Silicon-carbon negative electrode sheet with interface buffer layer and preparation method and application thereof

Abstract

The embodiment of the present application relates to a kind of silicon-carbon negative pole piece with interface buffer layer and its preparation method and application, wherein, preparation method includes: preparation non-through microporous copper foil, the pore size of non-through microporous is 10 μm-20 μm;Non-through microporous copper foil is immersed in soluble carbon precursor solution under vacuum condition, carbonization treatment is carried out after drying, and non-through microporous copper foil with carbon layer is obtained;Non-through microporous copper foil with carbon layer is placed in deposition furnace, deposition furnace is heated under protective atmosphere, then silicon source gas is introduced into deposition furnace to carry out silicon deposition, and silicon-carbon negative pole piece with interface buffer layer is obtained.The preparation method provided in the embodiment of the present application not only solves the volume expansion problem of silicon, improves the cycle stability of battery, but also solves the problem of conductivity, improves the rate performance of battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials, and in particular to a silicon-carbon negative electrode sheet with an interface buffer layer, its preparation method, and its application. Background Technology

[0002] Silicon, with its ultra-high theoretical specific capacity (approximately 4200 mAh / g), is considered one of the most promising candidates to replace traditional graphite anodes and improve the energy density of lithium-ion batteries. However, silicon undergoes a massive volume expansion (over 300%) during lithium insertion / extraction, which leads to the pulverization of active material particles, their detachment from the current collector, and repeated rupture and regeneration of the solid electrolyte interphase (SEI), ultimately resulting in rapid capacity decay and poor cycle life.

[0003] To address these issues, existing technologies typically employ methods such as nano-sizing of silicon materials, compositing them with carbon materials, or using special binders and electrolyte additives. While these methods alleviate the volume expansion problem to some extent, the interfacial failure issue between silicon and the current collector copper foil remains unresolved. Traditional coating methods apply silicon-carbon composite materials to the copper foil surface. During charge and discharge, the volume change of silicon causes significant stress between the active layer and the copper foil, leading to interfacial delamination, increased contact resistance, and conductive network failure, thus severely impacting the battery's cycle stability and rate performance.

[0004] Therefore, how to effectively anchor silicon materials, buffer their volume effect, and maintain the integrity of the electrode structure and excellent electronic conduction is a key challenge that current silicon anode technology urgently needs to overcome. Summary of the Invention

[0005] The purpose of this invention is to address the deficiencies of existing technologies by providing a silicon-carbon anode sheet with an interface buffer layer, its preparation method, and its application.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a silicon-carbon negative electrode sheet with an interface buffer layer, the method comprising: Prepare non-penetrating microporous copper foil, wherein the pore size of the non-penetrating micropore is 10μm-20μm; Under vacuum conditions, non-penetrating microporous copper foil is immersed in a soluble carbon precursor solution, dried, and then carbonized to obtain non-penetrating microporous copper foil with a carbon layer. The non-penetrating microporous copper foil with a carbon layer is placed in a deposition furnace. Under a protective atmosphere, the deposition furnace is heated, and then silicon source gas is introduced into the deposition furnace to perform silicon deposition, thereby obtaining a silicon-carbon anode sheet with an interface buffer layer.

[0007] Preferably, the thickness of the non-penetrating microporous copper foil is 10μm-50μm.

[0008] Preferably, the preparation of the non-penetrating microporous copper foil specifically involves: Laser and electrochemical etching are used to drill holes in copper foil.

[0009] Preferably, the soluble carbon precursor solution includes one or more combinations of polymers, resins, and bituminous materials; The polymers include one or more of glucose, sucrose, fructose, cellulose, starch, polyvinyl alcohol, styrene rubber, carboxymethyl cellulose, polystyrene, polyethylene glycol, and polyvinylpyrrolidone. The resins include one or more of phenolic resin, epoxy resin, melamine resin, and furfural resin; The asphalt types include one or more of coal tar pitch, petroleum asphalt, and secondary coal tar pitch.

