Phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon negative electrode material and preparation method thereof

Abstract

The invention provides a phosphorus, nitrogen and sulfur co-doped porous carbon coated hollow silicon negative electrode material and a preparation method thereof, and the preparation method comprises the following steps: coating a metal organic framework material ZIF-67 with SiO2 in situ to obtain SiO2 (at) ZIF-67; coating SiO2 (at) ZIF-67 with a phosphorus, nitrogen and sulfur co-doped polymer PZS in situ, so as to obtain SiO2 (at) ZIF-67 (at) PZS; and carrying out magnesiothermic reduction on SiO2 (at) ZIF-67 (at) PZS, and then carrying out high-temperature carbonization to obtain the phosphorus-nitrogen-sulfur co-doped porous carbon coated hollow silicon negative electrode material. Through a three-in-one strategy of template induction of the metal organic framework, phosphorus-nitrogen-sulfur heteroatom synergistic doping and carbon shell construction, the technical defects that a traditional silicon negative electrode material is short in cycle life, poor in rate capability, complex in preparation and the like are overcome.

Description

Technical Field

[0001] This invention belongs to the field of anode material technology, and particularly relates to a phosphorus, nitrogen and sulfur co-doped porous carbon-coated hollow silicon anode material and its preparation method. Background Technology

[0002] With the rapid development of electric vehicles and portable electronic devices, the market has placed higher demands on the energy density and cycle life of lithium-ion batteries. Silicon, as a negative electrode material for lithium-ion batteries, possesses an extremely high theoretical specific capacity (approximately 4200 mAh / g), but it suffers from severe volume expansion (>300%) during charge and discharge, leading to electrode structure damage, decreased conductivity, and rapid capacity decay. Furthermore, silicon itself has poor conductivity and insufficient interfacial stability. Therefore, effectively controlling the microstructure of silicon to improve its cycle stability and electrochemical performance has become a research hotspot.

[0003] Current mainstream methods include carbon coating, hollow core-shell structures, porous structure design, and heteroatom doping. However, these technologies are often used in a fragmented manner, failing to achieve integrated optimization of structure and function, and suffer from problems such as complex processes and high costs. Therefore, developing a silicon-based composite anode material that is easy to prepare, structurally sound, and exhibits excellent performance is of great significance. Summary of the Invention

[0004] Based on the above-mentioned technical problems, the present invention provides a phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material and its preparation method. Through a three-in-one strategy of template induction by metal-organic framework, synergistic doping of phosphorus, nitrogen, and sulfur heteroatoms, and carbon shell construction, the technical defects of traditional silicon anode materials, such as short cycle life, poor rate performance, and complex preparation, are solved.

[0005] The present invention proposes a method for preparing a phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material, comprising the following steps: S1. SiO2 is in situ coated with metal-organic framework material ZIF-67 to obtain SiO2@ZIF-67; S2. In-situ coating of SiO2@ZIF-67 with phosphorus, nitrogen and sulfur co-doped polymer PZS yields SiO2@ZIF-67@PZS. S3. After magnesium thermoreduction of SiO2@ZIF-67@PZS, high-temperature carbonization is carried out to obtain the phosphorus, nitrogen and sulfur co-doped porous carbon-coated hollow silicon anode material.

[0006] Preferably, in step S1, SiO2 is reacted in situ with 2-methylimidazole and cobalt salt to achieve in situ coating of ZIF-67 with SiO2. Preferably, the molar ratio of SiO2 to 2-methylimidazole and cobalt salt is 1:0.2-0.4:2-4; Preferably, the cobalt salt is at least one of cobalt nitrate or cobalt acetate; Preferably, the in-situ reaction temperature is 20-30℃ and the time is 6-24h.

