A phosphorus-silver-silicon co-doped hard carbon composite material and a preparation method thereof
By using a core-shell structure of phosphorus-silver-silicon co-doped hard carbon composite material and an electrochemical deposition method, the problems of low initial efficiency and increased impedance of hard carbon materials have been solved, thereby improving the energy density and power performance of lithium-ion batteries and making them suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUIYANG (GUIZHOU) NEW ENERGY MATERIALS CO LTD
- Filing Date
- 2023-05-22
- Publication Date
- 2026-05-12
AI Technical Summary
Hard carbon materials have a high specific surface area due to their porous structure, resulting in low initial efficiency. Furthermore, the impedance increases and the voltage plateau rises after doping with phosphorus, nitrogen, and silicon, which affects power performance.
A core-shell structure is adopted using a phosphorus-silver-silicon co-doped hard carbon composite material. The core is silver, phosphorus, and silicon-doped hard carbon, and the outer shell is amorphous carbon and lithium salt compounds. It is prepared by high-energy ball milling, spray drying and electrochemical deposition to improve electronic conductivity and ionic conductivity.
It improves the material's energy density, power performance, and cycle performance, while reducing impedance, making it suitable for industrial production.
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Figure CN116565168B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery material preparation, specifically a phosphorus-silver-silicon co-doped hard carbon composite material, and also relates to a method for preparing the phosphorus-silver-silicon co-doped hard carbon composite material. Background Technology
[0002] Hard carbon materials are used in 48V, HEV and sodium-ion batteries due to their advantages such as zero expansion, excellent low-temperature performance and good fast charging performance. However, due to the porous structure of hard carbon, the high specific surface area results in a low initial efficiency (80%) and a specific capacity of about 300 mAh / g, which is much lower than the capacity of graphite (355 mAh / g) and silicon-oxygen (1600 mAh / g).
[0003] To address this issue, current methods often involve doping hard carbon materials and creating pores, such as doping with phosphorus, nitrogen, and silicon. While doping increases the energy density of the material, it also increases impedance, leading to a higher voltage plateau. Therefore, it is necessary to dope with some metal elements with high electronic conductivity to reduce the impedance of the material and improve its power performance. Summary of the Invention
[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a phosphorus-silver-silicon co-doped hard carbon composite material with improved ionic conductivity, initial efficiency, and cycling performance.
[0005] Another object of the present invention is to provide a method for preparing the phosphorus-silver-silicon co-doped hard carbon composite material.
[0006] The present invention discloses a phosphorus-silver-silicon co-doped hard carbon composite material, which exhibits a core-shell structure. The core is silver, phosphorus, and silicon doped hard carbon, and the outer shell is composed of amorphous carbon and lithium salt compounds. The outer shell accounts for 1-10 wt% of the composite material by mass ratio of 100%.
[0007] The present invention discloses a method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material, comprising the following steps:
[0008] Step S1: Add micron-sized silicon to a high-energy ball mill and grind for 12-72 hours according to the mass ratio of silver powder: red phosphorus: nano silicon = 1-5: 10: 1-5 to obtain nano silicon with a particle size of 100-200nm. After obtaining nano silicon, continue to add red phosphorus and silver powder to the ball mill and grind for 12-72 hours. Then, vacuum dry at 80℃ for 24 hours to obtain a silver / phosphorus / silicon composite material.
[0009] Step S2: Dissolve the resin in an organic solvent according to the mass ratio of resin: organic solvent: silver / phosphorus / silicon composite material = 100:500-1500:1-10, then add the silver / phosphorus / silicon composite material and perform ultrasonic dispersion (ultrasonic frequency of 25KHz, dispersion speed of 5000r / min, dispersion time of 60min). Obtain the precursor material by spray drying (inlet air temperature of 200℃, flow rate of 60mL / min, outlet air temperature of 80℃). Transfer the precursor material to a tube furnace and carbonize it at 600-1000℃ for 1-6h under an inert atmosphere to obtain an amorphous carbon-coated silver / phosphorus / silicon composite material.