[0010] Preferably, the solid content of the soluble carbon precursor solution is 1%-60%.

[0011] Preferably, the vacuum level is -0.1MPa to -60MPa; the drying temperature is 100℃-150℃, and the drying time is 10-60 hours.

[0012] Preferably, the carbonization treatment conditions are as follows: the equipment is one of a tube furnace, box furnace, roller kiln, tunnel kiln, or pusher kiln; the temperature is 400℃-1000℃; the heating rate is 1℃ / min-20℃ / min; and the time is 1 hour-60 hours; the thickness of the carbon layer is 10nm-500nm.

[0013] Preferably, the silicon deposition conditions are: temperature 440℃-500℃, time 330min-400min, and the silicon source gas includes one or more of silane, silane, and dichlorosilane; the volume of silicon deposition accounts for 30%-100% of the volume of the non-penetrating microporous copper foil.

[0014] In a second aspect, the present invention provides a silicon-carbon anode sheet with an interface buffer layer, wherein the silicon-carbon anode sheet with an interface buffer layer is prepared by any of the preparation methods described in the first aspect above.

[0015] Thirdly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the silicon-carbon negative electrode sheet with an interface buffer layer as described in the second aspect.

[0016] This invention provides a method for preparing a silicon-carbon negative electrode sheet with an interface buffer layer. The method involves preparing non-penetrating micropores on a copper foil, followed by impregnation and carbonization to deposit a carbon layer within these micropores. The carbon layer ensures preferential silicon deposition within the micropores. Furthermore, its flexibility and toughness act as an effective conductive medium between the silicon and copper foil, and as an interface buffer layer to prevent silicon expansion. During silicon expansion and contraction, it absorbs some stress, preventing stress from being directly transferred to the copper foil and causing delamination between the silicon and copper foil. This ensures point contact at the silicon / copper interface, improving the overall conductivity of the electrode sheet. The spatial confinement of the non-penetrating micropores also restricts the direction of silicon volume expansion, effectively mitigating the risk of active material pulverization and detachment from the current collector caused by repeated silicon expansion and contraction. Additionally, the copper foil forms a tight contact with the silicon through the carbon layer, constructing a highly efficient three-dimensional conductive network, significantly reducing interface contact resistance, and thus greatly improving the rate performance of the battery. In summary, this preparation method not only solves the problem of silicon volume expansion and improves the cycle stability of the battery, but also solves the conductivity problem and improves the rate performance of the battery. Attached Figure Description

[0017] Figure 1 A flowchart illustrating a method for preparing a silicon-carbon negative electrode sheet with an interface buffer layer, provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a silicon-carbon negative electrode sheet with an interface buffer layer provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] This invention provides a method for preparing a silicon-carbon negative electrode sheet with an interface buffer layer, the process of which is as follows: Figure 1 As shown, it includes the following steps: Step 110: Prepare a non-penetrating microporous copper foil with a pore size of 10μm-20μm; Specifically, the thickness of the non-penetrating microporous copper foil is 10μm-50μm. To obtain non-penetrating microporous copper foil with uniform pore size, perforations can be made in the copper foil using methods such as laser drilling or electrochemical etching, with electrochemical etching being the preferred method. The pore size of the non-penetrating micropores is preferably 15μm. Pore size refers to the diameter or characteristic size of the micropore and is an important parameter describing its pore structure. Pore size is measured using the gas adsorption method with an ASAP2460 fully automated specific surface area and porosity analyzer.

