Metal-doped silicon carbon composites and their manufacturing methods and applications

Abstract

A metal-doped silicon carbon composite material, its manufacturing method and application, has a core-shell structure consisting of a core and an outer shell, the core comprising metal- and / or heteroatom-doped porous carbon and nanosilicon, the outer shell comprising lithium-doped amorphous carbon, and the weight ratio of the outer shell to the core-shell structure being 10 wt% or less.

Description

[Technical Field]

[0001] This application claims priority to Chinese Patent Application No. 202310773017X, entitled "Metal-doped silicon carbon composite material and its manufacturing method and application," filed with the Patent Office of the State Intellectual Property Administration of the People's Republic of China on June 27, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the field of lithium ion battery material manufacturing, specifically to a metal-doped silicon carbon composite material, and further to a manufacturing method of the metal-doped silicon carbon composite material and its application. [Background technology]

[0003] Silicon carbon composites have been applied to high-energy-density lithium-ion batteries due to their advantages, such as high energy density and wide availability of materials. However, they suffer from drawbacks, such as large expansion when fully charged and high impedance, which pose risks during use, such as temperature variations during high-temperature storage and rapid decline in battery capacity due to large expansion. Currently, the main methods for reducing expansion include nanosizing the material, adopting a porous structure, and using nanosilicon materials with small silicon crystal grains, which reduce material expansion during charging and discharging. The use of nanosilicon materials with small silicon crystal grains (silicon crystal size <2nm) significantly reduces silicon expansion because their size is much smaller than the silicon crystal grain size in silicon-oxygen materials (approximately 6nm).

[0004] However, the applicant has found that the nanosilicon currently produced by the silane decomposition method has low silicon crystal grains and is deposited in porous carbon particles, but the porous carbon particles themselves have differences in electronic conductivity, which causes deviations in the rate performance of the material.Furthermore, although the porous structure of the porous carbon itself can reduce the expansion of silicon during the charge and discharge process, the differences in electronic conductivity of the material itself cause a decrease in fast charging performance.

[0005] Therefore, the applicant would like to seek a technical solution to improve the above technical problems. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a metal-doped silicon carbon composite material with excellent power performance and initial efficiency, as well as its manufacturing method and application, and the manufacturing method provided in this application is simple and efficient, economical and practical, and easy to be industrialized on a large scale.

[0007] The technical solutions used in the present invention are as follows:

[0008] A metal-doped silicon carbon composite material has a core-shell structure consisting of a core and an outer shell, wherein the core comprises metal- and / or heteroatom-doped porous carbon and nanosilicon, and the outer shell comprises lithium-doped amorphous carbon, and the weight ratio of the outer shell to the core-shell structure is 10 wt % or less.

[0009] Preferably, the weight ratio of the outer shell to the core-shell structure is 1 to 5% by weight.

[0010] Preferably, the metal in the core is silver and / or copper, and the heteroatom is one or more of nitrogen, sulfur, and phosphorus.

[0011] Preferably, in the core, the mass ratio of the metal, porous carbon and nanosilicon is in the range of 1-5:40-60:40-60, and / or the mass ratio of the heteroatom, porous carbon and nanosilicon is in the range of 1-5:40-60:40-60.

[0012] Preferably, the method for producing such a metal-doped silicon carbon composite material comprises at least the following operational steps: Step S1) of uniformly mixing a carbon source, a heteroatom compound, and / or an organometallic compound, and then carbonizing the mixture at a temperature of 500 to 800°C for at least 1 hour to obtain doped porous carbon; Step S2) of transferring the doped porous carbon obtained in step S1) to a first reaction vessel, passing a mixed gas of chlorosilane and an inert gas through the first reaction vessel, and passing the mixed gas through the first reaction vessel at a temperature of 300 to 500°C for at least 1 hour to obtain a silicon carbon precursor material; and step S3) of transferring the silicon carbon precursor material obtained in step S2) to a second reaction vessel, evacuating the second reaction vessel to a pressure of 10 to 100 Kpa, and then passing an atomizing gas through the second reaction vessel to deposit and coat the surface of the silicon carbon precursor material, thereby obtaining a metal-doped silicon carbon composite material, wherein the atomizing gas is obtained by evacuating and heating a cavity containing an outer shell coating solution containing at least a lithium salt, an activator, and an organic solvent, and the flow rate of the atomizing gas is 10 ml / min or more, and the deposition time is 10 minutes or more.

