High-performance silicon-based composite negative electrode sheet and preparation method and application thereof

Abstract

The present application belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a high-performance silicon-based composite negative electrode sheet and a preparation method and application thereof. The present application provides a preparation method of a high-performance silicon-based composite negative electrode sheet, which is simple to operate, has a remarkable effect, and is easy to scale up, and has high commercial value and the advantages of being easy to scale up. The present application can improve the performance of a negative electrode sheet containing a silicon-based active material in a lithium ion secondary battery by adding defective carbon nanotubes, use the strong local stress generated by the silicon-based active material in the charging expansion stage to cause high strain on the defective carbon nanotubes, enhance the chemical activity of atoms at the defect sites, thereby generating a "stress-chemical interface coupling reaction" between the silicon-based clusters and lithium atoms, in-situ anchoring the silicon-based clusters, avoiding the loss of electrical contact, and at the same time, the silicon-based clusters can also separate the defective carbon nanotube bundles, enhancing the transmission rate of lithium ions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a silicon-based negative electrode material, a preparation method thereof, and a lithium ion battery or lithium ion secondary battery comprising the same, and specifically relates to a high-performance silicon-based composite negative electrode sheet and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion secondary batteries have been widely used in various electronic products, electric vehicles, and large-scale energy storage devices due to their high energy density and good cycle performance. With the development of the market, higher requirements are placed on their performance, and the rapid iteration of lithium ion secondary batteries has made certain progress in terms of energy density and cycle life. In particular, with the introduction of silicon-based negative electrode materials, the capacity of lithium ion secondary battery negative electrodes has made great progress, which is due to the high theoretical capacity of silicon-based negative electrode materials. Among them, elemental silicon shows a theoretical capacity of about 4200 mAh / g, and sub-silicon SiO x has a theoretical capacity of about 2400 mAh / g.

[0003] Silicon-based negative electrode materials are the preferred choice for improving the performance of lithium ion secondary batteries, but their large-scale application has been severely restricted by problems such as high volume expansion rate. This can cause the electrode to crack and even powder off, and the fresh silicon surface generated by fragmentation will consume the electrolyte and form a new SEI film. With the cycle, the silicon-based negative electrode will continuously undergo powdering and SEI formation processes, consuming electrolyte and causing irreversible capacity and rapid decay of electrode capacity.

[0004] During the lithiumization cycle, the continuous expansion and cracking process can cause some silicon-based particles to lose electrical contact, exhibit electrochemical inertness, and some silicon-based particles become "dead silicon". Some of the lithium ions embedded therein are also deactivated and cannot be removed, resulting in irreversible capacity and seriously affecting the cycle life of the silicon-based negative electrode.

[0005] Currently, silicon-based materials can only be added to graphite negative electrodes in a low content to form a composite material for use. Conventional silicon-based negative electrode structure design methods include core-shell, yolk-shell structure, and nano-carbon material network, which can improve mass transfer and stabilize the structure, but also face problems such as complex preparation and high cost, making it difficult to truly commercialize. In order to further promote the industrialization and application of silicon-based negative electrode materials and improve the energy density of commercial lithium ion secondary batteries, it is currently important and difficult to develop silicon-based negative electrode materials with high energy density and long cycle life, which has great research significance and good application prospects. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a high-performance silicon-based composite negative electrode sheet and a preparation method thereof, which improves the performance of the negative electrode sheet containing a silicon-based active material in a lithium ion secondary battery by adding defective carbon nanotubes, uses the strong local stress generated by the silicon-based active material during the charging expansion stage to cause high strain on the defective carbon nanotubes, enhances the chemical activity of atoms at the defect sites, and thus generates a "stress-chemical interface coupling reaction" between lithium atoms and silicon-based clusters to in-situ anchor the silicon-based clusters to stabilize the cycle performance.

[0007] Further, the present application also provides the application of the high-performance silicon-based composite negative electrode sheet in the preparation of a lithium ion battery or a lithium ion secondary battery.