[0021] Step 120: Under vacuum conditions, the non-penetrating microporous copper foil is immersed in a soluble carbon precursor solution, dried, and then carbonized to obtain a non-penetrating microporous copper foil with a carbon layer. Specifically, the vacuum level can range from -0.1 MPa to -60 MPa. The soluble carbon precursor solution can include one or more of the following: polymers, resins, and bitumen. Polymers can include one or more of glucose, sucrose, fructose, cellulose, starch, polyvinyl alcohol, styrene rubber, carboxymethyl cellulose, polystyrene, polyethylene glycol, and polyvinylpyrrolidone. Resins can include one or more of phenolic resins, epoxy resins, melamine resins, and furfural resins. Bitumen can include one or more of coal tar pitch, petroleum tar pitch, and secondary coal tar pitch.

[0022] The solid content of the soluble carbon precursor solution is 1%-60%.

[0023] The soaking time is 10-20 hours. The drying temperature is 100℃-150℃, and the time is 10-60 hours.

[0024] It should be noted that during the drying process, the soluble carbon precursor solution may separate from the copper foil due to the difference in interfacial tension under the influence of temperature. Therefore, the dried soluble carbon precursor outside the non-penetrating micropores can be removed by physical means, such as repeated scraping, ensuring that the soluble carbon precursor is only retained in the non-penetrating micropores, providing anchoring points for subsequent silicon deposition.

[0025] Specific conditions for carbonization treatment: The equipment is one of the following: tube furnace, box furnace, roller kiln, tunnel kiln, or pusher kiln; the inert atmosphere is one or more of hydrogen, nitrogen, and argon; the temperature is 400℃-1000℃; the heating rate is 1℃ / min-20℃ / min; and the time is 1 hour-60 hours. The thickness of the carbon layer is 10nm-500nm.

[0026] Step 130: Place the non-penetrating microporous copper foil with a carbon layer in a deposition furnace. Under a protective atmosphere, heat the deposition furnace and then introduce silicon source gas into the deposition furnace to perform silicon deposition, thereby obtaining a silicon-carbon anode sheet with an interface buffer layer.

[0027] Specifically, the protective atmosphere can be nitrogen and / or argon. The heating process for the deposition furnace is as follows: introduce the protective gas at a flow rate of 10 L / min-60 L / min, heat to 440℃-500℃, and hold at that temperature for 30-40 minutes. The deposition furnace can specifically include a tube furnace, a pusher kiln, or a box furnace.

[0028] The silicon deposition conditions are: temperature 440℃-500℃, time 330min-400min. The silicon source gas can specifically include one or more of silane, silane, and dichlorosilane, and the flow rate of the silicon source gas can be 2L / min-30L / min. The volume percentage of silicon deposition in the non-penetrating microporous copper foil is [30%-100%]. It should be noted that the volume percentage of silicon deposition here refers to the proportion of the volume of silicon in the micropores of the non-penetrating microporous copper foil. For example, 100% means that silicon has occupied the entire space of the micropores. The formula for calculating the volume percentage of silicon deposition is as follows: Hole volume = (M) 原Cu -M 剩余Cu ) / ρ Cu ; M 硅1 =ρsilicon * pore volume; M 硅2 =M 总Cu -M 剩余Cu ; Silicon deposition volume percentage = M 硅2 / M 硅1 ; Among them, M 原Cu M represents the quality of copper foil without non-penetrating micropores. 剩余Cu The mass of the copper foil after perforation is indicated; the perforation volume represents the total volume of micropores in the non-penetrating micro-perforated copper foil; M 硅1 M represents the total mass of silicon that can theoretically be deposited in the micropores of a non-penetrating microporous copper foil; 硅2 Indicates the actual amount of silicon deposited; M 总Cu This indicates the quality of the non-penetrating microporous copper foil after silicon deposition.

[0029] like Figure 2 As shown, orange represents copper foil, black represents C, and yellow represents Si. During this process, silicon readily adsorbs onto the defect sites of carbon atoms in the carbon layer (Si-C or physical adsorption), solving the problem of silicon's difficulty in nucleation and uneven deposition on smooth copper foil. Subsequently, the silicon-hydrogen bonds in the silane dissociate and nucleate, leading to grain growth and realizing the deposition of silicon in non-penetrating micropores.