[0013] Preferably, in step S1), the mass ratio of the carbon source to the heteroatom compound is 100:1-5, and / or the mass ratio of the carbon source to the organometallic compound is 100:1-5.

[0014] Preferably, in step S1), the carbon source is one or a mixture of any two or more of phenol resin, furfural resin, urea-formaldehyde resin, bisphenol F epoxy resin, bisphenol A epoxy resin, and bisphenol S epoxy resin; and / or the heteroatom compound is one or a mixture of any two or more of urea, melamine, thiourea, thioacetamide, and phosphoric acid; and / or the organometallic compound is one or a mixture of any two or more of silver trifluoroacetate, silver stearate, silver benzoate, silver diethyldithiocarbamate, silver trifluoromethanesulfonate, 8-hydroxyquinoline copper, copper oleate, basic copper carbonate, and phenylacetyl copper.

[0015] Preferably, in step S2), the volume ratio of chlorosilane to inert gas in the mixed gas is 1 to 5:10, and / or the first reaction tank is evacuated to a pressure of 10 to 100 kPa before the mixed gas is passed into the first reaction tank, and after the mixed gas is passed into the first reaction tank, the degree of vacuum in the first reaction tank is maintained at 100 to 1000 kPa, and / or the flow rate of the mixed gas is set to 10 to 50 ml / min and the introduction time is set to 60 to 300 minutes.

[0016] Preferably, in the outer shell coating solution of step S3), the mass ratio of the lithium salt, activator, and organic solvent is 1-10:0.5-2:100, and / or the lithium salt is one or a mixture of any of lithium borate, lithium tetraborate, lithium pyroborate, lithium metaborate, lithium tetrafluoroborate, and lithium stearate, the activator is one or a mixture of any of CCl3H, CCl2H2, and CClH3, and the organic solvent is one or a mixture of any of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC), and the atomized gas is obtained by evacuating the cavity containing the outer shell coating solution to a pressure of 10-100 Kpa and heating it to a temperature of 200-500°C.

[0017] Preferably, the application of the metal-doped silicon carbon composite material as described above is such that the metal-doped silicon carbon composite material is used as an active material raw material for a battery sheet, preferably an active material raw material for a negative electrode sheet of a lithium ion battery.

[0018] In one aspect of the present application, porous carbon is doped with heteroatoms and metals, using the metallic silver and / or copper to improve the electronic conductivity of the porous carbon material. At the same time, the doping of heteroatoms improves the surface active sites of the porous carbon material, further improving the electronic conductivity of the porous carbon material and the abundance of active sites, effectively improving the silicon storage performance of the porous carbon material and ultimately improving the specific capacity performance of the silicon-carbon composite. In another aspect of the present application, an atomized outer shell coating solution containing a lithium salt and an activator is deposited on a silicon-carbon precursor material to deposit lithium-doped amorphous carbon, preventing the coarsening of silicon crystal grains associated with silicon growth in the core structure. The lithium salt compound is then coated on the surface of the silicon-carbon precursor material. When used as an active material for a battery sheet, the silicon-carbon precursor material can supply lithium ions during the battery charge / discharge process, reducing the battery's irreversible capacity, improving the battery's initial efficiency, and enhancing its rate performance. When used as a negative electrode material for lithium-ion batteries, the material exhibits excellent power performance and initial efficiency, and the manufacturing method provided herein is simple and efficient, economical, practical, and easy to industrialize on a large scale. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is an SEM image of a metal-doped silicon carbon composite material prepared in Example 1 of the present invention. [Figure 2] FIG. 1 is a block diagram of the steps for fabricating a metal-doped silicon carbon composite material according to a specific embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] This embodiment provides a metal-doped silicon carbon composite material having a core-shell structure composed of a core and an outer shell, wherein the core comprises metal- and / or heteroatom-doped porous carbon and nanosilicon, and the outer shell comprises lithium-doped amorphous carbon, and the weight ratio of the outer shell to the core-shell structure is 10 wt % or less. Preferably, in this embodiment, the weight ratio of the outer shell to the core-shell structure is 1-5 wt %.

