Silicon-based negative electrode sheet, method for manufacturing the same, and lithium ion battery

Abstract

The present invention provides a silicon-based negative electrode sheet, a method for manufacturing the same, and a lithium-ion battery. Such a silicon-based negative electrode sheet has a porous current collector and a silicon-containing material adhered in the voids of the porous current collector, and the porous current collector is a porous carbon material. On the one hand, due to the network structure of the porous carbon material itself, the resistivity of the silicon-based negative electrode sheet is extremely reduced, the toughness of the silicon-based negative electrode sheet is enhanced, and further expansion of the silicon-based negative electrode sheet is effectively prevented. On the other hand, due to the network structure of the porous carbon material itself, the particle surface of the silicon-carbon material is coated, and a highly conductive, robust and permanent connection is established between the silicon particles. In addition, the porous carbon material has advantages such as low density, low cost, and corrosion resistance compared to a metal current collector. Therefore, by using the porous carbon material as the negative electrode current collector, while reducing the content of the conductive agent in the silicon-based negative electrode sheet, the mixing ratio of the silicon-carbon material in the entire silicon-based negative electrode sheet can be improved, and the energy density of the electric core can be further improved.

Description

Technical Field

[0001] This application is based on and claims priority to a Chinese application with Chinese Application No. 202211625901.0 and a filing date of December 16, 2022, and the content disclosed in the Chinese application is hereby incorporated by reference in its entirety into this application.

[0002] The present invention relates to the technical field of lithium-ion batteries, and specifically to a silicon-based negative electrode sheet, a method for manufacturing the same, and a lithium-ion battery.

Background Art

[0003] The improvement of battery energy density mainly depends on the development of key electrode materials, such as the continuous increase in the capacity of positive and negative electrode materials. The capacity of existing lithium battery negative electrode materials is approaching its limit. Taking graphite-based negative electrodes (with a proportion as high as 98% of lithium battery negative electrode materials) as an example, the specific capacity of graphite-based negative electrodes is all above 350 mAh / g and is approaching the upper limit value of the theoretical specific capacity of 372 mAh / g. Therefore, in order to meet the energy demands of the new generation, the development of new types of lithium battery negative electrodes is an urgent task to improve the battery energy density.

[0004] Currently, the advantages of silicon-based negative electrodes are obvious. Its theoretical specific capacity reaches up to 4200 mAh / g, which is more than 10 times that of graphite materials. Moreover, silicon-based negative electrodes provide paths for the insertion and extraction of lithium ions from various directions, have excellent fast charging performance, and are the future development direction of negative electrodes. However, silicon-based negative electrodes have serious volume expansion during the lithium insertion process, poor conductivity of the material, and their commercial application is restricted due to problems such as first-cycle efficiency and cycle performance.

Summary of the Invention

[0005] The main objective of the present invention is to provide a silicon-based negative electrode sheet, a method for manufacturing the same, and a lithium-ion battery to solve the serious problem of volume expansion of silicon-based negative electrodes in the prior art.

[0006] In order to achieve the above object, according to one aspect of the present invention, a silicon-based negative electrode sheet is proposed, which has a porous current collector and a silicon-containing material attached in the voids of the porous current collector, and the porous current collector is a porous carbon material.

[0007] Furthermore, the porosity of the above-mentioned porous current collector is 50 to 90%, preferably, the pore diameter of the porous current collector is 50 to 100 μm, and more preferably, the porous current collector is any one or more selected from carbon fibers, carbon fiber cloth, carbon nanotubes, and foam carbon.

[0008] Furthermore, the above-mentioned silicon-based negative electrode sheet further has a functional auxiliary agent for adhering the porous current collector and the silicon-containing material. Preferably, the mass ratio of the porous current collector to the silicon-containing material is 5 to 15:100. Preferably, the mass of the functional auxiliary agent is 0.2 to 5% of the silicon-containing material. Preferably, the silicon-containing material is any one or more selected from silicon dioxide, silicon carbide, micrometer silicon, nanometer silicon, silicon oxide modified by pre-doping with lithium, and a mixture in which graphite and silicon oxide are mixed. More preferably, the silicon-containing material is a mixture in which graphite and silicon oxide are mixed. Preferably, the mass ratio of silicon oxide to graphite in the mixture is 1:1 to 4. Preferably, the functional auxiliary agent is a dopamine monomer.