[0008] In order to achieve the above technical purpose, the present application adopts the following technical scheme:

[0009] A preparation method of a high-performance silicon-based composite negative electrode sheet, which uses single-walled carbon nanotubes containing defects, doped elements or functional group modifications to improve the silicon-based negative electrode, reconstructs the three-dimensional structure of the silicon-based negative electrode through mechanical-chemical interface coupling, and in-situ anchors the silicon-based clusters to improve the performance of the prepared silicon-based negative electrode sheet;

[0010] The preparation method specifically comprises the following steps:

[0011] Step 1: a certain amount of a surfactant and a certain amount of defective single-walled carbon nanotubes are dispersed in a solvent I by ultrasonic treatment, and then after removing the agglomerated particles by centrifugation, a dispersion liquid A which is stable and uniform in dispersion is obtained;

[0012] Step 2: the silicon-based active material, the binder, the carbon-based conductive agent and the dispersion liquid A in step 1 are mixed in a certain proportion by a wet mixing method to prepare a mixed slurry;

[0013] Step 3: the mixed slurry prepared in step 2 is coated on a conductive substrate, dried, cut, and the high-performance silicon-based composite negative electrode sheet is obtained.

[0014] Further, the surfactant in step 1 is one or more of carboxymethyl cellulose, polyvinylpyrrolidone, sodium dodecyl sulfate, cetyltrimethylammonium bromide and sodium lignosulfonate, and is preferably carboxymethyl cellulose.

[0015] Further, the defective single-walled carbon nanotubes in step 1 contain one or more of four-membered ring defects, five-membered ring defects, seven-membered ring defects and eight-membered ring defects in the molecular structure, or are doped with one or more of oxygen, fluorine, nitrogen, sulfur, selenium, boron, phosphorus, lithium and the like.

[0016] Further, the solvent I in step 1 is one or more of water, ethanol, N-methyl pyrrolidone, etc.

[0017] Further, the mass ratio of the defective single-walled carbon nanotubes to the surfactant in step 1 is (0.01-20):1.

[0018] Further, the mass ratio of the defective single-walled carbon nanotubes to the solvent I in step 1 is (0.001-1):1.

[0019] Further, the ultrasonic treatment in step 1 is performed at a temperature of -10-10°C for 1-3 hours using an ultrasonic disrupter or an ultrasonic cleaner, and the ultrasonic power is 100-2000 watts; further preferably, the ultrasonic treatment is performed in a manner of ultrasonic treatment for 2-3 seconds and then stopping for 2-3 seconds, and the ultrasonic treatment is performed for 1-3 hours.

[0020] Further, the centrifugal speed in step 1 is 500-4000 revolutions per minute, and the centrifugal time is 5-100 minutes.

[0021] Further, in step 2, the mass ratio of the silicon-based active material, the binder, the carbon-based conductive agent, and the defective single-walled carbon nanotubes is (0.1-96):(0.01-25):(0.01-25):(0.001-5).

[0022] Further, the silicon-based active material in step 2 is one or more of elemental silicon, silicon monoxide, and silicon-carbon composite material, or is a composite of one or more of elemental silicon, silicon monoxide, and silicon-carbon composite material and graphite.

[0023] Further, the silicon-based active material is preferably silicon monoxide SiO x , wherein the atomic ratio of silicon and oxygen in the silicon monoxide is 4:1-0.25:1; or the silicon-based active material is preferably silicon monoxide SiO x , wherein the atomic ratio of silicon in the silicon monoxide is 61%-64%, preferably 62.5%.

[0024] Alternatively, as another preferred technical solution, the silicon-based active material is preferably carbon-coated silicon monoxide, which is composed of silicon monoxide SiO x and a carbon coating layer obtained after carbonization of pitch, and the mass ratio of the silicon monoxide SiO x to the carbon coating layer is (3-9):1, preferably 8:2 or 9:1.

[0025] Further, the carbon-coated silicon monoxide is obtained by mixing silicon monoxide SiO x and pitch and then carbonizing at high temperature and annealing, and the specific preparation method is as follows: the silicon monoxide SiO xMixing with asphalt according to a certain mass ratio for 10-12 hours at a speed of 400-600 rpm, then softening at 300-330℃ for 1-2 hours under argon atmosphere, then carbonizing at 800-1000℃ for 2-3 hours, and then naturally cooling, to obtain the product.