[0021] In order to improve the electronic conductivity properties of the porous carbon, preferably, in this embodiment, the metal in the core is silver and / or copper, and the heteroatom is one or more of nitrogen, sulfur, and phosphorus, and preferably, in this embodiment, the mass ratio of the metal, porous carbon, and nanosilicon in the core is in the range of 1-5:40-60:40-60, and / or the mass ratio of the heteroatom, porous carbon, and nanosilicon is in the range of 1-5:40-60:40-60.

[0022] Preferably, this embodiment further proposes a method for preparing the metal-doped silicon carbon composite material as described above, which, with reference to FIG. 2, comprises at least the following operation steps: Step S1) is a step of uniformly mixing a carbon source, a heteroatom compound, and / or an organometallic compound, followed by carbonization at a temperature of 500 to 800°C for at least 1 hour to obtain a doped porous carbon. Preferably, in this step S1), the mass ratio of the carbon source, the heteroatom compound, and the organometallic compound is 100:1 to 5:1 to 5. Preferably, in this step S1), the carbon source is a phenolic resin, a furfural resin, a urea-formaldehyde resin, a bisphenol F-type epoxy resin, a bisphenol A-type epoxy resin, a bisphenol B-type epoxy resin, a bisphenol C-type epoxy resin, a bisphenol D-type epoxy resin, a bisphenol E-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol E-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol B-type epoxy resin, a bisphenol C-type epoxy resin, a bisphenol E-type epoxy resin, a bisphenol F-type epoxy resin, a bisphenol B ... Step S1) in which the heteroatom compound is one or a mixture of any of S-type epoxy resins, and / or the heteroatom compound is one or a mixture of any of urea, melamine, thiourea, thioacetamide, and phosphoric acid, and / or the organometallic compound is one or a mixture of any of silver trifluoroacetate, silver stearate, silver benzoate, silver diethyldithiocarbamate, silver trifluoromethanesulfonate, 8-hydroxyquinoline copper, copper oleate, basic copper carbonate, and phenylacetyl copper; Step S2) of transferring the doped porous carbon obtained in step S1) to a first reaction vessel, passing a mixed gas of chlorosilane and an inert gas through the first reaction vessel at a temperature of 300 to 500°C for at least 1 hour to obtain a silicon carbon precursor material, wherein in step S2), the volume ratio of chlorosilane to the inert gas in the mixed gas is preferably 1 to 5:10, and / or the first reaction vessel is evacuated to a pressure of 10 to 100 kPa before passing the mixed gas through the first reaction vessel, and after passing the mixed gas through the first reaction vessel, the degree of vacuum in the first reaction vessel is maintained at 100 to 1000 kPa, and / or the flow rate of the mixed gas is set to 10 to 50 ml / min and the introduction time is set to 60 to 300 minutes; Step S3) is a step of transferring the silicon carbon precursor material obtained in step S2) to a second reaction vessel, evacuating the second reaction vessel to 10 to 100 Kpa, and then passing an atomizing gas through the second reaction vessel to deposit and coat the atomizing gas on the surface of the silicon carbon precursor material, thereby obtaining a metal-doped silicon carbon composite material, wherein the atomizing gas is obtained by evacuating and heating a cavity containing an outer shell coating solution containing at least a lithium salt, an activator, and an organic solvent, the atomizing gas is introduced at a flow rate of 10 ml / min or more, more preferably 10 to 100 ml / min, the deposition time is 10 minutes or more, more preferably 10 to 60 minutes, and preferably the mass ratio of the lithium salt, the activator, and the organic solvent in the outer shell coating solution in step S3) is 1 to 10:0.5 to 2:100, and / or the lithium salt is lithium borate. the activator is one or a mixture of any of CCl3H, CCl2H2, and CClH3, which contributes to the deposition effect of the lithium salt compound on the surface of the silicon carbon precursor material; the organic solvent is one or a mixture of any of dimethyl carbonate (abbreviated as "DMC"), diethyl carbonate (abbreviated as "DEC"), methyl ethyl carbonate (abbreviated as "EMC"), ethylene carbonate (abbreviated as "EC"), and propylene carbonate (abbreviated as "PC"); and the cavity containing the outer shell coating solution is evacuated to 10 to 100 Kpa and heated to 200 to 500°C to obtain an atomized gas (step S3).

