A silver-doped hard carbon composite material and its preparation method

Abstract

The present invention relates to a silver-doped hard carbon composite material and a preparation method thereof. A preparation method of a silver-doped hard carbon composite material includes: (1) mixing an organic silver compound, an organic acid and an organic solvent to obtain a mixed solution; (2) using an electrochemical method, with an aminated resin as a working electrode, the mixed solution as a solvent, and a saturated calomel electrode as a counter electrode, after cyclic voltammetry scanning, washing and drying, a silver-doped hard carbon precursor material is obtained; (3) adding the silver-doped hard carbon precursor material to an organic solvent, mixing evenly, dropping a hydrazine reducing agent, performing ultrasonic dispersion, filtering and drying, and keeping warm at 700-1100 °C for 1-6 h in an inert atmosphere to obtain a silver-doped hard carbon composite material. For the silver-doped hard carbon composite material and the preparation method thereof according to the present invention, silver oxide is deposited in the pores of hard carbon by an electrochemical deposition method, so as to improve the doping uniformity, consistency and process controllability. Meanwhile, the reaction conditions are mild and the compatibility with the hard carbon precursor is good.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of lithium-ion battery materials, and particularly relates to a silver-doped hard carbon composite material and a preparation method thereof. Background Art

[0002] Hard carbon is an amorphous carbon that is difficult to graphitize. It has advantages such as zero expansion and excellent fast charging and low-temperature performance. However, due to the high porosity and specific surface area of hard carbon itself, the first efficiency of its materials is relatively low (about 80%), the high-temperature storage performance is poor, and the electronic conductivity is poor, which limits its application. One way to improve the first efficiency of the material is to reduce the porosity of the material, reduce side reactions, and improve the first efficiency, but this will reduce its kinetic performance. For example, by doping asphalt and carbonizing, doping trace metal elements (such as nano-silver, nano-copper, etc.), but due to the relatively large density of metal silver / copper itself, it is easy to cause poor uniformity between materials and affect its processing performance. At the same time, the nano-metal reacts violently with the electrolyte, resulting in a decline in its high-temperature storage.

[0003] In view of this, the present invention proposes a new silver-doped hard carbon composite material and a preparation method thereof. While doping metal elements to reduce the electron impedance, it has good processing performance and a simple preparation process, and can improve the first efficiency, power and other properties of the material. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a silver-doped hard carbon composite material. By using an electrochemical method to deposit an organic silver compound in the pores of porous hard carbon and performing reduction, a silver-doped hard carbon composite material can be obtained, which can improve the first efficiency and power performance of the hard carbon material.

[0005] In order to achieve the above purpose, the technical solution adopted is as follows:

[0006] A preparation method of a silver-doped hard carbon composite material, comprising the following steps:

[0007] (1) Mix an organic silver compound, an organic acid and an organic solvent evenly to obtain a mixed solution;

[0008] (2) Using an electrochemical method, with an aminated resin as the working electrode, the mixed solution as the solvent, and a saturated calomel electrode as the counter electrode, after scanning by cyclic voltammetry for 10 to 100 cycles, wash with 0.1 mol / L HCl and dry in vacuum to obtain a silver-doped hard carbon precursor material;

[0009] (3) Add the silver-doped hard carbon precursor material to an organic solvent, mix evenly, dropwise add a hydrazine-based reducing agent, perform ultrasonic dispersion treatment, filter and dry, keep it at 700-1100 °C for 1-6 h in an inert atmosphere, cool to room temperature, and pulverize to obtain the silver-doped hard carbon composite material.

[0010] Further, in the step (1), the organic silver compound is one of silver tetrafluoroborate, silver trifluoromethanesulfonate, silver trifluoroacetate, and silver hexafluorophosphate;

[0011] The organic acid is polystyrenesulfonic acid or polyvinylsulfonic acid;

[0012] The organic solvent is one of carbon tetrachloride, cyclohexane, xylene, and N-methylpyrrolidone.

[0013] Further, in the step (1), the mass ratio of the organic silver compound, the organic acid, and the organic solvent is 100:1 to 10:500 to 1000.

[0014] Further, in the step (2), the preparation method of the aminated resin is as follows: The resin is soaked in an acidic solution for 22 to 26 h, then added to an aniline solution, stirred and dispersed for 0.8 to 1.2 h, filtered and dried to obtain the aminated resin.