[0026] Alternatively, as another preferred technical solution, the silicon-based active material is preferably a mixture of carbon-coated silicon suboxide and graphite, wherein the mass ratio of carbon-coated silicon suboxide to graphite is 1:(3-9), preferably 2:8 or 1:9.

[0027] Further, the binder in step 2 is one or more of carboxymethyl cellulose, sodium alginate, ammonium alginate, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid (PPA), lithium polyacrylic acid (lithium PPA), styrene butadiene rubber, and polystyrene butadiene copolymer.

[0028] Further preferably, the binder is a mixture of carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) in a mass ratio of 1:(1-2), preferably 1:1.

[0029] Further, the carbon-based conductive agent in step 2 is one or more of artificial graphite, natural graphite, hard carbon, soft carbon, acetylene black, Ketjen black, carbon black Super P, graphene, multi-walled carbon nanotubes, and fibrous carbon.

[0030] Further, in step 2, when wet mixing, a magnetic stirrer, a ball mill mixer, a swing mixer, a rotary mixer, a V-shaped mixer, or the like is used for stirring and mixing, the stirring time is 12-36 hours, and the rotation speed is 50-2000 rpm.

[0031] Further preferably, in step 2, when wet mixing, a solvent II can also be added, and the solvent II is one or more of water, ethanol, and N-methyl pyrrolidone.

[0032] Further, the conductive substrate in step 3 is any one of copper foil, carbon-coated copper foil, copper mesh, foamed copper, stainless steel, stainless steel mesh, carbon paper, and carbon cloth.

[0033] Further, in step 3, when mixing the slurry for coating, the loading amount of the mixed slurry is less than or equal to 1.2 mg / cm 2 .

[0034] Further, the drying method in step 3 is drying in a drum drying oven, a vacuum drying oven, or a box furnace, the drying temperature is 50-120℃, and the drying time is 12-36 hours; preferably, when vacuum drying is performed using a vacuum drying oven, the vacuum degree is ≤133 Pa.

[0035] Further, the application also provides a high-performance silicon-based composite negative electrode sheet prepared by the above method, which has good initial efficiency, rate performance and cycle stability and can be used to prepare a lithium ion battery.

[0036] Further, based on a general inventive concept, the application also provides application of the high-performance silicon-based composite negative electrode sheet in preparation of a lithium ion battery or a lithium ion secondary battery.

[0037] Further, based on a general inventive concept, the application also provides a method for preparing a lithium ion battery or a lithium ion secondary battery by using the high-performance silicon-based composite negative electrode sheet, comprising the following steps:

[0038] a) electrode sheet preparation: using a puncher or a slicer to prepare the high-performance silicon-based composite negative electrode sheet into a button electrode wafer;

[0039] b) button cell assembly: using a lithium sheet as a counter electrode, assembling the electrode wafer prepared in step a), the lithium sheet (as a counter electrode), a separator and an electrolyte into a button cell, and the cell model is a CR2032 type button cell.

[0040] Specifically, the diameter of the electrode wafer in step a) is 12 mm.

[0041] Specifically, in the cell assembled in step b), the separator type is a separator Celgard2400, and the electrolyte is 1M LiPF6 / EC+DMC (V / V=1:1) added with 5% fluoroethylene carbonate FEC.

[0042] Further, based on a general inventive concept, the application also provides a lithium ion battery or a lithium ion secondary battery prepared by the above method.

[0043] Compared with the prior art, the application has the following advantages:

[0044] 1. The application provides a preparation method of a high-performance silicon-based composite negative electrode sheet, which is simple to operate, has remarkable effect and is easy to scale up, has high commercial value and is easy to scale up.