[0010] Step S3: According to the mass ratio of amorphous carbon-coated silver / phosphorus / silicon composite material: binder = 100: 1-10, the amorphous carbon-coated silver / phosphorus / silicon composite material and binder are mixed and pressed into a block structure as the working electrode, and a saturated calomel electrode is used as the counter electrode. At the same time, 0.1 mol / L lithium difluorodioxarate phosphate in ethylene carbonate is prepared. Lithium salt is deposited on the surface of the working electrode by electrochemical deposition. After the deposition time is 10-120 min, it is washed 1-5 times with 1 mol / L hydrochloric acid, vacuum dried at 80℃ for 24 h, and carbonized at 700-1000℃ for 1-6 h to obtain a phosphorus-silver-silicon co-doped hard carbon composite material.
[0011] The above-mentioned method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material, wherein: the resin in step S2 is one of phenolic resin, furfural resin or epoxy resin; and the organic solvent is one of chloroform, toluene, acetone or xylene.
[0012] The above-mentioned method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material, wherein the binder in step S2 is one of polyvinyl alcohol, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, or sodium carboxymethyl cellulose.
[0013] The above-mentioned method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material, wherein: the electrochemical deposition method in step S3 is one of cyclic voltammetry, constant voltage method, constant current method, or pulse method; the parameters for cyclic voltammetry are -2V to 2V, 0.5-5mV / s; the parameters for constant voltage method are 2V; and the parameters for constant current method are 1-10mA / cm. 2 .
[0014] Compared with existing technologies, this invention has significant advantages. As can be seen from the above technical solution: this invention improves electronic conductivity by doping red phosphorus with silver powder and increases energy density with silicon powder, while leveraging the advantages of red phosphorus materials such as high energy density, high first-pass efficiency, and low cost to prepare a composite. A hard carbon precursor is then coated onto its surface to enhance the energy density and power performance of the hard carbon material. Lithium salt is deposited on the surface of the hard carbon precursor material via electrochemical deposition to improve the ionic conductivity and first-pass efficiency of the material, and to enhance cycle performance. Furthermore, the preparation process is simple, low-cost, and suitable for industrial production. Attached Figure Description
[0015] Figure 1 The image shows a SEM image of the phosphorus-silver-silicon co-doped hard carbon composite material prepared in Example 1. Detailed Implementation
[0016] Example 1:
[0017] A method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material includes the following steps:
[0018] Step S1: Add 3g of micron-sized silicon to a high-energy ball mill and grind for 48h to obtain nano-sized silicon with a particle size of 150nm. Add 10g of red phosphorus, 3g of silver powder and 500g of ethanol, and grind in a ball mill for 48h. Then vacuum dry at 80℃ for 24h to obtain a silver / phosphorus / silicon composite material.
[0019] Step S2: Dissolve 100g of phenolic resin in 1000g of chloroform, add 5g of silver / phosphorus / silicon composite material and ultrasonically disperse (ultrasonic frequency 25KHz, dispersion speed 5000r / min, dispersion time 60min), and obtain precursor material by spray drying (inlet air temperature 200℃, flow rate 60mL / min, outlet air temperature 80℃). Transfer the precursor material to a tube furnace and carbonize it at 800℃ for 3h under an argon inert atmosphere to obtain amorphous carbon-coated silver / phosphorus / silicon composite material.
[0020] Step S3: 100g of amorphous carbon-coated silver / phosphorus / silicon composite material was mixed with 5g of polyvinyl alcohol and pressed into a block structure as the working electrode, and a saturated calomel electrode was used as the counter electrode. At the same time, 0.1mol / L lithium difluorodioxarate phosphate in ethylene carbonate was prepared. Lithium salt was deposited on the surface of the working electrode by cyclic voltammetry in a voltage range of -2V to 2V and a surface sweep rate of 1mV / S for 60min. The electrode was washed three times with 1mol / L hydrochloric acid, vacuum dried at 80℃ for 24h, and carbonized at 800℃ for 3h to obtain the phosphorus-silver-silicon co-doped hard carbon composite material.