[0015] Still further, the resin is one of phenolic resin, furfural resin, and epoxy resin;

[0016] The acidic solution is one of sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid solution, and the mass concentration is 10 to 20 wt%.

[0017] Further, in the step (2), scanning is carried out under the conditions of -2V to 2V and 0.5 to 5 mV / s

[0018] Further, in the step (3), the hydrazine reducing agent is one of anhydrous hydrazine, methyl hydrazine, ethyl hydrazine, propyl hydrazine, and tert-butyl hydrazine.

[0019] Further, in the step (3), after ultrasonic dispersion for 1 to 6 h, filtration is carried out, and vacuum drying is carried out at 80 °C;

[0020] The temperature is raised to 700 to 1100 °C at a heating rate of 1 to 10 °C / min

[0021] Further, in the step (3), the mass ratio of the silver-doped hard carbon precursor material to the hydrazine reducing agent is 100:100 to 200.

[0022] Another object of the present invention is to provide a silver-doped hard carbon composite material, which is prepared by the above preparation method and has the advantages of good initial efficiency and power performance.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The present invention adopts electrochemical deposition to deposit silver compounds, which has the advantages of good uniformity, controllable process, high deposition density, high effect, etc.; compared with traditional solid / liquid phase doping, it has the advantages of excellent processing performance, high consistency, low impedance, etc., and reduces side reactions on the surface of the material and improves its power and other performance.

[0025] 2. The present invention uses a hydrazine reducing agent to reduce the silver compound to silver element, which has the advantages of mild conditions, controllable process, high consistency, etc., and improves the power and cycle performance of the hard carbon composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of the silver-doped hard carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0027] In order to further illustrate the silver-doped hard carbon composite material and its preparation method of the present invention and achieve the intended purpose of the invention, the following is a detailed description of the silver-doped hard carbon composite material and its preparation method according to the present invention, its specific implementation, structure, characteristics and efficacy in combination with the preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0028] The following will further introduce a silver-doped hard carbon composite material and a preparation method thereof in detail in conjunction with specific embodiments of the present invention:

[0029] The silver-doped hard carbon composite material and the preparation method thereof described in the present invention deposit silver oxide in the hard carbon pores by electrochemical deposition, and reduce the silver to be uniformly doped in the pores, and have the advantages of good doping uniformity, high consistency, and controllable process. At the same time, compared with direct doping with silver powder, organic silver has the advantages of mild reaction conditions and good compatibility with hard carbon precursors, which improves the consistency of the prepared materials and is applied to lithium-ion batteries to improve the power performance of the materials and their initial efficiency.

[0030] Example 1.

[0031] The specific steps are as follows:

[0032] (1) 100 g of phenolic resin was added to 1000 ml of 15 wt% sulfuric acid solution and soaked for 24 h, filtered to obtain a carboxylated resin; then 50 g of the carboxylated resin was added to 100 g of aniline solvent, stirred and dispersed evenly for 1 h, filtered, and vacuum dried at 80° C. for 24 h to obtain an amino resin.

[0033] (2) Mix 100 g of silver tetrafluoroborate, 5 g of polystyrene sulfonic acid with 800 g of carbon tetrachloride organic solvent evenly to obtain a mixed solution.

[0034] Afterwards, adopt the electrochemical method, use the aminated resin as the working electrode, the mixed solution as the solvent, and the saturated calomel as the counter electrode. Adopt cyclic voltammetry, scan for 50 cycles under the conditions of -2V to 2V and a scanning rate of 1 mV / s. Then wash with 0.1 mol / L HCl and dry in vacuum at 80 °C for 24 h to obtain the silver-doped hard carbon precursor material.

[0035] (3) Add 100 g of the silver-doped hard carbon precursor material to 500 g of carbon tetrachloride. After preparing the silver-doped hard carbon precursor material solution, add 150 g of methylhydrazine dropwise, carry out ultrasonic dispersion reaction for 3 h, then filter, and then dry in vacuum at 80 °C for 24 h. Then transfer it to a tubular furnace, under an argon inert atmosphere, with a heating rate of 5 °C / min, heat up to 900 °C and hold for 3 h. Then cool down to room temperature under an argon inert atmosphere and pulverize to obtain the silver-doped hard carbon composite material.

[0036] Example 2.