[0007] In this invention, a metal-organic framework (MOF) material shell is constructed in situ on the surface of silica particles to form a porous structural template and a carbon source precursor. The MOF is preferably ZIF-67, a structurally stable material composed of a cobalt transition metal center and an imidazole body. Compared with the tetrahedral structure of other MOFs, the dodecahedral hollow framework structure of ZIF-67 has physicochemical advantages due to its topological polyhedral structure, such as a higher coordination number, higher chemical activity, more lone pairs of electrons, higher bonding degree, and higher lithium-ion absorption rate. Furthermore, these characteristics help improve the electrochemical performance of its derived polyhedral carbon, greatly alleviating the problem of large volume expansion / contraction of silicon-based materials during charging / discharging.

[0008] Preferably, in step S2, SiO2@ZIF-67, hexachlorocyclotriphosphazene, and bisphenol S are polymerized under acid-binding agent conditions to achieve in-situ coating of PZS with SiO2@ZIF-67. Preferably, the mass ratio of SiO2 to hexachlorocyclotriphosphazene and bisphenol S is 1:0.4-0.6:1.0-1.5; Preferably, the acid-binding agent is at least one of triethylamine or pyridine; Preferably, the in-situ polymerization reaction temperature is 20-30℃ and the time is 6-12h.

[0009] In this invention, a three-dimensional cross-linked phosphorus-nitrogen-sulfur co-doped polymer (PZS) is formed by in-situ polycondensation of hexachlorocyclotriphosphazene (HCCP) and bisphenol S (BPS). On the one hand, by introducing a three-dimensional cross-linked polymer precursor, a highly doped, high-strength porous carbon layer is constructed. On the other hand, after carbonization, a dense, mechanically excellent, triple-doped carbon shell can be generated, possessing both buffering and conductive functions: the doping of N and P atoms disrupts the sp... 2 The inertness of the hybrid carbon network attracts more electrons and increases the positive charge density of adjacent carbon atoms in N and P, while improving the conductivity and hydrophilicity of the carbon network; the introduction of S polarizes the electron pairs and improves electrochemical performance; therefore, multi-element co-doping can produce a synergistic effect, further improving battery performance, such as superior cycle stability and high reversible capacity, as well as good rate performance.

[0010] Preferably, in step S3, the magnesium thermal reduction temperature is 650-750℃ and the time is 1-3h.

[0011] Preferably, in step S3, the high-temperature carbonization temperature is 700-900℃ and the time is 2-4h.

[0012] Preferably, in step S1, before coating the metal-organic framework material ZIF-67 with SiO2 in situ, the method further includes adsorbing polyvinylpyrrolidone (PVP) onto the surface of SiO2 to obtain SiO2@PVP. Preferably, the mass ratio of SiO2 to polyvinylpyrrolidone is 1:0.5-1.5.

[0013] In this invention, since the surface of SiO2 particles is relatively hydrophobic, direct in-situ growth of ZIF-67 results in low nucleation density and uneven coating. Therefore, the surface of SiO2 particles is pretreated before ZIF growth by introducing the interfacial bridging agent PVP to improve hydrophilicity and MOF adhesion, thereby achieving high-quality core-shell structure construction.

[0014] Preferably, the SiO2 is obtained by hydrolyzing a silicon dioxide precursor under ammonia conditions; Preferably, the silica precursor comprises an alkyl silicate, and is preferably at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate or butyl orthosilicate.

[0015] Preferably, the silica precursor comprises an aminosilane coupling agent, preferably at least one of 3-aminopropyltriethoxysilane or 3-(2-aminoethylamino)propyltrimethoxysilane; Preferably, the mass ratio of the alkyl silicate ester to the aminosilane coupling agent is 1:0.1-0.3.

[0016] In this invention, when obtaining SiO2 particles through alkaline hydrolysis, an aminosilane coupling agent is simultaneously added for hydrolysis, resulting in the grafting of amino groups onto the surface of the obtained SiO2 particles. These amino groups can react with the carbonyl groups of PVP during subsequent adsorption to form imines. This not only helps to improve the adsorption efficiency of PVP on the surface of SiO2 particles, but also facilitates the adsorption of cobalt ions during the subsequent construction of ZIF-67, thus promoting the in-situ generation of ZIF-67 on the surface of SiO2 particles and improving the electrochemical performance of the obtained negative electrode material.