[0021] Example 2
[0022] A method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material includes the following steps:
[0023] Step S1: Add 1g of micron-sized silicon to a high-energy ball mill and grind for 12h to obtain nano-sized silicon with a particle size of 100nm. Add 10g of red phosphorus, 1g of silver powder and 500g of ethanol, and grind in a ball mill for 12h. Dry under vacuum at 80℃ for 24h to obtain a silver / phosphorus / silicon composite material.
[0024] Step S2: Dissolve 100g of phenolic resin in 500g of toluene organic solvent, add 1g of silver / phosphorus / silicon composite material and ultrasonically disperse (ultrasonic frequency 25KHz, dispersion speed 5000r / min, dispersion time 60min), and obtain precursor material by spray drying (inlet air temperature 200℃, flow rate 60mL / min, outlet air temperature 80℃). Transfer the precursor material to a tube furnace and carbonize it at 600℃ for 6h under an argon inert atmosphere to obtain amorphous carbon-coated silver / phosphorus / silicon composite material.
[0025] Step S3: 100g of amorphous carbon-coated silver / phosphorus / silicon composite material was mixed with 1g of polyacrylic acid binder and pressed into a block structure as the working electrode, and a saturated calomel electrode was used as the counter electrode. At the same time, 0.1mol / L lithium difluorodioxarate phosphate in ethylene carbonate was prepared. Lithium salt was deposited on the surface of the working electrode by electrochemical deposition for 10min. The electrode was washed once with 1mol / L hydrochloric acid, vacuum dried at 80℃ for 24h, and carbonized at 700℃ for 6h to obtain a phosphorus-silver-silicon co-doped hard carbon composite material.
[0026] Example 3
[0027] A method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material includes the following steps:
[0028] Step S1: Add 5g of micron-sized silicon to a high-energy ball mill and grind for 72h to obtain nano-sized silicon with a particle size of 200nm. Add 10g of red phosphorus, 5g of silver powder and 500g of ethanol, and grind in a ball mill for 72h. Dry under vacuum at 80℃ for 24h to obtain a silver / phosphorus / silicon composite material.
[0029] Step S2: Dissolve 100g of furfural resin in 1500g of xylene organic solvent, add 10g of silver / phosphorus / silicon composite material and ultrasonically disperse (ultrasonic frequency 25KHz, dispersion speed 5000r / min, dispersion time 60min), and obtain precursor material by spray drying (inlet air temperature 200℃, flow rate 60mL / min, outlet air temperature 80℃). Transfer the precursor material to a tube furnace and carbonize it at 1000℃ for 1h under an argon inert atmosphere to obtain amorphous carbon-coated silver / phosphorus / silicon composite material.
[0030] Step S3: 100g of amorphous carbon-coated silver / phosphorus / silicon composite material was mixed with 10g of polyvinylidene fluoride and pressed into a block structure as the working electrode, and a saturated calomel electrode was used as the counter electrode. At the same time, 0.1mol / L lithium difluorodioxarate phosphate in ethylene carbonate was prepared. Lithium salt was deposited on the surface of the working electrode by constant voltage method (voltage 2V) for 120min. The electrode was washed 5 times with 1mol / L hydrochloric acid, vacuum dried at 80℃ for 24h, and carbonized at 1000℃ for 1h to obtain the phosphorus-silver-silicon co-doped hard carbon composite material.
[0031] Comparative Example 1:
[0032] A method for preparing a composite material includes the following steps:
[0033] Unlike Example 1, no red phosphorus or silver powder was added; otherwise, it was the same as Example 1.
