material of this example, step 3) is as follows:

[0058] 3) Transfer the precursor material A prepared in step 2) to a tube furnace, introduce argon to remove the air in the tube, and then heat up to 1100 °C; then introduce pyrophosphoric acid gas into the tube furnace (heat metaphosphoric acid to 400 °C in the heating tube and then introduce it), the flow rate during introduction is 8 mL / min, and the introduction time is 60 min; then stop introducing pyrophosphoric acid gas, change to acetylene gas, and keep warm for 6 h, then introduce argon and cool down to room temperature in an argon atmosphere, and crush the solid to obtain the product.

[0059] The rest is the same as that in Example 4.

[0060] Comparative Example 1

[0061] The preparation method of the carbon-based composite material in this comparative example includes the following steps:

[0062] 1) Grind 100 g of phenolic resin to a particle size of about 500 nm, and then add the phenolic resin to ethylene glycol to obtain a phenolic resin solution with a mass fraction of 2 wt%;

[0063] 2) Transfer the phenolic resin solution prepared in step 1) to a high-pressure reactor, react for 3 h under the conditions of a temperature of 150 °C and a pressure of 3 MPa, then filter, and freeze-dry the solid at -40 °C for 24 h to obtain the precursor material;

[0064] 3) Transfer the precursor material obtained in step 2) into a tube furnace, introduce argon to remove the air in the tube, then heat up to 950 °C and hold for 3 h, then introduce argon and cool down to room temperature under an argon atmosphere, and crush the solid to obtain the product.

[0065] The carbon-based composite material of this comparative example was prepared by the above preparation method.

[0066] Comparative Example 2

[0067] The preparation method of the carbon-based composite material of this comparative example includes the following steps:

[0068] 1) Grind 100 g of phenolic resin until the particle size reaches 500 nm, and then add the phenolic resin into ethylene glycol to obtain a phenolic resin solution with a mass fraction of 2 wt%.

[0069] 2) Add 20 g of copper sulfide and 2 g of ammonium persulfate to the phenolic resin solution obtained in step 1), disperse evenly, then transfer it to a high-pressure reactor, react for 3 h under the conditions of a temperature of 150 °C and a pressure of 3 MPa, then filter, and freeze-dry the solid at -40 °C for 24 h to obtain the precursor material.

[0070] 3) Transfer the precursor material obtained in step 2) into a tube furnace, introduce argon to remove the air in the tube, then heat up to 900 °C and hold for 3 h, then introduce argon and cool down to room temperature under an argon atmosphere, and crush the solid to obtain the product.

[0071] Experimental Example

[0072] 1) SEM test

[0073] Perform SEM test on the composite material prepared in Example 1, and the results are as Figure 1 shown.

[0074] It can be seen from Figure 1 that the obtained composite material presents a granular structure with a particle size between 5 - 10 µm.

[0075] 2) Physical and chemical tests

[0076] Take the composite materials prepared in Examples 1 - 5 and Comparative Examples 1 - 2, and test their D002, specific surface area, tapped density and specific surface area according to the national standard GBT - 24533 - 2019 "Graphite Anode Materials for Lithium-Ion Batteries". The results are shown in Table 1.

[0077] Table 1 Comparison of physical and chemical test results

[0078] D002 (nm) Specific surface area (m2 / g) <![CDATA[Tap density (g / cm 3 ).]]> Powder conductivity (S / cm) Example 1 0.389 12.4 0.88 67 Example 2 0.387 11.8 0.82 65 Example 3 0.385 12.7 0.80 61 Example 4 0.384 12.1 0.89 60 Example 5 0.382 11.6 0.90 62 Comparative Example 1 0.379 11.1 0.72 23 Comparative Example 2 0.378 7.8 0.71 34

[0079] As can be seen from Table 1, the carbon composite material of this application has regular morphology, uniform particles, and an overall approximate spherical structure. The carbon composite material of this application is superior to the comparative example in terms of tap density and specific surface area, indicating that the preparation process of this application has a certain promoting effect on the refinement of the particle size of the carbon composite material.

[0080] 3) Coin cell test

[0081] Take the composite materials prepared in Examples 1-5 and Comparative Examples 1-2 as the negative electrode active material, and mix them evenly according to the mass ratio of negative electrode active material, CMC, SBR, SP, and H2O of 95:2.5:1.5:1:150, make a slurry, coat it on the negative electrode current collector, dry it, slice it, and prepare a negative electrode sheet. Then, use a sodium sheet as the positive electrode sheet, and the electrolyte is a 1mol / L bis(trifluoromethylsulfonyl)imide solution, where the solvent is a mixture of 1,3-epoxypentane and ethylene glycol dimethyl ether mixed according to a volume ratio of 1:1. NaNO3 is also added to the electrolyte as an additive, and the concentration of NaNO3 in the electrolyte is 0.1mol / L. The separator uses a composite membrane of polyethylene PE, polypropylene PP, and polyethylene-propylene PEP.