[0037] The specific operation steps are as follows:

[0038] (1) Add 100 g of furfural resin to 100 ml of 10 wt% nitric acid solution and soak for 24 h, then filter to obtain the carboxylated resin. Then take 50 g of the carboxylated resin and add it to 100 g of aniline solvent, stir and disperse evenly for 1 h, filter, and dry in vacuum at 80 °C for 24 h to obtain the aminated resin.

[0039] (2) Mix 100 g of silver trifluoromethanesulfonate, 1 g of polyethylene sulfonic acid with 500 g of cyclohexane evenly to obtain a mixed solution.

[0040] Afterwards, adopt the electrochemical method, use the aminated resin as the working electrode, the mixed solution as the solvent, and the saturated calomel as the counter electrode. Adopt cyclic voltammetry, scan for 10 cycles under the conditions of -2V to 2V and a scanning rate of 0.5 mV / s. Then wash with 0.1 mol / L HCl and dry in vacuum at 80 °C for 24 h to obtain the silver-doped hard carbon precursor material.

[0041] (3) Add 100 g of the silver-doped hard carbon precursor material to 500 ml of cyclohexane solvent. After preparing the silver-doped hard carbon precursor material solution, add 100 g of ethylhydrazine reducing agent dropwise, carry out ultrasonic dispersion reaction for 1 h, then filter, dry in vacuum at 80 °C for 24 h. Then transfer it to a tubular furnace, under an argon inert atmosphere, heat up to 700 °C at a heating rate of 1 °C / min and hold for 6 h. Then cool down to room temperature under an argon inert atmosphere and pulverize to obtain the silver-doped hard carbon composite material.

[0042] Example 3.

[0043] The specific operation steps are as follows:

[0044] (1) Add 100 g of epoxy resin to 1000 ml of 20 wt% hydrochloric acid solution and soak for 24 h, then filter to obtain carboxylated resin. After that, take 50 g of carboxylated resin and add it to 100 g of aniline solvent, stir and disperse evenly for 1 h, filter and dry in vacuum at 80 °C for 24 h to obtain amino resin.

[0045] (2) Mix 100 g of silver trifluoroacetate, 10 g of polystyrene sulfonic acid and 1000 g of xylene evenly to obtain a mixed solution.

[0046] Then, using the electrochemical method, with the amino resin as the working electrode, the mixed solution as the solvent, and saturated calomel as the counter electrode, cyclic voltammetry is used to scan 100 cycles under the conditions of -2V to 2V and a scanning rate of 5 mV / s. Then, wash with 0.1 mol / L HCl and dry in vacuum at 80 °C for 24 h to obtain a silver-doped hard carbon precursor material;

[0047] (3) Add 100 g of the silver-doped hard carbon precursor material to 500 ml of xylene solvent. After preparing the silver-doped hard carbon precursor material solution, add 200 g of tert-butylhydrazine reducing agent, ultrasonically disperse and react for 6 h, then filter and dry in vacuum at 80 °C for 24 h. Then transfer it to a tube furnace, under an inert atmosphere, with a heating rate of 10 °C / min, heat up to 1100 °C and hold for 1 h, and then cool to room temperature and crush under an argon inert atmosphere to obtain a silver-doped hard carbon composite material.

[0048] Example 4.

[0049] The specific operation steps are as follows:

[0050] (1) Add 100 g of phenolic resin to 1000 ml of 15 wt% phosphoric acid solution and soak for 22 - 26 h, then filter to obtain carboxylated resin; after that, take 50 g of carboxylated resin and add it to 100 g of aniline solvent, stir and disperse evenly for 1 h, filter and dry in vacuum at 80 °C for 24 h to obtain amino resin.

[0051] (2) Mix 100 g of silver hexafluorophosphate, 8 g of polystyrene sulfonic acid and 700 g of N-methylpyrrolidone evenly to obtain a mixed solution.

[0052] Then, using the electrochemical method, with the amino resin as the working electrode, the mixed solution as the solvent, and saturated calomel as the counter electrode, cyclic voltammetry is used to scan 40 cycles under the conditions of -2V to 2V and a scanning rate of 4 mV / s. Then, wash with 0.1 mol / L HCl and dry in vacuum at 80 °C for 24 h to obtain a silver-doped hard carbon precursor material;

[0053] (3) Add 100 g of the silver-doped hard carbon precursor material to 600 g of N-methylpyrrolidone. After preparing the silver-doped hard carbon precursor material solution, add 180 g of propylhydrazine dropwise, and carry out ultrasonic dispersion reaction for 3 h. Then filter and dry in vacuum at 80 °C for 24 h. Then transfer it to a tube furnace. Under an argon inert atmosphere, heat it at a heating rate of 5 °C / min to 1000 °C and hold for 4 h. Then cool it to room temperature under an argon inert atmosphere and crush it to obtain the silver-doped hard carbon composite material.