[0009] Furthermore, the thickness of the above-mentioned silicon-based negative electrode sheet is 6 to 200 μm. Preferably, the silicon-based negative electrode sheet further has an adhesive and a conductive agent. Preferably, the adhesive is any one or more selected from styrene-butadiene rubber, sodium carboxymethyl cellulose, and polyvinyl alcohol. Preferably, the conductive agent is any one or more selected from carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene.

[0010] According to another aspect of the present invention, there is provided a method for manufacturing the above silicon-based negative electrode sheet, including: Step S1: obtaining an active current collector by applying a negative electrode slurry containing a silicon-containing material onto the surface of a porous current collector; and Step S2: obtaining a silicon-based negative electrode sheet by drying, roll pressing, and sheet punching the active current collector.

[0011] Furthermore, the above Step S1 includes a surface modification treatment on the porous current collector. Preferably, the process of the surface modification treatment includes: Step S11: obtaining an oxidized current collector by oxidizing the porous current collector with an oxidant solution; Step S12: obtaining a washed current collector by washing the oxidized current collector; and Step S13: obtaining a modified porous current collector by immersing the washed current collector in a functional auxiliary agent solution. The oxidant solution is a nitric acid solution with a concentration of 50-90 wt%. Preferably, the oxidation treatment time is 20-60 min. Preferably, the residual amount of NO in the washed current collector is less than 50 ppm. Preferably, the functional auxiliary agent solution is a dopamine monomer solution. Preferably, the concentration of the dopamine monomer solution is 2-3 g / L. Preferably, the solvent in the dopamine monomer solution is a Tris-HCl buffer solution. Preferably, the immersion time is 10-24 h. 3 - Furthermore, in the above Step S1, coating is simultaneously performed on the opposing surfaces of the porous current collector. Preferably, the advancing speed of the coating is 10-50 m / min. Preferably, the solid content of the negative electrode slurry is 35-50 wt%. Preferably, the viscosity of the negative electrode slurry is 3000-7000 mPa·s.

[0012] in it. -1 is.

[0013] Furthermore, in the above Step S2, the drying temperature is 60-150°C.

[0014] According to still another aspect of the present invention, there is provided a lithium-ion battery having a positive electrode sheet, an electrolyte, and a negative electrode sheet, wherein the negative electrode sheet is the above-described silicon-based negative electrode sheet.

[0015] Furthermore, the porous current collector of the silicon-based negative electrode sheet and the metal wire of the lithium-ion battery are connected by a metal crimping sleeve.

[0016] By applying the technical solution of the present invention, on the one hand, due to the network structure of the porous carbon material itself, the resistivity of the silicon-based negative electrode sheet is extremely reduced, the toughness of the silicon-based negative electrode sheet is enhanced, and further the expansion of the silicon-based negative electrode sheet is effectively prevented. On the other hand, due to the network structure of the porous carbon material itself, the particle surface of the silicon-carbon material is coated, and a highly conductive, robust and permanent connection is established between the silicon particles. Even when the volume expansion of the silicon particles occurs and cracks begin to occur, the porous carbon material can maintain a good connection between the silicon particles, thereby preventing the rupture of the silicon-carbon material, and at the same time bringing high capacity to the lithium-ion battery, and also achieving excellent electrical performances such as cycle stability and initial efficiency.

[0017] In addition, the porous carbon material has advantages such as low density, low cost, and corrosion resistance compared with a metal current collector. Therefore, by using the porous carbon material as the negative electrode current collector, while reducing the content of the conductive agent in the silicon-based negative electrode sheet, the mixing ratio of the silicon-carbon material in the entire silicon-based negative electrode sheet can be improved, and the energy density of the electric core can be further improved.

Brief Description of the Drawings

[0018] The drawings of the specification constituting a part of the present application are for providing a further understanding of the present invention, and the exemplary embodiments and descriptions thereof of the present invention are for explaining the present invention and do not unduly limit the present invention. The drawings are as follows.