[0023] Preferably, this embodiment proposes the application of the metal-doped silicon carbon composite material as described above, in which the metal-doped silicon carbon composite material is used as an active material raw material for a battery sheet, preferably an active material raw material for a negative electrode sheet of a lithium ion battery.

[0024] In order to help those skilled in the art to better understand the technical solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.

[0025] Based on the above embodiments, the present application further provides the following specific examples.

[0026] Example 1: The following operating steps were employed:

[0027] Step S1): 100 g of phenolic resin, 3 g of urea heteroatom compound, and 3 g of silver trifluoroacetate were mixed uniformly in a ball mill and carbonized at a temperature of 600 °C for 3 hours to obtain doped porous carbon.

[0028] Step S2): The doped porous carbon obtained in step S1) above was transferred to a first reaction vessel, which was then evacuated to 50 kPa. A chlorosilane-argon mixed gas (chlorosilane to argon volume ratio of 3:10) was then passed through the vessel, the degree of vacuum in the cavity of the first reaction vessel was maintained at 500 kPa, the vessel was heated to 400°C, the mixed gas introduction flow rate was set to 30 ml / min, and the introduction time was set to 120 minutes. The doped porous carbon and chlorosilane were reacted in the first reaction vessel to obtain a silicon carbon precursor material.

[0029] Step S3): 5 g of lithium borate and 1 g of CClH were added to 100 g of dimethyl carbonate organic solvent and uniformly dispersed to obtain an outer shell coating solution. The silicon-carbon precursor material obtained in step S2 was then transferred to a second reactor, which was then evacuated to 50 kPa. The outer shell coating solution was then transferred to a gasification chamber, which was then evacuated to 50 kPa and heated to 300°C to generate atomized gas. This atomized gas was then passed through the second reactor at a flow rate of 50 ml / min for a deposition time of 30 minutes, and deposited on the surface of the silicon-carbon precursor material to obtain the metal-doped silicon-carbon composite material of Example 1.

[0030] In this application, the metal-doped silicon carbon composite material prepared in Example 1 was subjected to SEM testing, and the test results are shown in Figure 1. As can be seen from Figure 1, this material exhibits a granular structure, and the particle size distribution of the material is uniform and reasonable. Fine agglomerates are observed on the surface, and the particle diameter is between 3 and 7 μm.

[0031] Example 2: The following operating steps were employed.

[0032] Step S1): 100 g of furfural resin, 1 g of melamine, and 1 g of silver stearate were added to a ball mill and mixed uniformly, and then carbonized at a temperature of 500°C for 6 hours to obtain doped porous carbon.

[0033] Step S2): The doped porous carbon obtained in step S1) above was transferred to a first reaction vessel, which was then evacuated to 10 kPa. A chlorosilane-argon mixed gas (chlorosilane to argon volume ratio of 1:10) was then passed through the reaction vessel, the degree of vacuum in the cavity of the first reaction vessel was maintained at 100 kPa, the reaction vessel was heated to 300°C, the mixed gas introduction flow rate was set to 10 ml / min, and the introduction time was set to 300 minutes. The doped porous carbon and chlorosilane were reacted in the first reaction vessel to obtain a silicon carbon precursor material.