[0017] This invention also proposes a phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material, which is prepared by the above-mentioned preparation method.

[0018] The present invention also proposes a lithium-ion battery comprising the above-mentioned phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material.

[0019] Compared with the prior art, the present invention has the following technical effects: In this invention, a ZIF-67 core-shell template structure is constructed in situ on the SiO2 surface as a porous template and carbon precursor to form a composite core-shell structure, guiding the formation of controllable pores and an interface framework. Furthermore, a polymer containing N / P / S heteroatoms, generated by the reaction of hexachlorocyclotriphosphazene (HCCP) and bisphenol S (BPS), is introduced as a functional carbon precursor. During high-temperature carbonization, a uniformly coated multi-doped porous carbon layer is formed, significantly improving the electrode structure integrity, conductivity, and interface stability. Finally, the SiO2→Si conversion and structural cavity release are achieved by combining the magnesothermic reduction method, ultimately obtaining a composite anode material with high capacity, high rate capability, and long cycle performance. This material possesses technical advantages such as simple process, strong material versatility, and suitability for large-scale production, and has broad prospects for industrial application. Attached Figure Description

[0020] Figure 1 The image shows the SEM image of the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material described in Example 1. Detailed Implementation

[0021] The present invention will now be described in detail through specific embodiments. However, these embodiments are clearly provided for illustrative purposes and are not intended to limit the scope of the present invention.

[0022] Example 1 A phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate was dissolved in anhydrous ethanol, and then a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol in a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres (particle size of about 100 nm). (2) 100 mg of the above SiO2 nanospheres were dispersed in 40 mL of methanol and sonicated for 15 min. Then, solution A and solution B were slowly added. Solution A was obtained by dissolving 145 mg of Co(NO3)2·6H2O in 20 mL of methanol, and solution B was obtained by dissolving 328 mg of 2-methylimidazole in 20 mL of methanol. After standing at room temperature for 12 h, the mixture was centrifuged, washed, and dried to obtain SiO2@ZIF-67. (3) The above SiO2@ZIF-67 was dispersed in 160 mL of methanol, and solution C was slowly added. Solution C was obtained by dissolving 482 mg of bisphenol S (BPS) and 272 mg of hexachlorocyclotriphosphazene (HCCP) in 40 mL of methanol. After stirring for 10 min, 0.4 mL of triethylamine (TEA) was added dropwise. The resulting reaction system was stirred at room temperature for 8 h. BPS and HCCP were polymerized in situ and coated on the surface of SiO2@ZIF-67. After centrifugation, washing and drying, SiO2@ZIF-67@PZS was obtained. (4) The SiO2@ZIF-67@PZS and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. Under an argon atmosphere, the temperature was increased to 700℃ at 5℃ / min and held for 1h. The resulting product was dissolved in 1M hydrochloric acid for 2h, centrifuged, washed, and dried. Then, under an argon atmosphere, the temperature was increased to 800℃ and carbonized for 3h to promote the complete carbonization of the three-dimensional cross-linked polymer (PZS) and the residual carbon source of ZIF-67, forming a porous carbon shell structure rich in N, P, and S, while fixing the Si core. Thus, the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material was obtained. Its microstructure is as shown in the figure. Figure 1 As shown.