[0030] This invention provides a method for preparing a silicon-carbon negative electrode sheet with an interface buffer layer. The method involves preparing non-penetrating micropores on a copper foil, followed by impregnation and carbonization to deposit a carbon layer within these micropores. The carbon layer ensures preferential silicon deposition within the micropores. Furthermore, its flexibility and toughness act as an effective conductive medium between the silicon and copper foil, and as an interface buffer layer to prevent silicon expansion. During silicon expansion and contraction, it absorbs some stress, preventing stress from being directly transferred to the copper foil and causing delamination between the silicon and copper foil. This ensures point contact at the silicon / copper interface, improving the overall conductivity of the electrode sheet. The spatial confinement of the non-penetrating micropores also restricts the direction of silicon volume expansion, effectively mitigating the risk of active material pulverization and detachment from the current collector caused by repeated silicon expansion and contraction. Additionally, the copper foil forms a tight contact with the silicon through the carbon layer, constructing a highly efficient three-dimensional conductive network, significantly reducing interface contact resistance, and thus greatly improving the rate performance of the battery. In summary, this preparation method not only solves the problem of silicon volume expansion and improves the cycle stability of the battery, but also solves the conductivity problem and improves the rate performance of the battery.

[0031] The silicon-carbon negative electrode sheet with an interface buffer layer provided by this invention can be applied to lithium-ion batteries.

[0032] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the specific process of preparing a silicon-carbon anode sheet with an interface buffer layer using the method provided in the above embodiments of the present invention, as well as the electrochemical characteristics of the silicon-carbon anode sheet with an interface buffer layer obtained therefrom.

[0033] Example 1 The first step involved preparing a non-penetrating microporous copper foil via electrochemical etching. The thickness of the non-penetrating microporous copper foil was 15 μm, and the pore size of the non-penetrating micropores was 10 μm. The electrochemical etching conditions were as follows: the etching solution consisted of 0.5 mol / L HCl, 0.5 mol / L C2H2O4, 0.1 mol / L NH4Cl, 0.1 mol / L FeCl3, and 0.5 mol / L HgCl2. The etching tank served as the cathode, the copper foil as the anode, a 25V direct current was applied, and the residence time of the copper foil in the etching solution was 20 s.

[0034] The second step involves immersing the non-penetrating microporous copper foil in a 25% solid content polyvinylpyrrolidone aqueous solution for 10 hours under a vacuum of -0.1 MPa. Then, the vacuum oven is heated to 100°C and dried for 12 hours. The polyvinylpyrrolidone drying solution outside the non-penetrating micropores is removed by physical scraping. The non-penetrating microporous copper foil is then transferred to a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The temperature is maintained for 2 hours to obtain a non-penetrating microporous copper foil with a carbon layer, wherein the thickness of the carbon layer is 30 nm.

[0035] The third step involves transferring the non-penetrating microporous copper foil to the substrate of a pusher furnace, introducing nitrogen gas at a flow rate of 10 L / min, heating to 440°C, and holding at that temperature for 30 min. Then, silane is introduced at a flow rate of 6 L / min, and the temperature is maintained for another 400 min, resulting in a silicon-carbon negative electrode sheet with an interface buffer layer. The volume of silicon deposited accounts for 65% of the volume of the non-penetrating microporous copper foil.

[0036] Subsequently, coin-type half-cells were assembled and tested using the prepared silicon-carbon negative electrode sheet with an interface buffer layer, as detailed below: First, the silicon-carbon negative electrode sheet with an interface buffer layer prepared above is cut into shape.

[0037] Then, the CR2032 coin cell was assembled in an argon-filled glove box. The coin cell used lithium metal sheets as the counter and reference electrodes, Celgard 2500 as the separator, and 1 mol / L LiPF6 as the electrolyte. The electrolyte solvent consisted of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio.