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0019] Particularly, it should be noted that on the premise of no contradiction, the embodiments in the present application and the features mentioned in the embodiments can be combined with each other. Hereinafter, the present invention will be described in detail in combination with embodiments with reference to the drawings.

[0020] As analyzed in the background art part of the present application, the conventional technology has a serious problem of volume expansion of the silicon-based negative electrode. In order to solve this problem, the present application provides a silicon-based negative electrode sheet, its manufacturing method, and a lithium-ion battery.

[0021] In a typical embodiment according to the present application, a silicon-based negative electrode sheet is provided, which has a porous current collector and a silicon-containing material attached in the voids of the porous current collector, and the porous current collector is a porous carbon material.

[0022] According to the silicon-based negative electrode sheet of the present application, on the one hand, the resistivity of the silicon-based negative electrode sheet is extremely greatly reduced by the network structure of the porous carbon material itself, the toughness of the silicon-based negative electrode sheet is enhanced, and further the expansion of the silicon-based negative electrode sheet is effectively prevented.

[0023] On the other hand, the particle surface of the silicon-containing material is coated by the network structure of the porous carbon material itself, and a highly conductive, robust and permanent connection is established between silicon particles. Even when volume expansion and cracks begin to occur in the silicon particles, the porous carbon material can maintain a good connection between the silicon particles, thereby preventing the rupture of the silicon-containing material, and at the same time bringing high capacity to the lithium-ion battery, and can also achieve excellent electrical performances such as cycle stability and initial efficiency.

[0024] In addition, the porous carbon material has advantages such as low density, low cost, and corrosion resistance compared with metal current collectors. Therefore, by using the porous carbon material as the negative electrode current collector, while reducing the content of the conductive agent in the silicon-based negative electrode sheet, the mixing ratio of the silicon-containing material in the entire silicon-based negative electrode sheet can be improved, and the energy density of the electric core can be further improved.

[0025] In order to enhance the penetration efficiency and effect of the silicon-containing material in the voids of the porous current collector, the porosity of the above-mentioned porous current collector is preferably 50-90%, the pore diameter of the porous current collector is preferably 50-100 μm, and further, the porous current collector is preferably any one or more selected from carbon fibers, carbon fiber cloth, carbon nanotubes, and foamed carbon.

[0026] In one embodiment of the present application, the above silicon-based negative electrode sheet further has a functional aid for adhering the porous current collector and the silicon-containing material, and the mass ratio of the porous current collector to the silicon-containing material is preferably 5 to 15:100, and the mass of the functional aid is preferably 0.2 to 5% of the silicon-containing material. The silicon-containing material is preferably any one or more selected from silicon dioxide, silicon carbide, micrometer silicon, nanometer silicon, silicon oxide modified by pre-doping with lithium, and a mixture in which graphite and silicon oxide are mixed. More preferably, the silicon-containing material is a mixture in which graphite and silicon oxide are mixed. The mass ratio of silicon oxide to graphite in the mixture is preferably 1:1 to 4. The functional aid is preferably dopamine monomer.

[0027] The functional aid is advantageous for enhancing the penetration degree of the negative electrode slurry in the pores of the porous current collector while better adhering the negative electrode slurry, especially the silicon-carbon material therein, to the pores of the porous current collector. The types of suitable silicon-containing materials and functional aids, as well as the mass ratios of the suitable porous current collector, silicon-containing material, and functional aid, and the functional aid can realize strong adhesion of the silicon-containing material to the porous current collector, and at the same time, increase the proportion of the silicon-containing material in the negative electrode sheet having the same mass as much as possible, which is helpful for improving electrical performance such as the capacity of the lithium-ion battery.

[0028] In one embodiment of the present application, the thickness of the above silicon-based negative electrode sheet is 6 to 200 μm. Preferably, the silicon-based negative electrode sheet further has an adhesive and a conductive agent. Preferably, the adhesive is any one or more selected from styrene-butadiene rubber, sodium carboxymethyl cellulose, and polyvinyl alcohol. Preferably, the conductive agent is any one or more selected from carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene.