[0023] Example 2 A phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate was dissolved in anhydrous ethanol, and then a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol in a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres (particle size of about 100 nm). (2) 100 mg of the above SiO2 nanospheres were dispersed in 100 mL of anhydrous ethanol, 100 mg of PVP was added, and the mixture was ultrasonically dispersed for 30 min until it was uniformly dispersed. After magnetic stirring at room temperature for 2 h, PVP was uniformly adsorbed on the surface of SiO2. After centrifugation, washing and drying, SiO2@PVP was obtained. (3) The above SiO2@PVP was redispersed in 40 mL of methanol, sonicated for 15 min, and then solution A and solution B were slowly added. Solution A was obtained by dissolving 145 mg of Co(NO3)2·6H2O in 20 mL of methanol, and solution B was obtained by dissolving 328 mg of 2-methylimidazole in 20 mL of methanol. After standing at room temperature for 12 h, the mixture was centrifuged, washed, and dried to obtain SiO2@PVP@ZIF-67. (4) The above SiO2@PVP@ZIF-67 was dispersed in 160 mL of methanol, and solution C was slowly added. Solution C was obtained by dissolving 482 mg of bisphenol S (BPS) and 272 mg of hexachlorocyclotriphosphazene (HCCP) in 40 mL of methanol. After stirring for 10 min, 0.4 mL of triethylamine (TEA) was added dropwise. The resulting reaction system was stirred at room temperature for 8 h. BPS and HCCP were polymerized in situ and coated on the surface of SiO2@PVP@ZIF-67. After centrifugation, washing and drying, SiO2@PVP@ZIF-67@PZS was obtained. (5) The SiO2@PVP@ZIF-67@PZS and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. The temperature was raised to 700°C at 5°C / min under an argon atmosphere and kept at that temperature for 1 hour. The resulting product was dissolved in 1M hydrochloric acid for 2 hours, centrifuged, washed, and dried. Then, it was carbonized at 800°C under an argon atmosphere for 3 hours to promote the complete carbonization of the three-dimensional cross-linked polymer (PZS) and the residual carbon source of ZIF-67, forming a porous carbon shell structure rich in N, P, and S, while fixing the Si core, thus obtaining the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material.

[0024] Example 3 A phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate and 3-aminopropyltriethoxysilane were dissolved in anhydrous ethanol at a mass ratio of 1:0.2. Then, a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol at a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres. (2) 100 mg of the above SiO2 nanospheres were dispersed in 100 mL of anhydrous ethanol, 100 mg of PVP was added, and the mixture was ultrasonically dispersed for 30 min until it was uniformly dispersed. The mixture was heated to 80 °C and magnetically stirred for 2 h. After centrifugation, washing and drying, SiO2@PVP was obtained. (3) The above SiO2@PVP was redispersed in 40 mL of methanol, sonicated for 15 min, and then solution A and solution B were slowly added. Solution A was obtained by dissolving 145 mg of Co(NO3)2·6H2O in 20 mL of methanol, and solution B was obtained by dissolving 328 mg of 2-methylimidazole in 20 mL of methanol. After standing at room temperature for 12 h, the mixture was centrifuged, washed, and dried to obtain SiO2@PVP@ZIF-67. (4) The above SiO2@PVP@ZIF-67 was dispersed in 160 mL of methanol, and solution C was slowly added. Solution C was obtained by dissolving 482 mg of bisphenol S (BPS) and 272 mg of hexachlorocyclotriphosphazene (HCCP) in 40 mL of methanol. After stirring for 10 min, 0.4 mL of triethylamine (TEA) was added dropwise. The resulting reaction system was stirred at room temperature for 8 h. BPS and HCCP were polymerized in situ and coated on the surface of SiO2@PVP@ZIF-67. After centrifugation, washing and drying, SiO2@PVP@ZIF-67@PZS was obtained. (5) The SiO2@PVP@ZIF-67@PZS and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. The temperature was raised to 700°C at 5°C / min under an argon atmosphere and kept at that temperature for 1 hour. The resulting product was dissolved in 1M hydrochloric acid for 2 hours, centrifuged, washed, and dried. Then, it was carbonized at 800°C under an argon atmosphere for 3 hours to promote the complete carbonization of the three-dimensional cross-linked polymer (PZS) and the residual carbon source of ZIF-67, forming a porous carbon shell structure rich in N, P, and S, while fixing the Si core, thus obtaining the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material.