[0038] Finally, at room temperature (25℃), constant current charge-discharge tests at different current densities were simultaneously conducted on the LAND test system. The test voltage range was 0.005~2V. First, the voltage was discharged to 0.005V at 0.1C (1C=1000mAh / g), left to stand for 5 minutes, and then charged to 2V at 0.1C. The specific capacity of each discharge and charge was recorded, and the coulombic efficiency of the first cycle and the discharge capacity retention rate at the same rate for 100 cycles were calculated. At the same time, the expansion rate of the electrode after 100 cycles was tested. The test results are shown in Table 1. Specifically, the expansion rate test involves using a micrometer to measure the thickness of the electrode before cycling, taking the median value, and after 100 cycles, using dimethyl carbonate (DMC) to remove the solid electrolyte interphase (SEI) film on the surface. After drying, the same method is used to measure the electrode thickness, taking the median value, and then calculating the expansion rate as the ratio of the difference between the expanded electrode thickness and the original electrode thickness to the original electrode thickness.

[0039] Example 2 The first step involved preparing a non-penetrating microporous copper foil via electrochemical etching. The thickness of the non-penetrating microporous copper foil was 25 μm, and the pore size of the non-penetrating micropores was 15 μm. The electrochemical etching conditions were as follows: the etching solution consisted of 1 mol / L HCl, 1 mol / L C2H2O4, 0.3 mol / L NH4Cl, 0.5 mol / L FeCl3, and 1 mol / L HgCl2. The etching tank served as the cathode, the copper foil as the anode, a 25V direct current was applied, and the residence time of the copper foil in the etching solution was 80 s.

[0040] The second step involves immersing the non-penetrating microporous copper foil in a 15% solid content alcohol-soluble phenolic resin solution (ethanol) for 15 hours under a vacuum of -0.3 MPa. Then, the vacuum oven is heated to 120°C and dried for 24 hours. The alcohol-soluble phenolic resin drying solution outside the non-penetrating micropores is removed by physical scraping. The non-penetrating microporous copper foil is then transferred to a tube furnace and heated to 800°C at a rate of 5°C / min under an argon atmosphere, and held for 3 hours to obtain a non-penetrating microporous copper foil with a carbon layer, the thickness of which is 50 nm.

[0041] The third step involves transferring the non-penetrating microporous copper foil to a substrate in a tube furnace, introducing argon gas at a flow rate of 12 L / min, heating to 480°C, and holding at that temperature for 30 min. Then, silane is introduced at a flow rate of 5 L / min, and the temperature is maintained for another 400 min, resulting in a silicon-carbon anode sheet with an interface buffer layer. The volume of silicon deposited accounts for 55% of the volume of the non-penetrating microporous copper foil.

[0042] The testing process is the same as in Example 1.

[0043] Example 3 The first step is to prepare non-penetrating microporous copper foil by laser drilling. The thickness of the non-penetrating microporous copper foil is 50 μm, the diameter of the non-penetrating micropores is 20 μm, and the laser drilling method uses a CO2 laser drill and a UVDPSS laser drill. The laser beam is focused to a size of 20 μm and the processing time is 10 s.

[0044] The second step involves immersing the non-penetrating microporous copper foil in a 15% tetrahydrofuran dissolved petroleum asphalt organic solution for 20 hours under a vacuum of -0.2 MPa. Then, the vacuum oven is heated to 150°C and dried for 10 hours. The dried tetrahydrofuran dissolved petroleum asphalt organic solution outside the non-penetrating micropores is removed by physical scraping. The non-penetrating microporous copper foil is then transferred to a tube furnace and heated to 900°C at a rate of 20°C / min under a nitrogen atmosphere, and held for 4 hours to obtain a non-penetrating microporous copper foil with a carbon layer, the thickness of which is 100 nm.