[0029] For a current collector having the same thickness, the technical solution of applying the negative electrode slurry to the surface of the porous current collector helps to reduce the thickness of the silicon-based negative electrode sheet. Preferably, the thickness of the silicon-based negative electrode sheet is within the above range, thereby helping to manufacture a silicon-based negative electrode sheet with a thinner thickness, higher magnification, and higher energy density. The adhesive is advantageous for enhancing the adhesion effect between each component and the porous current collector, and the conductive agent is advantageous for enhancing the conductivity of the entire silicon-based negative electrode sheet. Suitable types of adhesives and conductive agents exert their respective advantages and help to perform better synergistic effects among the components, thereby obtaining a lithium-ion battery with excellent comprehensive electrical performance.

[0030] In another typical embodiment of the present application, there is provided a method for manufacturing the above silicon-based negative electrode sheet, including: Step S1: obtaining an active current collector by applying a negative electrode slurry containing a silicon-containing material to the surface of a porous current collector; and Step S2: obtaining a silicon-based negative electrode sheet by drying, roll-pressing, and sheet punching the active current collector.

[0031] According to the above manufacturing method, on the one hand, due to the network structure of the porous carbon material itself, the resistivity of the silicon-based negative electrode sheet is extremely greatly reduced, the toughness of the silicon-based negative electrode sheet is enhanced, and further expansion of the silicon-based negative electrode sheet is effectively prevented. On the other hand, due to the network structure of the porous carbon material itself, the particle surface of the silicon-containing material is coated, and a highly conductive, firm, and permanent connection is established between the silicon particles. Even when volume expansion and cracks begin to occur in the silicon particles, the porous carbon material can maintain a good connection between the silicon particles, thereby preventing the rupture of the silicon-containing material, and at the same time bringing high capacity to the lithium-ion battery, and also achieving excellent electrical performances such as cycle stability and initial efficiency.

[0032] In addition, the porous carbon material has advantages such as lower density, lower cost, and corrosion resistance compared to metal current collectors. Therefore, by using the porous carbon material as the negative electrode current collector, while reducing the content of the conductive agent in the silicon-based negative electrode sheet, the mixing ratio of the silicon-containing material in the entire silicon-based negative electrode sheet can be improved, and the energy density of the electric core can be further improved. Moreover, the above manufacturing method is simple and industrial production is easy.

[0033] The above method for applying the negative electrode slurry may be an ordinary coating method in conventional technologies such as extrusion coating, and will not be further described here.

[0034] In order to enhance the uniformity of the negative electrode slurry, preferably, first, the silicon-carbon material and the conductive agent are dry mixed. However, the stirring speed of the suitable dry mixing is 20 - 40 r / min, and the time is 20 - 50 min. Next, the adhesive is added. However, the kneading and stirring speed is 20 - 50 r / min, and the dispersion rotation speed is controlled at 40 - 100 r / min, the dispersion disk is at 3000 - 5000 r / min, and the dispersion time is 3 - 5 h for dispersion. After uniform dispersion, water is added in the remaining amount, and the obtained slurry is stirred and sieved to produce the negative electrode slurry.

[0035] In some embodiments of the present application, the above step S1 includes a surface modification treatment on the porous current collector. Preferably, the process of the surface modification treatment includes step S11: obtaining an oxidized current collector by oxidizing the porous current collector with an oxidant solution; step S12: obtaining the washed current collector by washing the oxidized current collector; and step S13: obtaining the modified porous current collector by immersing the washed current collector in a functional auxiliary agent solution. The oxidant solution is a nitric acid solution with a concentration of 50 - 90 wt%. Preferably, the oxidation treatment time is 20 - 60 min. Preferably, the NO in the washed current collector 3 -The residual amount is less than 50 ppm. Preferably, the functional auxiliary agent solution is a dopamine monomer solution. Preferably, the concentration of the dopamine monomer solution is 2 - 3 g / L. Preferably, the solvent in the dopamine monomer solution is a Tris-HCl buffer solution. Preferably, the immersion time is 10 - 24 h.