[0025] Comparative Example 1 A phosphorus, nitrogen, and sulfur co-doped carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate was dissolved in anhydrous ethanol, and then a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol in a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres (particle size of about 100 nm). (2) 100 mg of the above SiO2 nanospheres were dispersed in 160 mL of methanol, and solution C was slowly added. Solution C was obtained by dissolving 482 mg of bisphenol S (BPS) and 272 mg of hexachlorocyclotriphosphazene (HCCP) in 40 mL of methanol. After stirring for 10 min, 0.4 mL of triethylamine (TEA) was added dropwise. The resulting reaction system was stirred at room temperature for 8 h. BPS and HCCP were polymerized in situ and coated on the surface of SiO2@ZIF-67. After centrifugation, washing and drying, SiO2@PZS was obtained. (3) The SiO2@PZS and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. The temperature was raised to 700°C at 5°C / min under an argon atmosphere and kept at the temperature for 1 hour. The resulting product was dissolved in 1M hydrochloric acid for 2 hours, centrifuged, washed, and dried. Then, it was heated to 800°C under an argon atmosphere and carbonized for 3 hours to promote the complete carbonization of the three-dimensional cross-linked polymer (PZS) and form a carbon shell structure rich in N, P, and S. At the same time, the Si core was fixed, thus obtaining the phosphorus, nitrogen, and sulfur co-doped carbon-coated hollow silicon anode material.

[0026] Comparative Example 2 A porous carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate was dissolved in anhydrous ethanol, and then a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol in a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres (particle size of about 100 nm). (2) 100 mg of the above SiO2 nanospheres were dispersed in 40 mL of methanol and sonicated for 15 min. Then, solution A and solution B were slowly added. Solution A was obtained by dissolving 145 mg of Co(NO3)2·6H2O in 20 mL of methanol, and solution B was obtained by dissolving 328 mg of 2-methylimidazole in 20 mL of methanol. After standing at room temperature for 12 h, the mixture was centrifuged, washed, and dried to obtain SiO2@ZIF-67. (3) The SiO2@ZIF-67 and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. The temperature was raised to 700°C at 5°C / min under an argon atmosphere and held for 1 hour. The resulting product was dissolved in 1M hydrochloric acid for 2 hours, centrifuged, washed, and dried. Then, it was heated to 800°C under an argon atmosphere and carbonized for 3 hours to promote the complete carbonization of the residual carbon source of ZIF-67, forming a porous carbon shell structure and fixing the Si core, thus obtaining the porous carbon-coated hollow silicon anode material.

[0027] Comparative Example 3 A phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate was dissolved in anhydrous ethanol, and then a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol in a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres (particle size of about 100 nm). (2) 100 mg of the above SiO2 nanospheres were dispersed in 40 mL of methanol and sonicated for 15 min. Then, solution A and solution B were slowly added. Solution A was obtained by dissolving 145 mg of Co(NO3)2·6H2O in 20 mL of methanol, and solution B was obtained by dissolving 328 mg of 2-methylimidazole in 20 mL of methanol. After standing at room temperature for 12 h, the mixture was centrifuged, washed, and dried to obtain SiO2@ZIF-67. (3) The above SiO2@ZIF-67 was dispersed in 160 mL of methanol, and solution C was slowly added. Solution C was obtained by dissolving 482 mg of bisphenol S (BPS) and 272 mg of hexachlorocyclotriphosphazene (HCCP) in 40 mL of methanol. After stirring for 10 min, it was stirred at room temperature for 8 h, centrifuged, washed, and dried to obtain SiO2@ZIF-67@BPS-HCCP. (4) The SiO2@ZIF-67@BPS-HCCP and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. The temperature was raised to 700°C at 5°C / min under an argon atmosphere and held for 1 hour. The resulting product was dissolved in 1M hydrochloric acid for 2 hours, centrifuged, washed, and dried. Then, it was carbonized at 800°C under an argon atmosphere for 3 hours to promote the complete carbonization of BPS-HCCP and the residual carbon source of ZIF-67, forming a porous carbon shell structure rich in N, P, and S, while fixing the Si core, thus obtaining the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material.