[0034] Comparative Example 2:
[0035] A method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material includes the following steps:
[0036] The amorphous carbon-coated silver / phosphorus / silicon composite material prepared in step S2 of Example 1 was transferred to a tube furnace and carbonized at 800°C for 3 hours to obtain a phosphorus-silver-silicon co-doped hard carbon composite material.
[0037] Experimental example:
[0038] Performance tests were conducted on the materials prepared in Examples 1-3 and Comparative Examples 1-2 above.
[0039] (1) SEM test
[0040] The phosphorus-silver-silicon co-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. By Figure 1 As can be seen from the results, the hard carbon composite material prepared in Example 1 exhibits a spherical structure with a uniform size distribution and a particle size between 1 and 5 µm.
[0041] (2) Physical and chemical properties and button cell testing
[0042] The phosphorus-silver-silicon co-doped hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested for particle size, tap density, specific surface area, interlayer spacing, trace element content (phosphorus-silver-silicon), powder resistivity, and powder OI value. Trace element content was measured by EDS, interlayer spacing by XRD, and other tests were performed according to the methods in the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". The test results are shown in Table 1.
[0043] Table 1
[0044]
[0045] The phosphorus-silver-silver co-doped hard carbon composite materials from Examples 1-3 and Comparative Examples 1-2 were used as negative electrode materials for lithium-ion batteries to assemble coin cells. The specific preparation method for the negative electrode material was as follows: a binder, conductive agent, and solvent were added to the composite material, stirred to form a slurry, coated onto copper foil, and then dried and rolled. The binder used was LA132, the conductive agent was SP, and the solvent was double-distilled water. The negative electrode sheet was prepared according to the ratio of composite material: SP:LA132:double-distilled water = 90g:3g:7g:220mL. A lithium metal sheet was used as the counter electrode. The electrolyte was LiPF6 / EC+DEC, where LiPF6 was the electrolyte, and a 1:1 volume ratio mixture of EC and DEC was used as the solvent, with an electrolyte concentration of 1.3 mol / L. A polyethylene (PE) membrane was used as the separator. The coin cells were assembled in an argon-filled glove box. Electrochemical performance was performed using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.00V to 2.0V, and the charge / discharge rate was 0.1C. The initial discharge capacity and initial efficiency of the coin cells were tested, along with rate performance (2C, 0.1C) and cycle performance (0.2C / 0.2C, 200 cycles). The test results are shown in Table 2.
[0046] Table 2
[0047]
[0048] As can be seen from Tables 1 and 2, the materials prepared in the embodiments of the present invention have high specific capacity and first-pass efficiency. This is because the filling of phosphorus, silver and silicon in the hard carbon material increases the electronic conductivity and improves the rate performance. At the same time, silver material has the characteristic of high tap density, which improves the tap density of the material. Silver also has a catalytic effect, which can generate hard carbon material with high interlayer spacing during the carbonization process of the material and improve the rate performance. Silicon has high specific capacity, which improves the energy density.
[0049] (3) Soft-pack battery test:
[0050] The phosphorus-silver-silicon co-doped hard carbon composite materials from Examples 1-3 and Comparative Examples 1-2 were slurried and coated to prepare negative electrode sheets, using ternary materials (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 A 2Ah pouch cell was prepared using O2 as the positive electrode, LiPF6 (solvent EC+DEC, volume ratio 1:1, electrolyte concentration 1.3mol / L) as the electrolyte, and Celgard 2400 membrane as the separator.
[0051] The rate performance of the pouch battery was tested under a charge / discharge voltage range of 2.5–4.2V and a temperature of 25±3.0℃. Charging was performed at 1.0C, 3.0C, 5.0C, and 10.0C, and discharging was performed at 1.0C. The results are shown in Table 3.