[0034] Step S3): 1 g of lithium pyroborate and 0.5 g of CCl2H2 were added to 100 g of diethyl carbonate organic solvent and uniformly dispersed to obtain an outer shell coating solution. The silicon-carbon precursor material obtained in Step S2 was then transferred to a second reactor, which was then evacuated to 10 kPa. The outer shell coating solution was then transferred to a gasification chamber, which was then evacuated to 10 kPa and heated to 200°C to generate atomized gas. This atomized gas was then passed through the second reactor at a flow rate of 100 ml / min for a deposition time of 10 minutes, and deposited on the surface of the silicon-carbon precursor material to obtain the metal-doped silicon-carbon composite material of Example 2.

[0035] Example 3: The following operating steps were employed.

[0036] Step S1): 100 g of urea-formaldehyde resin, 5 g of phosphoric acid, and 5 g of silver benzoate organometallic compound were mixed in a ball mill and then carbonized at 800°C for 1 hour to obtain doped porous carbon.

[0037] Step S2): The doped porous carbon obtained in step S1) above was transferred to a first reaction vessel, which was then evacuated to 100 kPa. A chlorosilane-argon mixed gas (chlorosilane to argon volume ratio of 5:10) was then passed through the vessel, the degree of vacuum in the cavity of the first reaction vessel was maintained at 1000 kPa, the vessel was heated to 500°C, the mixed gas introduction flow rate was set to 50 ml / min, and the introduction time was set to 60 minutes. The doped porous carbon and chlorosilane were reacted in the first reaction vessel to obtain a silicon carbon precursor material.

[0038] Step S3): 10 g of lithium tetrafluoroborate and 2 g of CClH3 were added to 100 g of methyl ethyl carbonate organic solvent and uniformly dispersed to obtain an outer shell coating solution. The silicon-carbon precursor material obtained in Step S2 was then transferred to a second reactor, which was then evacuated to 100 kPa. The outer shell coating solution was then transferred to a gasification chamber, which was then evacuated to 100 kPa and heated to 500°C to generate atomized gas. This atomized gas was then passed through the second reactor at a flow rate of 100 ml / min for a deposition time of 10 minutes, and deposited on the surface of the silicon-carbon precursor material to obtain the metal-doped silicon-carbon composite material of Example 3.

[0039] Example 4: The other technical solutions of this Example 4 are the same as those of Example 1, except that in this Example 4, the urea heteroatom compound 3g is removed in step S1).

[0040] Example 5: The other technical solutions of this Example 5 are the same as those of Example 1, except that in this Example 5, 3 g of silver trifluoroacetate is removed in step S1).

[0041] Comparative Example 1: The other technical solutions of this Comparative Example 1 are the same as those of Example 1, but the only difference is that in this Comparative Example 1, step S1) is omitted, and the doped porous carbon obtained in step S1) is replaced with porous carbon, and steps S2) and S3) are performed. Here, the porous carbon in this Comparative Example 1 was obtained by carbonizing 100 g of phenolic resin at a temperature of 600°C for 3 hours.

[0042] Comparative Example 2: The other technical solutions of this Comparative Example 2 are the same as those of Example 1, but the only difference is that in this Comparative Example 2, the degree of vacuum in the first reaction tank in step S2) is set to atmospheric pressure, and the degree of vacuum in the second reaction tank in step S3) is set to atmospheric pressure.

[0043] Comparative Example 3: The other technical solutions of Comparative Example 3 are the same as those of Example 1, except that in Comparative Example 3, step S3) is omitted and the silicon-carbon precursor material obtained in step S2) is used directly as a silicon-carbon composite material.

[0044] Comparative Example 4: The other technical solutions of this Comparative Example 4 are the same as those of Example 1, but the only difference is that in this Comparative Example 4, steps S2) and S3) are omitted, and the doped porous carbon obtained in step S1) is used as a composite material as is.