[0028] Comparative Example 4 A phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material is prepared by the following method: (1) Tetraethyl orthosilicate and n-propyltriethoxysilane were dissolved in anhydrous ethanol at a mass ratio of 1:0.2. Then, a mixed solvent consisting of concentrated ammonia (25wt%), deionized water and anhydrous ethanol at a volume ratio of 1:2:20 was added. After stirring at room temperature for 6 hours, the mixture was centrifuged, washed and dried to obtain SiO2 nanospheres. (2) 100 mg of the above SiO2 nanospheres were dispersed in 100 mL of anhydrous ethanol, 100 mg of PVP was added, and the mixture was ultrasonically dispersed for 30 min until it was uniformly dispersed. The mixture was heated to 80 °C and magnetically stirred for 2 h. After centrifugation, washing and drying, SiO2@PVP was obtained. (3) The above SiO2@PVP was redispersed in 40 mL of methanol, sonicated for 15 min, and then solution A and solution B were slowly added. Solution A was obtained by dissolving 145 mg of Co(NO3)2·6H2O in 20 mL of methanol, and solution B was obtained by dissolving 328 mg of 2-methylimidazole in 20 mL of methanol. After standing at room temperature for 12 h, the mixture was centrifuged, washed, and dried to obtain SiO2@PVP@ZIF-67. (4) The above SiO2@PVP@ZIF-67 was dispersed in 160 mL of methanol, and solution C was slowly added. Solution C was obtained by dissolving 482 mg of bisphenol S (BPS) and 272 mg of hexachlorocyclotriphosphazene (HCCP) in 40 mL of methanol. After stirring for 10 min, 0.4 mL of triethylamine (TEA) was added dropwise. The resulting reaction system was stirred at room temperature for 8 h. BPS and HCCP were polymerized in situ and coated on the surface of SiO2@PVP@ZIF-67. After centrifugation, washing and drying, SiO2@PVP@ZIF-67@PZS was obtained. (5) The SiO2@PVP@ZIF-67@PZS and magnesium powder were mixed at a mass ratio of 2:1, ground evenly, and placed in a sealed quartz tube furnace. The temperature was raised to 700°C at 5°C / min under an argon atmosphere and kept at that temperature for 1 hour. The resulting product was dissolved in 1M hydrochloric acid for 2 hours, centrifuged, washed, and dried. Then, it was carbonized at 800°C under an argon atmosphere for 3 hours to promote the complete carbonization of the three-dimensional cross-linked polymer (PZS) and the residual carbon source of ZIF-67, forming a porous carbon shell structure rich in N, P, and S, while fixing the Si core, thus obtaining the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material.

[0029] The negative electrode materials obtained in the examples and comparative examples were mixed with conductive agent (SP), binder (CMC), and binder (SBR) in water at a weight ratio of 95:1:2:2 to prepare a negative electrode slurry. The slurry was coated on the surface of copper foil and dried in a vacuum drying oven at 130°C for 6 hours. After stamping, a negative electrode sheet was obtained. The obtained negative electrode sheet was then assembled into a simulated battery in a Braun glove box under argon protection. The electrolyte was 1 mol / L LiPF6, the solvent was EC:DMC:EMC=1:1:1 (v / v / v), the lithium metal sheet was used as the counter electrode, and the American Cellgard 2400 was used as the separator.

[0030] The simulated batteries were tested for electrochemical performance using an Arbin BT2000 battery tester. The charge / discharge voltage range was 0.005-1.5V, and the charge / discharge rate was 0.1C. For the 500-cycle capacity retention test, the charge / discharge rate was 1C. For the rate performance test, the charging current was 0.1C and the discharging current was 3C. The test results are shown in Table 1 below.

[0031] Table 1. Performance comparison of the negative electrode materials described in the embodiments and comparative examples.

[0032] As shown in Table 1 above, Example 1, which is simultaneously induced by metal-organic framework templates and co-doped with phosphorus, nitrogen, and sulfur heteroatoms, exhibits significantly better cycle stability, high reversible capacity, and rate performance than Comparative Example 1, which is only co-doped with phosphorus, nitrogen, and sulfur heteroatoms, Comparative Example 2, which is only induced by metal-organic framework templates, and Comparative Example 3, which is co-doped with nitrogen and sulfur heteroatoms but not in a three-dimensional cross-linked phosphorus, nitrogen, and sulfur co-doped polymer manner. Furthermore, Example 2, which is pre-treated with PVP surface, and Example 3, which is pre-treated with an aminosilane coupling agent / PVP system surface, exhibit better anode material performance than Example 1. However, Comparative Example 3, which is pre-treated with a silane coupling agent / PVP system surface, has worse performance than Example 2, which is pre-treated with PVP surface.