[0045] The third step involves transferring the non-penetrating microporous copper foil to a substrate in a box furnace. Nitrogen gas is introduced at a flow rate of 30 L / min, the temperature is raised to 480°C, and held for 40 min. Then, dichlorosilane is introduced at a flow rate of 30 L / min, and the temperature is maintained for another 330 min, resulting in a silicon-carbon negative electrode sheet with an interface buffer layer. The volume of silicon deposited accounts for 98% of the volume of the non-penetrating microporous copper foil.

[0046] The testing process is the same as in Example 1.

[0047] Example 4 The first step involved preparing a non-penetrating microporous copper foil via electrochemical etching. The thickness of the non-penetrating microporous copper foil was 10 μm, and the pore size of the non-penetrating micropores was 20 μm. The electrochemical etching conditions were as follows: the etching solution consisted of 1.5 mol / L HCl, 2 mol / L C₂H₂O₄, 0.5 mol / L NH₄Cl, 1 mol / L FeCl₃, and 1.5 mol / L HgCl₂. The etching tank served as the cathode, the copper foil as the anode, a 25V direct current was applied, and the residence time of the copper foil in the etching solution was 120 s.

[0048] The second step involves immersing the non-penetrating microporous copper foil in a 60% glucose solution under a vacuum of -60 MPa for 18 hours. The equipment is then heated to 100°C and dried for 60 hours. The glucose solution outside the non-penetrating micropores is removed by physical scraping. The non-penetrating microporous copper foil is then transferred to a tube furnace and heated to 400°C at a rate of 1°C / min under a hydrogen atmosphere. This temperature is maintained for 60 hours to obtain a non-penetrating microporous copper foil with a carbon layer, the thickness of which is 35 nm.

[0049] The third step involves transferring the non-penetrating microporous copper foil to the substrate of a pusher furnace, introducing nitrogen gas at a flow rate of 60 L / min, heating to 440°C, and holding at that temperature for 30 min. Then, silane is introduced at a flow rate of 7 L / min, and the temperature is maintained for another 400 min, resulting in a silicon-carbon negative electrode sheet with an interface buffer layer. The volume of silicon deposited is 70% of the volume of the non-penetrating microporous copper foil.

[0050] The testing process is the same as in Example 1.

[0051] Example 5 The first step is to prepare non-penetrating microporous copper foil by laser drilling. The thickness of the non-penetrating microporous copper foil is 35μm, the diameter of the non-penetrating micropores is 12μm, and the laser drilling method uses a CO2 laser drill and a UVDPSS laser drill. The laser beam focusing size is 15μm, and the processing time is 7s.

[0052] The second step involves immersing the non-penetrating microporous copper foil in a 1% tetrahydrofuran-dissolved secondary coal tar pitch organic solution for 20 hours under a vacuum of -20 MPa. Then, the vacuum oven is heated to 150°C and dried for 30 hours. The tetrahydrofuran-dissolved secondary coal tar pitch organic solution is removed from the non-penetrating micropores by physical scraping. The non-penetrating microporous copper foil is then transferred to a tube furnace and heated to 1000°C at a rate of 10°C / min under a nitrogen atmosphere, and held for 4 hours to obtain a non-penetrating microporous copper foil with a carbon layer, the thickness of which is 20 nm.

[0053] The third step involves transferring the non-penetrating microporous copper foil to a substrate in a box furnace. Nitrogen gas is introduced at a flow rate of 12 L / min, the temperature is raised to 480°C, and held for 30 min. Then, silane is introduced at a flow rate of 2 L / min, and the temperature is maintained for another 380 min, resulting in a silicon-carbon anode sheet with an interface buffer layer. The volume of silicon deposited is 55% of the volume of the non-penetrating microporous copper foil.

[0054] The testing process is the same as in Example 1.

[0055] Comparative Example 1 This comparative example involves preparing silicon-carbon anode sheets on conventional copper foil (without non-penetrating micropores).