[0045] Comparative Example 5: The other technical solutions of this Comparative Example 5 are the same as those of Example 1, but the only difference is that in this Comparative Example 5, step S2) is omitted, and the doped porous carbon obtained in step S1) is used to replace the silicon carbon precursor material obtained in step S2), and step S3) is performed.

[0046] In order to compare and verify the effects of the above Examples and Comparative Examples, the composite materials obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were subjected to the following physicochemical tests in the present application.

[0047] (1) The specific surface area and tap density of each composite material were tested in accordance with the Chinese national standard GB / T 38823-2020 "Silicon Carbon," and the electrical conductivity of each composite material was tested using a four-probe tester. The pore size, pore volume, and powder electrical conductivity parameters of the doped porous carbons of Examples 1 to 5, Comparative Examples 2 to 5, and the porous carbon of Comparative Example 1 were also tested. The test results are shown in Table 1 below.

[0048] (2) Button battery testing: The composite materials corresponding to Examples 1 to 5 and Comparative Examples 1 to 5 were used as negative electrode materials for lithium ion batteries, and button batteries were fabricated according to the following method.

[0049] A binder, conductive agent, and solvent were added to each of the corresponding composite materials, and the mixture was stirred to form a paste. This was then applied to copper foil, dried, and rolled to obtain a negative electrode sheet. The binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP. The proportions of the composite material, SP, LA132, and NMP used were 95g:1g:4g:220mL. The electrolyte was a solution containing LiPF6 as an electrolyte, with a concentration of 1mol / L. Here, the solvent was a mixture of EC and DEC in a volume ratio of 1:1. A metallic lithium sheet was used as the counter electrode, and a polypropylene (PP) membrane was used as the separator.

[0050] Each button battery was assembled in an argon-filled glove box and then tested for electrochemical performance. Specifically, the electrochemical performance was tested using a Wuhan Land CT2001A battery tester with a charge / discharge voltage range of 0.005V to 2.0V and a charge / discharge rate of 0.1C. The test results are shown in Table 1 below.

[0051] The negative electrode sheet of the above button battery was also fully charged and expanded. The specific test process was as follows: After rolling, the thickness D1 of the negative electrode sheet of the button battery was measured, and then the button battery was fully charged to 100% SOC to measure the fully charged thickness D2 of the negative electrode sheet. The expansion rate (expansion rate = (D2 - D1) / D1 * 100%) was calculated, and the test results are shown in Table 1 below. TIFF2026502710000002.tif120170

[0052] As can be seen from the data in Table 1 above, the specific capacity and initial efficiency of the silicon carbon composites prepared in Examples 1 to 5 of the present application are significantly better than those of Comparative Examples 1 to 5. The possible reason for this is that the silicon carbon composites provided in the examples of the present application use doped porous carbon in the core, which significantly improves the electronic conductivity of the material and at the same time significantly reduces the impedance and the expansion of the material during the restricted charge and discharge process; and the lithium salt coated on the outer layer can simultaneously reduce the irreversible capacity and further improve the initial efficiency of the battery using it.

[0053] (3) Soft pouch performance test: The composite materials corresponding to Examples 1 to 5 and Comparative Examples 1 to 5 were doped with 90% artificial graphite to form negative electrode materials (i.e., negative electrode sheets), and positive electrode ternary materials (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), electrolyte, and separator to form a 5 Ah soft pouch battery. The separator was Celgard 2400, and the electrolyte was a LiPF6 solution (the solvent was a 1:1 volumetric mixture of EC and DEC, with a LiPF6 concentration of 1.3 mol / L).

[0054] The following performance tests were carried out on each soft pouch-type battery.

[0055] a. Liquid absorption test: Using a 1 mL burette, V mL of electrolyte was drawn up and one drop was placed on the surface of each negative electrode sheet. The time until the electrolyte was completely absorbed was measured as time t, and the liquid absorption rate S of the negative electrode sheet was calculated as V / t. The test results are shown in Table 2 below.