[0045] 2. The application can improve the performance of a negative electrode sheet containing a silicon-based active material in a lithium ion secondary battery by adding defective carbon nanotubes, use strong local stress generated by the silicon-based active material in the charging expansion stage to cause high strain on the defective carbon nanotubes, enhance the chemical activity of atoms at the defect sites, thereby generating a "stress-chemical interface coupling reaction" between the silicon-based clusters and lithium atoms, in-situ anchoring the silicon-based clusters, avoiding loss of electrical contact, and at the same time, the silicon-based clusters can also separate the defective carbon nanotube bundles, enhancing the transmission rate of lithium ions.

[0046] The application can reconfigure the three-dimensional structure in the silicon-based negative electrode by using the stress-chemical interface coupling effect, thereby stabilizing the electrode structure and promoting mass transfer, and effectively improving the rate and cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 SEM morphology of the high-performance silicon-based composite negative electrode prepared in Example 1 after cycling;

[0048] Figure 2 TEM morphology of the defective carbon nanotubes of the high-performance silicon-based composite negative electrode prepared in Example 1 after cycling;

[0049] Figure 3 Cycle performance chart of Example 1, 2 and Comparative Example 1, 2 of the application;

[0050] Figure 4 Cycle performance chart of Example 3 of the application;

[0051] Figure 5 Cycle performance chart of Example 4, 5 of the application;

[0052] Figure 6 Cycle performance chart of Example 2, 6, 7 of the application;

[0053] Figure 7 Cycle performance chart of Example 8 of the application. DETAILED DESCRIPTION

[0054] The technical solutions in the application will be described clearly and completely below in combination with the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0055] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods; unless otherwise specified, the reagents, raw materials, etc. used in the following examples are conventional commercially available products and can be obtained through commercial channels.

[0056] The silicon monoxide SiO used in the following examples and comparative examples is x It is a powder produced by Shanghai Liangtian Nanometer Material Co., Ltd., with a product number of XT-SIO-5U, a median particle size D50 of 5 μm, and a silicon atomic percentage of 62.5%.

[0057] Example 1

[0058] Example 1 provides a preparation method of a high-performance silicon-based composite negative electrode, and the specific steps are as follows:

[0059] Step 1: 10 g of surfactant (carboxymethyl cellulose) and 5 g of single-walled carbon nanotubes with five-membered ring and seven-membered ring defects (preparation method reference literature Wang, Haolin, et al. "What Is the Real Origin of Single-Walled Carbon Nanotubes for the Performance Enhancement of Si-Based Anodes?." Journal of the American Chemical Society 2024, 146(25), 17041-17053) were added to 85 g of ultrapure water, and then placed in an ultrasonic crusher under the condition of ultrasonic power of 1500 watts and water bath of 0 ℃, and ultrasonic treatment was carried out for 2 hours with the program of 3 seconds of ultrasonic and 3 seconds of stop, and after centrifugation at 2000 rpm for 30 minutes, the supernatant was taken as the dispersion liquid A of the defect single-walled carbon nanotubes which was stable and uniform in dispersion;

[0060] Step 2: Take silicon monoxide SiO x , binder (CMC + SBR), carbon black Super P (carbon-based conductive agent, purchased from Shenzhen Kexin Zhida Technology Co., Ltd., brand CAS 1333-86-4) and defect single-walled carbon nanotube dispersion liquid A in step 1 were wet mixed, and the obtained mixture was stirred on the stirring table of a magnetic stirrer at a speed of 400 revolutions for 24 hours to prepare a slurry;

[0061] Among them, the mass ratio of silicon monoxide SiO x , binder, carbon-based conductive agent and single-walled carbon nanotube with five-membered ring and seven-membered ring defects is 90:5:4:1; the mass ratio of CMC and SBR in the binder is 1:1;

[0062] Step 3: The slurry of step 2 was uniformly coated onto the surface of the copper foil using a coating machine, and the loading amount of the slurry was about 1.2 mg / cm 2 After drying in a vacuum drying oven (vacuum degree ≤133 Pa) at 60 ℃ for 24 hours, cutting was carried out to obtain the high-performance silicon-based composite negative electrode sheet.