[0082] The coin cell assembly is carried out in a glove box filled with argon, and the electrochemical performance is tested on a Wuhan Blue Electric CT2001A battery tester. The charge-discharge voltage range is controlled at 0-2.5V, and the charge-discharge rate is 0.1C. The finally assembled coin cells are respectively marked as A1, A2, A3, A4, A5 and B1, B2. At the same time, the specific capacity of the battery under a 2C rate discharge is tested, and the rate performance (2C / 0.1C) is calculated.

[0083] Table 2 Comparison of electrochemical performance test results

[0084] Initial discharge capacity (mAh / g) Initial efficiency (%) Rate performance (2C / 0.1C) Example 1 328.2 90.4 91.2 Example 2 316.7 89.4 90.8 Example 3 312.8 89.5 90.3 Example 4 310.5 89.4 90.7 Example 5 308.7 89.5 90.6 Comparative Example 1 269.5 84.4 84.2 Comparative Example 2 255.4 83.2 82.9

[0085] As can be seen from Table 1, the carbon composite material of this application has a large initial discharge capacity and excellent rate discharge performance. The reason may be that the doping of copper sulfide can improve the electronic conductivity of the material, reduce its side reactions, and improve the specific capacity and initial efficiency of the material; at the same time, by doping phosphorus compounds into the pores of hard carbon through the gasification method, the specific capacity of the material is further improved and the rate performance is improved.

Claims

1. A preparation method of a copper sulfide-doped carbon-based composite material, characterized in that, It includes the following steps: 1) Mix phenolic resin, copper sulfide, and an auxiliary agent evenly in an organic solvent, and then react for 1 - 6 h under the conditions of a temperature of 100 - 200 °C and a pressure of 1 - 6 MPa. Perform solid-liquid separation, and freeze-dry the solid to obtain a precursor material; the auxiliary agent is at least one of ammonium persulfate, performic acid, benzoyl peroxide, and cyclohexanone peroxide; 2) React the precursor material prepared in step 1) with a phosphorus-containing compound at 700 - 1100 °C for 10 - 60 min, and then react with a carbon source gas at 700 - 1100 °C for 1 - 6 h, and then cool to obtain the product; the phosphorus-containing compound is at least one of phosphine, phosphorus trichloride, phosphorus pentachloride, phosphorus pentoxide, hypophosphorous acid, metaphosphorous acid, metaphosphoric acid, tripolyphosphoric acid, pyrophosphoric acid, and polyphosphoric acid; the carbon source gas is at least one of methane and acetylene.

2. The preparation method of the copper sulfide-doped carbon-based composite material according to claim 1, characterized in that, The phenolic resin in step 1) is a powder with a particle size of 100 - 1000 nm.

3. The preparation method of the copper sulfide-doped carbon-based composite material according to claim 1, characterized in that, The organic solvent in step 1) is at least one of ethanol, acetone, methanol, ethylene glycol, and butanol.

4. The preparation method of the copper sulfide-doped carbon-based composite material according to claim 1, characterized in that, The mass ratio of the phenolic resin to copper sulfide in step 1) is 100:10 - 30.

5. The preparation method of the copper sulfide-doped carbon-based composite material according to claim 4, wherein The mass ratio of the phenolic resin to the auxiliary agent in step 1) is 100:1 - 5.

6. The preparation method of the copper sulfide-doped carbon-based composite material according to claim 1, characterized in that, In step 1), mixing the phenolic resin, copper sulfide, and the auxiliary agent evenly in the organic solvent means adding the copper sulfide and the auxiliary agent to the organic solvent mixture of the phenolic resin.

7. The preparation method of the copper sulfide-doped carbon-based composite material according to claim 1, characterized in that, The temperature of freeze-drying in step 1) is -40 - 50 °C, and the time of freeze-drying is 24 - 48 h.

8. The preparation method of the copper sulfide-doped carbon-based composite material according to any one of claims 1-7, characterized in that, In step 2), reacting the precursor material with the phosphorus-containing compound at 700 - 1100 °C for 10 - 60 min means adding the precursor material into a tubular furnace, then introducing an inert gas to discharge air, heating to 700 - 110 °C under the inert gas, and then introducing the phosphorus-containing compound gas to keep warm for 10 - 60 min.

9. A sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The negative electrode includes a negative electrode current collector and a negative electrode material layer provided on the surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, and the negative electrode active material is a copper sulfide-doped carbon-based composite material prepared by the preparation method described in claim 1.

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