[0033] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon negative electrode material, characterized in that, Comprising the following steps: S1, in-situ coating SiO2 on metal organic framework material ZIF-67 to obtain SiO2@ZIF-67; S2, in-situ coating SiO2@ZIF-67 with phosphorus-nitrogen-sulfur co-doped polymer PZS to obtain SiO2@ZIF-67@PZS; S3, after magnesium hot reduction of SiO2@ZIF-67@PZS, high-temperature carbonization, the phosphorus-nitrogen-sulfur co-doped porous carbon coated hollow silicon negative electrode material is obtained.

2. The method for preparing the phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon negative electrode material according to claim 1, characterized in that, In step S1, in-situ reaction of SiO2, 2-methyl imidazole and cobalt salt is carried out, that is, SiO2 is in-situ coated on ZIF-67; Preferably, the molar ratio of SiO2, 2-methyl imidazole and cobalt salt is 1:0.2-0.4:2-4; Preferably, the cobalt salt is at least one of cobalt nitrate or cobalt acetate; Preferably, the in-situ reaction temperature is 20-30℃, and the time is 6-24h.

3. The method for preparing the phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon negative electrode material according to claim 1 or 2, characterized in that, In step S2, polymerization reaction of SiO2@ZIF-67, hexachlorocyclotriphosphazene and bisphenol S is carried out under the condition of an acid binding agent, that is, SiO2@ZIF-67 is in-situ coated with PZS; Preferably, the mass ratio of SiO2, hexachlorocyclotriphosphazene and bisphenol S is 1:0.4-0.6:1.0-1.5; Preferably, the acid binding agent is at least one of triethylamine or pyridine; Preferably, the polymerization reaction temperature is 20-30℃, and the time is 6-12h.

4. The method for preparing the phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon negative electrode material according to any one of claims 1-3, characterized in that, In step S3, the magnesium hot reduction temperature is 650-750℃, and the time is 1-3h.

5. The method for preparing the phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon anode material according to any one of claims 1-4, characterized in that, In step S3, the high-temperature carbonization temperature is 700-900℃, and the time is 2-4h.

6. The method for preparing the phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon anode material according to any one of claims 1-5, characterized in that, In step S1, before in-situ coating SiO2 on metal organic framework material ZIF-67, SiO2 surface adsorption of polyvinylpyrrolidone PVP is further included to obtain SiO2@PVP; Preferably, the mass ratio of SiO2 and polyvinylpyrrolidone is 1:0.5-1.

5.

7. The method for preparing the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material according to claim 6, characterized in that, The SiO2 is obtained by hydrolysis reaction of a silicon dioxide precursor under the condition of ammonia water; Preferably, the silicon dioxide precursor includes at least one of alkyl silicate, preferably methyl silicate, ethyl silicate, propyl silicate or butyl silicate.

8. The method for preparing the phosphorus, nitrogen, and sulfur co-doped porous carbon-coated hollow silicon anode material according to claim 7, characterized in that, The silicon dioxide precursor includes at least one of amino silane coupling agent, preferably 3-aminopropyl triethoxysilane or 3-(2-aminoethylamino) propyl trimethoxysilane; Preferably, the mass ratio of alkyl silicate and amino silane coupling agent is 1:0.1-0.

3.

9. A phosphorus-nitrogen-sulfur co-doped porous carbon-coated hollow silicon anode material, characterized in that, It is prepared by the preparation method of any one of claims 1-8.

10. A lithium-ion battery, characterized by, It comprises the phosphorus-nitrogen-sulfur co-doped porous carbon coated hollow silicon negative electrode material of claim 9.

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