[0063] The surface morphology of the high-performance silicon-based composite negative electrode sheet prepared in Example 1 was characterized by scanning electron microscopy, and the obtained SEM image is shown in Figure 1 The morphology of the defect carbon nanotubes after the negative electrode sheet in Example 1 was cycled was characterized by transmission electron microscopy, and the obtained TEM image is shown in Figure 2 From Figure 1 and Figure 2 , it can be seen that the pulverized silicon-based particles are anchored on the surface of the defect single-walled carbon nanotubes.

[0064] Example 2

[0065] Example 2 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Example 2 is different from that of Example 1 in that:

[0066] In step 2, the silicon monoxide SiO x , the binder, the carbon-based conductive agent, and the single-walled carbon nanotube with five-membered ring and seven-membered ring defects have a mass ratio of 90:5:3:2, and the other steps and conditions are the same as those of Example 1.

[0067] Example 3

[0068] Example 3 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Example 3 is different from that of Example 1 in that:

[0069] In step 2, the silicon monoxide SiO x used is replaced by carbon-coated silicon suboxide, and the other steps and conditions are the same as those of Example 1. The carbon-coated silicon suboxide is composed of a carbon coating layer formed by silicon monoxide SiO x and pitch carbonization, and the mass ratio of SiO x to the carbon coating layer in the carbon-coated silicon suboxide is 8:2.

[0070] The carbon-coated silicon suboxide is obtained by mixing silicon monoxide SiO x and pitch and then carbonizing and annealing under high temperature. The specific preparation method is as follows: using a mixer, silicon monoxide SiO x and pitch are mixed at a mass ratio of 8:2 at a speed of 500 rmp for 12 h, then softened at 310°C for 2 h under an argon atmosphere, then carbonized at 900°C for 2 h, and naturally cooled.

[0071] Example 4

[0072] Example 4 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Example 4 is different from that of Example 1 in that:

[0073] In step 2, the silicon monoxide SiO x used is replaced by a mixture of carbon-coated silicon suboxide and artificial graphite (purchased from Koda New Material Co., Ltd., product model KD-1), and the other steps and conditions are the same as those of Example 1.

[0074] The mass ratio of the carbon-coated silicon suboxide to the artificial graphite is 2:8. The carbon-coated silicon suboxide is composed of a carbon coating layer formed by silicon monoxide SiO x and pitch carbonization, and the mass ratio of SiO xThe mass ratio of the carbon-coated layer to the carbon-coated silicon is 8:2, and the specific preparation method of the carbon-coated silicon is the same as that in Embodiment 3.

[0075] Embodiment 5

[0076] Embodiment 5 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Embodiment 5 is different from that of Embodiment 1 in that:

[0077] In step 2, the silicon monoxide SiO used is replaced by a mixture of carbon-coated silicon and artificial graphite (purchased from Koda New Materials Co., Ltd., product model KD-1), and other steps and conditions are the same as those in Embodiment 1. x

[0078] The mass ratio of the carbon-coated silicon to the artificial graphite is 1:9; the carbon-coated silicon is composed of a carbon-coated layer formed by silicon monoxide SiO x and pitch carbonization, and the mass ratio of SiO x in the carbon-coated silicon to the carbon-coated layer is 8:2, and the specific preparation method of the carbon-coated silicon is the same as that in Embodiment 3.

[0079] Embodiment 6

[0080] Embodiment 6 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Embodiment 6 is different from that of Embodiment 2 in that:

[0081] In step 2, the binder used is replaced by polyacrylic acid (PAA, purchased from Dongguan Keluode New Energy Technology Co., Ltd., item number MA-EN-BI-0015), and other steps and conditions are the same as those in Embodiment 2.

[0082] Embodiment 7

[0083] Embodiment 7 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Embodiment 7 is different from that of Embodiment 2 in that:

[0084] In step 2, the binder used is replaced by lithiumated polyacrylic acid (lithiated PAA) (PAA-Li, purchased from Dongguan Keluode New Energy Technology Co., Ltd., item number MA-EN-BI-0013), and other steps and conditions are the same as those in Embodiment 2.