[0036] Performing the above-mentioned modification treatment on the surface of the porous current collector changes the performance such as the roughness of the surface of the porous current collector and the groups contained on the surface, increases the probability that the negative electrode slurry penetrates into its voids through the surface of the porous current collector, and is further advantageous for mixing the negative electrode slurry containing the silicon-carbon material into the interior of the porous current collector.

[0037] By oxidizing the porous current collector with an oxidizing agent solution, active groups such as carboxyl groups and hydroxyl groups can be generated on its surface, and moreover, the amount of these groups increases with the extension of the oxidation time and the increase in temperature. The oxidation treatment time is preferably 20 - 60 min. Thereby, the various oxygen-containing polar groups and grooves contained on the surface of the obtained porous current collector are significantly increased, which is advantageous for improving the bonding force between the porous current collector and the negative electrode slurry, and further helps the negative electrode slurry to penetrate into the voids of the porous current collector.

[0038] If the concentration of the nitric acid solution is too low, it is disadvantageous for improving the oxidation treatment efficiency. On the other hand, if the concentration of the nitric acid solution is too high, the porous current collector will be corroded by the strong acid during the oxidation process, causing a large loss in the strength of the porous current collector and affecting its performance. The oxidizing agent solution is preferably a nitric acid solution with a concentration of 50 - 90 wt%. The NO in the carbon material after washing 3 - The residual amount is preferably less than 50 ppm, thereby being advantageous for reducing the influence of NO 3 - on the performance of the silicon-based negative electrode sheet.

[0039] The immersion time is preferably 10 - 24 h, which is advantageous for more sufficiently adsorbing the functional auxiliary agent on the current collector after washing.

[0040] In order to prevent the negative electrode slurry from leaking from the pores of the porous current collector during the coating process, in the above step S1, it is preferable that the coating is simultaneously performed on the opposing surfaces of the porous current collector. The preferable progress speed of the coating is 10 to 50 m / min, which is advantageous for achieving both coating efficiency and coating effect. Whether the negative electrode slurry is too thin or too thick is disadvantageous for the coating of the negative electrode slurry. The preferable solid content of the negative electrode slurry is 35 to 50 wt%, and the viscosity of the negative electrode slurry is preferably 3000 to 7000 mPa·s -1 is preferable, which is advantageous for performing the coating more smoothly and reducing the working load of subsequent drying as much as possible, and is more advantageous for the adhesion of the negative electrode slurry into the porous current collector.

[0041] In order to enhance the efficiency and effect of drying while saving energy as much as possible, in the above step S2, the drying temperature is preferably 60 to 150°C.

[0042] In still another typical embodiment of the present application, a lithium-ion battery having a positive electrode sheet, an electrolyte, and a negative electrode sheet is proposed, wherein such a negative electrode sheet is the above-mentioned silicon-based negative electrode sheet.

[0043] The lithium-ion battery including the silicon-based negative electrode sheet according to the present application has electrical performances such as relatively high capacity, excellent cycle stability, and initial efficiency.

[0044] The above-mentioned porous current collector is a non-metallic material. In order to better fuse the silicon-based negative electrode sheet and the metal wire, it is preferable to connect the porous current collector of the above-mentioned silicon-based negative electrode sheet and the metal wire of the lithium-ion battery with a metal crimping sleeve. Preferably, by realizing a tighter connection between the silicon-based negative electrode sheet and the metal wire under a pressure of 50 to 1000 MPa, the reliability of the lithium-ion battery can be improved. In addition, since the porous current collector according to the present application has strong thermal conductivity, heat dissipation at the joint between the silicon-based negative electrode sheet and the metal wire is fast, and its service life is further improved.

[0045] Hereinafter, the beneficial effects of the present application will be further described in combination with examples.

[0046] Example 1 10 parts by weight of carbon fiber TGP-H-60 was oxidized with 60 wt% nitric acid for 30 min to obtain oxidized carbon fiber. The oxidizing agent remaining on the oxidized carbon fiber was removed by washing with water, and after washing 8 times, the residual amount of NO 3 - was 40 ppm, and the carbon fiber after washing was obtained in this way. The carbon fiber after washing was immersed in a dopamine monomer buffer solution (with a concentration of 2 g / L and containing 3 parts by weight of dopamine monomer) for 24 h to obtain modified carbon fiber. The modified carbon fiber had a porosity of 80% and a pore diameter of 50 to 95 μm. The SEM diagram of the modified carbon fiber is shown in Figure 1.