[0056] The first step involves immersing conventional copper foil in a 25% solid content polyvinylpyrrolidone aqueous solution for 10 hours under a vacuum of -0.1 MPa. Then, the vacuum oven is heated to 100°C and dried for 12 hours. The polyvinylpyrrolidone drying solution outside the non-penetrating micropores is removed by physical scraping. The non-penetrating micropore copper foil is then transferred to a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The temperature is then maintained for 2 hours to obtain a non-penetrating micropore copper foil with a carbon layer, wherein the thickness of the carbon layer is 30 nm.

[0057] The second step involves transferring the non-penetrating microporous copper foil to the substrate of a pusher kiln, introducing nitrogen gas at a flow rate of 10 L / min, heating to 440°C, holding at that temperature for 30 min, then introducing silane at a flow rate of 6 L / min, and continuing to hold at that temperature for 400 min to obtain a silicon-carbon negative electrode sheet.

[0058] The testing process is the same as in Example 1.

[0059] Comparative Example 2 This comparative example did not undergo carbonization treatment; silicon deposition was performed directly on non-penetrating microporous copper foil.

[0060] The first step involved preparing a non-penetrating microporous copper foil via electrochemical etching. The thickness of the non-penetrating microporous copper foil was 25 μm, and the pore size of the non-penetrating micropores was 15 μm. The electrochemical etching conditions were as follows: the etching solution consisted of 1 mol / L HCl, 1 mol / L C2H2O4, 0.3 mol / L NH4Cl, 0.5 mol / L FeCl3, and 1 mol / L HgCl2. The etching tank served as the cathode, the copper foil as the anode, a 25V direct current was applied, and the residence time of the copper foil in the etching solution was 80 s.

[0061] The second step involves directly transferring the non-penetrating microporous copper foil to a substrate in a tube furnace. Argon gas is introduced at a flow rate of 12 L / min, the temperature is raised to 480°C, and held for 30 min. Then, silane is introduced at a flow rate of 5 L / min, and the temperature is maintained for another 400 min to obtain the negative electrode. The volume of silicon deposited is 50% of the volume of the non-penetrating microporous copper foil.

[0062] The testing process is the same as in Example 1.

[0063] Comparative Example 3 This comparative example did not use physical scraping to remove the carbon layer outside the non-penetrating micropores.

[0064] The first step is to prepare non-penetrating microporous copper foil by laser drilling. The thickness of the non-penetrating microporous copper foil is 50 μm, the diameter of the non-penetrating micropores is 20 μm, and the laser drilling method uses a CO2 laser drill and a UVDPSS laser drill. The laser beam is focused to a size of 20 μm and the processing time is 10 s.

[0065] The second step involves immersing the non-penetrating microporous copper foil in a 15% tetrahydrofuran dissolved petroleum asphalt organic solution for 20 hours under a vacuum of -0.2 MPa. Then, the vacuum oven is heated to 150°C and dried for 10 hours. The non-penetrating microporous copper foil is then directly transferred to a tube furnace and heated to 900°C at a rate of 20°C / min under a nitrogen atmosphere. The temperature is then maintained for 4 hours to obtain a non-penetrating microporous copper foil with a carbon layer, wherein the thickness of the carbon layer is 100 nm.

[0066] The third step involves transferring the non-penetrating microporous copper foil to a substrate in a box furnace. Nitrogen gas is introduced at a flow rate of 30 L / min, the temperature is raised to 480°C, and held for 40 min. Then, dichlorosilane is introduced at a flow rate of 30 L / min, and the temperature is maintained for another 330 min, resulting in a silicon-carbon anode sheet with an interface buffer layer. The volume of silicon deposited is 98% of the volume of the non-penetrating microporous copper foil.

[0067] The testing process is the same as in Example 1.

[0068] Comparative Example 4 This comparative example involves silicon deposition directly on conventional copper foil.