[0056] b. Liquid retention rate test: The theoretical liquid absorption amount m1 of the corresponding negative electrode sheet is calculated from the parameters of each negative electrode sheet, the weight of the negative electrode sheet is measured as m2, and the negative electrode sheet is then immersed in the electrolyte for 24 hours, the weight of the negative electrode sheet is measured as m3, and the liquid absorption amount m3-m2 of the negative electrode sheet is calculated; and The calculation was carried out according to the formula: Liquid retention rate = (m3-m2)*100% / m1, and the test results are shown in Table 2 below. TIFF2026502710000003.tif60170

[0057] As can be seen from Table 2, the silicon carbon composite materials provided in Examples 1 to 5 have higher liquid absorption and retention capabilities than Comparative Examples 1 to 5. A possible reason for this is that the specific surface area of ​​the silicon carbon composite materials provided in the examples of the present application is large, which can directly improve the liquid absorption and retention capabilities of the silicon carbon composite materials. In addition, the liquid absorption and retention capabilities of Examples 1 to 3 are significantly stronger than those of Examples 4 and 5, which indicates that the simultaneous doping effect of porous carbon with metal and heteroatom is significantly better.

[0058] c. Rate and cycle performance test: A cycle performance test and a rate test were conducted on each soft pouch battery prepared. The test conditions for the cycle performance test were a charge / discharge voltage range of 2.5 to 4.2 V, a temperature of 25±3.0°C, a charge / discharge rate of 0.5 C / 1.0 C, and 500 cycles. The constant current ratio of each soft pouch battery was measured under 2 C rate test conditions, and the measurement results are shown in Table 3 below. TIFF2026502710000004.tif65170

[0059] As can be seen from Table 3, the rate and cycle performance of the soft pouch lithium-ion batteries fabricated using the silicon carbon composites of Examples 1 to 5 are significantly superior to those of Comparative Examples 1 to 4. (The rate and cycle performance of the soft pouch battery of Comparative Example 5 was not tested because the initial discharge specific capacity was too low.) A possible reason for this is that the surface of the silicon carbon composite provided in the examples of this application is coated with a lithium salt, which directly improves the lithium ion insertion and extraction rate of the battery and enhances the constant current rate performance of the battery. In addition, the doped porous carbon used in the core has excellent electronic conductivity, which further improves the constant current rate performance of the battery. Furthermore, the cycle performance of Examples 1 to 3 is significantly superior to that of Examples 4 and 5, indicating that the co-doping effect of porous carbon with metal and heteroatoms is significantly better.

[0060] The present invention is not limited to the details of the illustrative embodiments set forth above, and it will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. Accordingly, the embodiments are to be considered in all respects as illustrative and not limiting, and the scope of the present invention is limited not by the above description but by the appended claims, and all modifications that come within the meaning and range of equivalent elements of the claims are intended to be embraced by the present invention. Any reference numerals appearing in the claims should not be construed as limiting the scope of those claims.

[0061] Furthermore, it should be understood that although the present specification is described according to embodiments, each embodiment does not include only one separate technical solution, and such description manner in the present specification is merely for the purpose of clarifying the explanation, and those skilled in the art should take the present specification as a whole, and the technical solutions in each example can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A metal-doped silicon carbon composite material having a core-shell structure composed of a core and an outer shell, wherein the core comprises metal- and / or heteroatom-doped porous carbon and nanosilicon, and the outer shell comprises lithium-doped amorphous carbon, and the weight ratio of the outer shell to the core-shell structure is 10 wt % or less.

2. 2. The metal-doped silicon carbon composite material according to claim 1, wherein the outer shell occupies 1 to 5 wt % of the core-shell structure.

3. 2. The metal-doped silicon carbon composite material of claim 1, wherein the metal in the core is silver and / or copper, and the heteroatom is one or more of nitrogen, sulfur, and phosphorus.