[0047] The specific mixing process is as follows: First, 25 parts by weight of silicon oxide SiO, 75 parts by weight of graphite, and 2 parts by weight of carbon black were dry-mixed at a stirring speed of 20 r / min for 30 min. Next, 5 parts by weight of polyacrylic acid was added and stirred at a stirring speed of 25 r / min for 30 min. Dispersion was carried out at a dispersion rotation speed of 40 r / min and a dispersion disk of 4000 r / min for 3 h, and water was added for adjustment to obtain a negative electrode slurry with a solid content of 35 wt%, and its viscosity was 4200 mPa·s -1 is.

[0048] By means of the double-sided coating technology, the progress speed of coating was controlled to 30 m / min, and the anode slurry was coated on the surface of the modified carbon fiber. After drying at 100 °C, roll pressing, and sheet punching, a silicon-based anode sheet was formed. The SEM diagram of the silicon-based anode sheet is shown in Figure 2.

[0049] Example 2 It is different from Example 1 in that a dopamine monomer buffer solution containing 0.2 parts by weight of dopamine monomer is used, and finally a silicon-based anode sheet was obtained.

[0050] Example 3 It is different from Example 1 in that a dopamine monomer buffer solution containing 5 parts by weight of dopamine monomer is used, and finally a silicon-based anode sheet was obtained.

[0051] Example 4 It is different from Example 1 in that a dopamine monomer buffer solution containing 0.1 parts by weight of dopamine monomer is used, and finally a silicon-based anode sheet was obtained.

[0052] Example 5 It is different from Example 1 in that a porous current collector (carbon fiber cloth) was added, the porosity of the obtained modified carbon fiber was 90%, and its pore size was 50-80 μm, and finally a silicon-based anode sheet was obtained.

[0053] Example 6 It is different from Example 1 in that the concentration of the dopamine monomer buffer solution was 3 g / L, the porosity of the obtained modified carbon fiber was 45%, and its pore size was 50-60 μm, and finally a silicon-based anode sheet was obtained.

[0054] Example 7 A nitric acid solution with a concentration of 50 wt% was added. It is different from Example 1 in that the porosity of the obtained modified carbon fiber was 50%, and its pore size was 50-70 μm, and finally a silicon-based anode sheet was obtained.

[0055] Example 8 A nitric acid solution with a concentration of 90 wt% was added. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 80%, and its pore diameter was 50 - 80 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0056] Example 9 A nitric acid solution with a concentration of 40 wt% was added. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 45%, and its pore diameter was 50 - 70 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0057] Example 10 The oxidation treatment time was 20 min. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 50%, and its pore diameter was 50 - 70 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0058] Example 11 The oxidation treatment time was 60 min. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 80%, and its pore diameter was 50 - 80 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0059] Example 12 The oxidation treatment time was 15 min. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 45%, and its pore diameter was 30 - 48 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0060] Example 13 The immersion time was 10 h. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 80%, and its pore diameter was 50 - 80 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0061] Example 14 The immersion time was 24 h. It was different from Example 1 in that the porosity of the modified carbon fiber obtained was 80%, and its pore diameter was 50 - 100 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0062] Example 15 This is different from Example 1 in that the immersion time was 5 h, the porosity of the obtained modified carbon fiber was 40%, and its pore size was 30 - 45 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0063] Example 16 This is different from Example 1 in that a double-sided coating technique was used, the coating progress speed was controlled at 50 m / min, the porosity of the obtained modified carbon fiber was 80%, and its pore size was 50 - 80 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0064] Example 17 This is different from Example 1 in that the solid content of the negative electrode slurry was 50 wt%, the porosity of the obtained modified carbon fiber was 80%, and its pore size was 50 - 80 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0065] Example 18 The viscosity of the negative electrode slurry was 7000 mPa·s -1 This is different from Example 1 in that the porosity of the obtained modified carbon fiber was 80%, and its pore size was 50 - 80 μm. Finally, a silicon-based negative electrode sheet was obtained.