[0069] Conventional copper foil was placed in the substrate of a box furnace, and argon gas was introduced at a flow rate of 12 L / min. The temperature was raised to 480°C and held for 30 min. Then, silane was introduced at a flow rate of 5 L / min and the temperature was held for another 400 min to obtain a negative electrode with an interface buffer layer.

[0070] Table 1 summarizes the test results of Examples 1-5 and Comparative Examples 1-4 of the present invention.

[0071] Table 1 As shown in Table 1, after 100 cycles, the discharge capacity retention rate of the button half-cells of Examples 1-5 of the present invention is much higher than that of Comparative Examples 1-4. Furthermore, the higher the discharge capacity retention rate, the lower the expansion rate of the electrode. This indicates that the proportion of silicon detachment from copper foil in the silicon-carbon negative electrode with interface buffer layer in the embodiments of the present invention is very small. The dual effect of micropores and carbon layer provides favorable conditions for silicon volume change. This preparation method not only solves the problem of silicon volume expansion and improves the cycle stability of the battery, but also solves the conductivity problem and improves the rate performance of the battery.

[0072] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-carbon negative electrode sheet with an interface buffer layer, characterized in that, The preparation method includes: Prepare non-penetrating microporous copper foil, wherein the pore size of the non-penetrating micropore is 10μm-20μm; Under vacuum conditions, non-penetrating microporous copper foil is immersed in a soluble carbon precursor solution, dried, and then carbonized to obtain non-penetrating microporous copper foil with a carbon layer. The non-penetrating microporous copper foil with a carbon layer is placed in a deposition furnace. Under a protective atmosphere, the deposition furnace is heated, and then silicon source gas is introduced into the deposition furnace to perform silicon deposition, thereby obtaining a silicon-carbon anode sheet with an interface buffer layer.

2. The preparation method according to claim 1, characterized in that, The thickness of the non-penetrating microporous copper foil is 10μm-50μm.

3. The preparation method according to claim 1, characterized in that, The specific steps for preparing the non-penetrating microporous copper foil are as follows: Laser and electrochemical etching are used to drill holes in copper foil.

4. The preparation method according to claim 1, characterized in that, Soluble carbon precursor solutions include one or more of the following: polymers, resins, and bituminous materials. The polymers include one or more of glucose, sucrose, fructose, cellulose, starch, polyvinyl alcohol, styrene rubber, carboxymethyl cellulose, polystyrene, polyethylene glycol, and polyvinylpyrrolidone. The resins include one or more of phenolic resin, epoxy resin, melamine resin, and furfural resin; The asphalt types include one or more of coal tar pitch, petroleum asphalt, and secondary coal tar pitch.

5. The preparation method according to claim 1, characterized in that, The solid content of the soluble carbon precursor solution is 1%-60%.

6. The preparation method according to claim 1, characterized in that, The vacuum level is -0.1MPa to -60MPa; the drying temperature is 100℃-150℃, and the drying time is 10-60 hours.

7. The preparation method according to claim 1, characterized in that, The carbonization treatment conditions are as follows: the equipment is one of the following: tube furnace, box furnace, roller kiln, tunnel kiln, and pusher kiln; the temperature is 400℃-1000℃; the heating rate is 1℃ / min-20℃ / min; and the time is 1 hour-60 hours. The thickness of the carbon layer is 10nm-500nm.

8. The preparation method according to claim 1, characterized in that, The silicon deposition conditions are: temperature 440℃-500℃, time 330min-400min, and the silicon source gas includes one or more of silane, silane, and dichlorosilane; the volume of silicon deposition accounts for 30%-100% of the volume of the non-penetrating microporous copper foil.

9. A silicon-carbon negative electrode sheet with an interface buffer layer, characterized in that, The silicon-carbon negative electrode sheet with an interface buffer layer is prepared by any one of the preparation methods described in claims 1-8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the silicon-carbon negative electrode sheet with an interface buffer layer as described in claim 9.

Images