4. 2. The metal-doped silicon carbon composite material of claim 1, wherein in the core, the mass ratio of the metal, porous carbon, and nanosilicon is in the range of 1-5:40-60:40-60, and / or the mass ratio of the heteroatom, porous carbon, and nanosilicon is in the range of 1-5:40-60:40-60.

5. At least the following operational steps: Step S1) uniformly mixing a carbon source, a heteroatom compound, and / or an organometallic compound, and then carbonizing the mixture at a temperature of 500 to 800°C for at least 1 hour to obtain a doped porous carbon; Step S2) of transferring the doped porous carbon obtained in step S1) to a first reaction vessel, passing a mixed gas of chlorosilane and an inert gas through the first reaction vessel, and passing the mixed gas through the first reaction vessel at a temperature of 300 to 500°C for at least 1 hour to obtain a silicon carbon precursor material; 5. The method for producing a metal-doped silicon carbon composite material according to claim 1, further comprising: step S3), in which the silicon carbon precursor material obtained in step S2) is transferred to a second reaction vessel, the second reaction vessel is evacuated to a pressure of 10 to 100 KPa, and an atomizing gas is passed through the second reaction vessel to deposit and coat the surface of the silicon carbon precursor material, thereby obtaining a metal-doped silicon carbon composite material; the atomizing gas is obtained by evacuating and heating a cavity containing an outer shell coating solution containing at least a lithium salt, an activator, and an organic solvent, the atomizing gas is introduced at a flow rate of 10 mL / min or more, and the deposition time is 10 minutes or more.

6. 6. The method for producing a metal-doped silicon carbon composite material according to claim 5, wherein in step S1), the mass ratio of the carbon source to the heteroatom compound is 100:1-5, and / or the mass ratio of the carbon source to the organometallic compound is 100:1-5.

7. 6. The method for producing a metal-doped silicon carbon composite material according to claim 5, wherein in step S1), the carbon source is one or a mixture of any two or more of a phenol resin, a furfural resin, a urea-formaldehyde resin, a bisphenol F type epoxy resin, a bisphenol A type epoxy resin, and a bisphenol S type epoxy resin; and / or the heteroatom compound is one or a mixture of any two or more of a urea, a melamine, a thiourea, a thioacetamide, and a phosphoric acid; and / or the organometallic compound is one or a mixture of any two or more of a silver trifluoroacetate, a silver stearate, a silver benzoate, a silver diethyldithiocarbamate, a silver trifluoromethanesulfonate, 8-hydroxyquinoline copper, a copper oleate, a basic copper carbonate, and a phenylacetyl copper.

8. 6. The method for producing a metal-doped silicon carbon composite material according to claim 5, wherein in step S2), a volume ratio of chlorosilane to inert gas in the mixed gas is 1 to 5:10; and / or before passing the mixed gas into the first reaction tank, the first reaction tank is evacuated to a pressure of 10 to 100 kPa, and after passing the mixed gas into the first reaction tank, the degree of vacuum in the first reaction tank is maintained at 100 to 1000 kPa; and / or the mixed gas is introduced at a flow rate of 10 to 50 ml / min for an introduction time of 60 to 300 minutes.

9. In step S3), the mass ratio of the lithium salt, the activator, and the organic solvent is 1-10:0.5-2:100, and / or the lithium salt is one or a mixture of any of lithium borate, lithium tetraborate, lithium pyroborate, lithium metaborate, lithium tetrafluoroborate, and lithium stearate, and the activator is CCl ３ H, CCl ２ H ２ , CClH ３ 6. The method for producing a metal-doped silicon carbon composite material according to claim 5, wherein the organic solvent is one or a mixture of any of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC), and the atomized gas is obtained by evacuating a cavity containing the outer shell coating solution to a pressure of 10 to 100 Kpa and heating the cavity to a temperature of 200 to 500°C.

10. 5. The application of the metal-doped silicon carbon composite material according to any one of claims 1 to 4, characterized in that the metal-doped silicon carbon composite material is used as an active material raw material for a battery sheet, preferably an active material raw material for a negative electrode sheet of a lithium-ion battery.

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