[0052] Table 3
[0053]
[0054] As shown in Table 3, the rate charging performance of the soft-pack batteries prepared by the materials in Examples 1-3 is significantly better than that of Comparative Examples 1-2, that is, the charging time is shorter. The reason for this is that lithium ions need to migrate during the battery charging process, and the hard carbon anode material in the examples is doped with silver with high electronic conductivity to reduce impedance. At the same time, the large interlayer spacing of the materials in the examples improves the rate performance and constant current ratio.
[0055] (4) Cyclic performance test:
[0056] The cycle performance test conditions were: charge / discharge current 3C / 3C, voltage range 2.5-4.2V, and 500 cycles. The test results are shown in Table 4.
[0057] Table 4
[0058]
[0059] As shown in Table 4, the lithium-ion batteries prepared using the composite materials obtained in Examples 1-3 exhibit significantly better cycle performance than the comparative examples. This is because the composite materials are doped with silver, which fills the pores of the hard carbon, reducing side reactions between the material and the electrolyte. This improves the initial efficiency and compatibility with the electrolyte, thus enhancing cycle performance. Simultaneously, the low electronic impedance of the doped silver further reduces side reactions during charge and discharge, further improving cycle performance. Furthermore, the presence of lithium doping provides sufficient lithium ions to enhance cycle performance.
[0060] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.
Claims
1. A method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material, comprising the following steps: Step S1: Add micron-sized silicon to a high-energy ball mill and grind for 12-72 hours according to the mass ratio of silver powder: red phosphorus: nano silicon = 1-5: 10: 1-5 to obtain nano silicon with a particle size of 100-200nm. After obtaining nano silicon, continue to add red phosphorus and silver powder to the ball mill and grind for 12-72 hours. Then, vacuum dry at 80℃ for 24 hours to obtain a silver / phosphorus / silicon composite material. Step S2: Dissolve the resin in an organic solvent at a mass ratio of resin: organic solvent: silver / phosphorus / silicon composite material = 100:500-1500:1-10, then add the silver / phosphorus / silicon composite material and perform ultrasonic dispersion at a frequency of 25 kHz, a dispersion speed of 5000 r / min, and a dispersion time of 60 min. Then, spray dry the material at an inlet air temperature of 200℃, a flow rate of 60 mL / min, and an outlet air temperature of 80℃ to obtain the precursor material. Transfer the precursor material to a tube furnace and carbonize it at 600-1000℃ for 1-6 h under an inert atmosphere to obtain an amorphous carbon-coated silver / phosphorus / silicon composite material. Step S3: According to the mass ratio of amorphous carbon-coated silver / phosphorus / silicon composite material: binder = 100: 1-10, the amorphous carbon-coated silver / phosphorus / silicon composite material and binder are mixed and pressed into a block structure as the working electrode, and a saturated calomel electrode is used as the counter electrode. At the same time, 0.1 mol / L lithium difluorodioxarate phosphate in ethylene carbonate is prepared. Lithium salt is deposited on the surface of the working electrode by electrochemical deposition. After the deposition time is 10-120 min, it is washed 1-5 times with 1 mol / L hydrochloric acid, vacuum dried at 80℃ for 24 h, and carbonized at 700-1000℃ for 1-6 h to obtain a phosphorus-silver-silicon co-doped hard carbon composite material.
2. The method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material as described in claim 1, wherein: The resin mentioned in step S2 is one of phenolic resin, furfural resin, or epoxy resin; the organic solvent is one of chloroform, toluene, acetone, or xylene.
3. The method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material as described in claim 1, wherein: The adhesive mentioned in step S2 is one of polyvinyl alcohol, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, or sodium carboxymethyl cellulose.
4. The method for preparing a phosphorus-silver-silicon co-doped hard carbon composite material as described in claim 1, wherein: The electrochemical deposition method described in step S3 is one of cyclic voltammetry, constant voltage method, constant current method, or pulse method; the parameters for cyclic voltammetry are -2V to 2V and 0.5-5mV / s; the parameters for constant voltage method are 2V; and the parameters for constant current method are 1-10mA / cm. 2 .