[0054] Comparative example:

[0055] Take 100 g of the aminated resin in step (1) of Example 1, mix it evenly with 10 g of silver trifluoroacetate, grind it, then transfer it to a tube furnace, and introduce tert-butylhydrazine reducing agent gas. Heat it at a heating rate of 5 °C / min to 900 °C and hold for 3 h. Then cool it to room temperature under an argon inert atmosphere and crush it to obtain the silver-doped hard carbon composite material.

[0056] Experimental test

[0057] 1. SEM test

[0058] Perform SEM test on the silver-doped hard carbon composite material prepared in Example 1. The results are as Figure 1 shown. The silver-doped hard carbon composite material prepared in Example 1 presents a spherical-like structure with uniform size distribution, and the particle size is 5 - 15 μm.

[0059] 2. Physical and chemical properties and coin cell test

[0060] Perform particle size, tapped density, specific surface area, elemental analysis and specific capacity tests on the silver-doped hard carbon composite materials prepared in Examples 1 - 3 and the comparative example. Test method: GBT - 24533-2019 "Graphite Anode Materials for Lithium-Ion Batteries".

[0061] The silver-doped hard carbon composite materials obtained in Examples 1 to 3 and the comparative example were assembled into coin cells A1, A2, A3, and B1 respectively; 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 obtained through drying and rolling. The binder used was LA132 binder, the conductive agent was SP, the negative electrode materials were the hard carbon fast-charging negative electrode materials prepared in Examples 1 to 3 and the comparative example respectively, the solvent was secondary distilled water, and the ratio was: negative electrode material: SP: LA132: secondary distilled water = 95 g: 1 g: 4 g: 220 mL, and the negative electrode sheets were prepared; the electrolyte was LiPF6 / EC + DEC (volume ratio 1:1, concentration 1.3 mol / L), the metal lithium sheet was the counter electrode, the separator was a polyethylene PE, polypropylene PP, or polyethylene-propylene PEP composite film, the simulation battery assembly was carried out in a glove box filled with argon, and the electrochemical performance was carried out on a Wuhan Blue Electric CT2001A battery tester, the charge-discharge voltage range was 0.00 V to 2.0 V, and the charge-discharge rate was 0.1 C. At the same time, the rate (2C / 0.1C) and cycle performance (0.2C / 0.2C, 200 times) of the coin cells were tested, and the test results are as follows in the table:

[0062] Table 1 Comparison of the physical and chemical properties of Examples 1 to 3 and the comparative example and their coin cells

[0063]

[0064]

[0065] It can be seen from Table 1 that compared with the comparative example, the first discharge capacity, first efficiency, rate performance, and cycle performance of the silver-doped hard carbon composite materials prepared in Examples 1 to 3 were significantly improved. The reason is that the present invention uses the electrochemical deposition method to prepare silver-doped hard carbon negative electrodes, uses silver doping to improve the electronic conductivity of the material, reduces the pores of the material to improve the first efficiency, reduces side reactions, and further improves the rate performance and cycle performance by silver doping.

[0066] 3. Soft-pack battery

[0067] Using the silver-doped hard carbon composite materials prepared in Examples 1 to 3 and the comparative example as the negative electrode materials, and preparing the negative electrode sheets, using ternary materials (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) as the positive electrode, using LiPF6 (the solvent is EC + DEC, volume ratio 1:1, concentration 1.3 mol / L) as the electrolyte, and celegard2400 as the separator to prepare 5Ah soft-pack batteries C1, C2, C3, and D1, that is, obtaining ternary lithium batteries, and carrying out the following tests.

[0068] Rate performance: The rate performance of the soft-pack battery was tested. The charge-discharge voltage range was 2.8 - 4.2 V, the temperature was 25 ± 3.0 °C. Charging was carried out at 1.0C, 3.0C, 5.0C, and 10.0C, and discharging was carried out at 1.0C. The results are shown in Table 2.