[0085] Embodiment 8

[0086] Embodiment 8 provides a preparation method of a high-performance silicon-based composite negative electrode sheet. The preparation method of Embodiment 8 is different from that of Embodiment 2 in that:

[0087] ​The binder used in step 2 was replaced with sodium alginate (purchased from Dongguan Keluode New Energy Technology Co., Ltd., product number MA-EN-BI-0006), and the other steps and conditions were the same as in Example 2.

[0088] Comparative Example 1

[0089] The defective single-walled carbon nanotubes used in step 1 of Example 1 were replaced with multi-walled carbon nanotubes (purchased from Jiangsu Xianfeng Nanometer Material Technology Co., Ltd., product number XFM19, length 20-30 μm), and the other steps and conditions were the same as in Example 1.

[0090] Comparative Example 2

[0091] Step 1: Take silicon monoxide SiO x , binder (CMC + SBR), and carbon black Super P (carbon-based conductive agent, purchased from Shenzhen Kejing Zhida Technology Co., Ltd., product number CAS 1333-86-4), and mix them in a wet manner. The resulting mixture was stirred on a magnetic stirring table at a speed of 400 revolutions for 24 hours to prepare a slurry;

[0092] The mass ratio of silicon monoxide SiO x , binder (CMC + SBR), and carbon black Super P was 90:5:5; the mass ratio of CMC and SBR in the binder was 1:1;

[0093] Step 2: The slurry of step 2 was uniformly coated onto the surface of the copper foil using a coating machine, and the loading amount of the slurry was about 1.2 mg / cm 2 After drying in a vacuum oven (vacuum degree ≤133 Pa) at 60°C for 24 hours, the silicon-based negative electrode sheet of Comparative Example 2 was obtained.

[0094] Performance Test

[0095] The products prepared in Examples 1-8 and Comparative Examples 1-2 were assembled into batteries and subjected to electrochemical performance testing (test method reference: Wang, Haolin, et al. "What Is the Real Origin of Single-Walled Carbon Nanotubes for the Performance Enhancement of Si-Based Anodes?." Journal of the American Chemical Society 2024, 146(25), 17041-17053), with the specific method steps being:

[0096] a) Preparation of electrode sheet: the negative electrode sheet prepared in Examples 1-8 and Comparative Examples 1-2 was punched into a 12mm diameter button electrode round sheet using a puncher or a slicer;

[0097] b) Button cell assembly and performance test: the electrode round sheet prepared in step a), a lithium metal sheet (as a counter electrode), a separator, and an electrolyte were assembled into a button cell using a CR2032 type button cell model, a lithium metal sheet as a counter electrode, a separator type of Celgard 2400, and an electrolyte of 1M LiPF6 / EC+DMC (V / V=1:1) with 5% fluoroethylene carbonate FEC added, which was purchased from Suzhou Duoduo Chemical Technology Co., Ltd. with a product code of LB-007.

[0098] The cycle performance test was performed under the following conditions: after 3 cycles of activation at 0.05A / g or 0.1A / g, constant current charge-discharge cycles were performed at a current density of 0.5A / g or 1A / g, and the charge-discharge voltage was limited to 0.01-2V.

[0099] The cycle performance of the high-performance silicon-based composite negative electrode sheet prepared in Examples 1-8 and the silicon-based negative electrode sheet of Comparative Examples 1-2 was detected according to the above battery assembly and test method, and the performance comparison chart is shown in Figures 3-7 , and the capacity, coulombic efficiency, and capacity retention rate are shown in Table 1.

[0100] Table 1

[0101]

[0102] As can be seen from Table 1, the coulombic efficiency of the silicon-based negative electrode sheet after adding the single-walled carbon nanotube with five-membered ring and seven-membered ring defects is significantly improved, from less than 50% in the comparative example to more than 78.5%; at the same time, the long cycle stability is also greatly improved, and the capacity retention rate is greatly improved, which significantly proves the role of the defective single-walled carbon nanotube in improving the performance of the silicon-based negative electrode sheet.