[0069] High-temperature storage: The test conditions were as follows: At 60 °C, the capacity of the battery in a fully charged state was X1. After placing it at 60 °C for 30 days, the capacity of the battery after placement was X2. The charge retention was calculated as X2 / X1 * 100%; then, the battery was fully charged to a fully charged state (100% SOC), and the capacity of the battery was X3. The recovery capacity was calculated as X3 / X1 * 100%; the results are shown in Table 3.

[0070] Table 2

[0071]

[0072]

[0073] As can be seen from the above table, the rate charging performance of the soft-pack batteries in Examples 1 - 3 is significantly better than that of the comparative examples, that is, the charging time of the soft-pack batteries in Examples 1 - 3 is shorter.

[0074] Table 3

[0075] Example Charge retention Capacity recovery Example 1 95.6％ 98.3％ Example 2 94.8％ 98.1％ Example 3 95.3％ 97.8％ Comparative example 94.8％ 96.1％

[0076] As can be seen from Table 3, due to the filling and doping of silver metal elements in the hard carbon in the example materials, the tap density is increased, the pores are reduced, the side reactions are reduced, and the high-temperature storage performance of the materials is improved, that is, the charge retention and capacity recovery of the battery are improved.

[0077] The above is only a preferred embodiment of the embodiments of the present invention, and does not impose any form of limitation on the embodiments of the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the embodiments of the present invention still fall within the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a silver-doped hard carbon composite material, characterized in that, The described preparation method comprises the following steps: (1) Mix an organic silver compound, an organic acid, and an organic solvent uniformly to obtain a mixed solution; (2) Using an electrochemical method, with an aminated resin as the working electrode, the mixed solution as the solvent, and a saturated calomel electrode as the counter electrode, after scanning by cyclic voltammetry for 10 - 100 cycles, wash with 0.1 mol / L HCl and dry under vacuum to obtain a silver-doped hard carbon precursor material; (3) Add the obtained silver-doped hard carbon precursor material to an organic solvent, mix well, dropwise add a hydrazine-based reducing agent, perform ultrasonic dispersion treatment, filter and dry, keep the temperature at 700 - 1100 °C for 1 - 6 h in an inert atmosphere, cool to room temperature, and pulverize to obtain the silver-doped hard carbon composite material.

2. The preparation method according to claim 1, wherein in the step (1), the organic silver compound is one of silver tetrafluoroborate, silver trifluoromethanesulfonate, silver trifluoroacetate, and silver hexafluorophosphate; the organic acid is polystyrenesulfonic acid or polyethylenesulfonic acid; the organic solvent is one of carbon tetrachloride, cyclohexane, xylene, and N-methylpyrrolidone.

3. The preparation method according to claim 1, wherein in the step (1), the mass ratio of the organic silver compound, the organic acid, and the organic solvent is 100:1 - 10:500 - 1000.

4. The preparation method according to claim 1, wherein the preparation method of the aminated resin in the step (2) is: soak the resin in an acidic solution for 22 - 26 h, add it to an aniline solution, stir and disperse for 0.8 - 1.2 h, filter and dry to obtain the aminated resin.

5. The preparation method according to claim 4, wherein the resin is one of phenolic resin, furfural resin, and epoxy resin; the acidic solution is one of sulfuric acid, nitric acid, phosphoric acid, and hydrochloric acid solution, with a mass concentration of 10 - 20 wt%.

6. The preparation method according to claim 1, wherein in the step (2), scan under the conditions of -2V - 2V and 0.5 - 5 mV / s.

7. The preparation method according to claim 1, wherein in the step (3), the hydrazine-based reducing agent is one of anhydrous hydrazine, methyl hydrazine, ethyl hydrazine, propyl hydrazine, and tert-butyl hydrazine.

8. The preparation method according to claim 1, wherein in the step (3), after ultrasonic dispersion for 1 - 6 h, filter and dry under vacuum at 80 °C; heat up to 700 - 1100 °C at a heating rate of 1 - 10 °C / min.

9. The preparation method according to claim 1, wherein in the step (3), the mass ratio of the silver-doped hard carbon precursor material to the hydrazine-based reducing agent is 100:100 - 200.

10. A silver-doped hard carbon composite material, characterized in that, The hard carbon composite material is prepared by the preparation method described in any one of claims 1 - 9.

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