[0103] In summary, the high-performance silicon-based composite negative electrode sheet prepared by the present application can improve the performance of the negative electrode sheet containing silicon-based active material in lithium ion batteries or lithium ion secondary batteries by adding defective carbon nanotubes, and the strong local stress generated by the silicon-based material during the charging expansion stage causes high strain on the defective carbon nanotubes, enhances the chemical activity of atoms at the defect sites, and generates a "stress-chemical interface coupling effect" between lithium atoms and silicon-based clusters, which in-situ anchors the silicon-based clusters and avoids the loss of electrical contact. At the same time, the silicon-based clusters can also separate the defective carbon nanotube bundles, enhancing the transmission rate of lithium ions.

[0104] The application can reconfigure the three-dimensional structure in the silicon-based negative electrode by using "stress-chemical interface coupling", thereby stabilizing the electrode structure and promoting mass transfer, and effectively improving the rate and cycle performance.

[0105] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance silicon-based composite negative electrode, characterized in that, Includes the following steps: Step 1: Disperse a certain amount of surfactant and a certain amount of defective single-walled carbon nanotubes in solvent I by ultrasonic treatment, and then centrifuge to obtain a stable and uniform dispersion A. Step 2: Prepare a mixed slurry by mixing silicon-based active material, binder, carbon-based conductive agent and dispersion A from Step 1 in a certain proportion using a wet mixing method; Step 3: Coat the mixed slurry prepared in step 2 onto a conductive substrate, dry it, and cut it to obtain the high-performance silicon-based composite negative electrode sheet.

2. The preparation method according to claim 1, characterized in that, The surfactant mentioned in step 1 is one or more of carboxymethyl cellulose, polyvinylpyrrolidone, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and sodium lignosulfonate; the solvent I mentioned in step 1 is one or more of water, ethanol, and N-methylpyrrolidone.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the defective single-walled carbon nanotubes to the surfactant in step 1 is (0.01~20):1; the mass ratio of the defective single-walled carbon nanotubes to solvent I in step 1 is (0.001~1):

1.

4. The preparation method according to claim 1, characterized in that, The ultrasonic treatment method described in step 1 is to treat at a temperature of -10~10℃ for 1~3 hours; the ultrasonic power is 100~2000 watts.

5. The preparation method according to claim 1, characterized in that, In step 2, the mass ratio of silicon-based active material, binder, carbon-based conductive agent and defective single-walled carbon nanotubes is (0.1-96):(0.01-25):(0.01-25):(0.001-5).

6. The preparation method according to claim 1, characterized in that, The silicon-based active material mentioned in step 2 is one or more of elemental silicon, silicon suboxide, and silicon-carbon composite materials, or a composite of one or more of elemental silicon, silicon suboxide, and silicon-carbon composite materials with graphite; The adhesive mentioned in step 2 is one or more of the following: carboxymethyl cellulose, sodium alginate, ammonium alginate, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, lithium-ionized polyacrylic acid, styrene-butadiene rubber, and polystyrene-butadiene copolymer. The carbon-based conductive agent mentioned in step 2 is one or more of the following: artificial graphite, natural graphite, hard carbon, soft carbon, acetylene black, Ketjen black, carbon black SuperP, graphene, multi-walled carbon nanotubes, and fibrous carbon.

7. The preparation method according to claim 1, characterized in that, The conductive substrate mentioned in step 3 is any one of copper foil, carbon-coated copper foil, copper mesh, copper foam, stainless steel, stainless steel mesh, carbon paper, and carbon cloth.

8. A high-performance silicon-based composite negative electrode sheet prepared by any one of the methods described in claims 1-7.

9. The application of the high-performance silicon-based composite negative electrode sheet according to claim 8 in the preparation of lithium-ion batteries or lithium-ion secondary batteries.

10. A method for preparing a lithium-ion battery or a lithium-ion secondary battery using the high-performance silicon-based composite negative electrode sheet as described in claim 8, comprising the following steps: a) Preparation of electrode sheet: The high-performance silicon-based composite negative electrode sheet is made into a button-type electrode disc; b) Button cell assembly: Using a lithium metal sheet as the counter electrode, the electrode disc, lithium metal sheet, separator, and electrolyte prepared in step a) are assembled into a button cell. The battery model is a CR2032 type button cell.

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