[0066] Example 19 This is different from Example 1 in that the negative electrode slurry was applied to the surface of the modified carbon fiber, dried at 60°C, roll-pressed, and sheet-punched to form a silicon-based negative electrode sheet.

[0067] Example 20 This is different from Example 1 in that 50 parts by weight of silicon oxide SiO and 50 parts by weight of graphite were used. Finally, a silicon-based negative electrode sheet was obtained.

[0068] Example 21 This is different from Example 1 in that 20 parts by weight of silicon oxide SiO and 80 parts by weight of graphite were used. Finally, a silicon-based negative electrode sheet was obtained.

[0069] Example 22 This differed from Example 1 in that the silicon oxide SiO was 60 parts by weight and the graphite was 40 parts by weight, and finally a silicon-based negative electrode sheet was obtained.

[0070] Example 23 This differed from Example 1 in that the carbon fiber TGP-H-60 was 15 parts by weight, and finally a silicon-based negative electrode sheet was obtained.

[0071] Example 24 This differed from Example 1 in that the carbon fiber TGP-H-60 was 5 parts by weight, and finally a silicon-based negative electrode sheet was obtained.

[0072] Example 25 This differed from Example 1 in that the carbon fiber TGP-H-60 was 4 parts by weight, and finally a silicon-based negative electrode sheet was obtained.

[0073] Example 26 This differed from Example 1 in that the negative electrode slurry was applied as it was to the surface of carbon fiber that was not surface-modified, dried at 100 °C, roll-pressed, and sheet-punched, and then a silicon-based negative electrode sheet was formed.

[0074] Comparative Example 1 This differed from Example 1 in that the negative electrode slurry was applied as it was to the surface of the copper current collector, dried at 100 °C, roll-pressed, and sheet-punched, and then a copper-based negative electrode sheet was formed. Table 1 shows the porosity, pore diameter, and thickness values of the electrode sheets of the carbon fibers obtained in Examples 1 to 26.

[0075]

Table 1

[0076] The silicon-based negative electrode sheet and the NCM ternary positive electrode (standard WXO4Mg) according to each of the above Examples 1 to 26 were assembled to form a battery, and the copper-based negative electrode sheet and the NCM ternary positive electrode (standard WXO4Mg) according to Comparative Example 1 were assembled to form a battery. The cycle numbers were measured respectively when the cycle capacity retention rate of the battery was 80% at 25 °C, a voltage range of 2.5 to 4.25 V, and 1C, and the measurement results are shown in Table 2.

[0077]

Table 2

[0078] As is clear from the above description, according to the above Examples of the present invention, the following technical effects were achieved.

[0079] On the one hand, due to the network structure of the porous carbon material itself, the resistivity of the silicon-based negative electrode sheet is extremely reduced, the toughness of the silicon-based negative electrode sheet is increased, and further expansion of the silicon-based negative electrode sheet is effectively prevented. On the other hand, the surface of the silicon-carbon material particles is coated by the network structure of the porous carbon material itself, and a highly conductive, robust and permanent connection is established between the silicon particles.

[0080] Even when volume expansion and cracks begin to occur in the silicon particles, the porous carbon material can maintain a good connection between the silicon particles, thereby preventing the rupture of the silicon-carbon material, and at the same time bringing high capacity to the lithium-ion battery, and excellent cycle stability, initial efficiency and other electrical performances can also be achieved simultaneously.

[0081] In addition, the porous carbon material has the advantages of low density, low cost and corrosion resistance compared with the metal current collector. Therefore, by using the porous carbon material as the negative electrode current collector, while reducing the content of the conductive agent in the silicon-based negative electrode sheet, the mixing ratio of the silicon-carbon material in the whole silicon-based negative electrode sheet can be improved, and the energy density of the electric core can be further improved.

[0082] The above description is merely a preferred embodiment of the present invention and does not limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. All corrections, equivalent replacements, improvements, etc. made within the scope not departing from the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A silicon-based negative electrode sheet having a porous current collector and a silicon-containing material adhered in the pores of the porous current collector, wherein the porous current collector is a porous carbon material, a silicon-based negative electrode sheet.

2. The porosity of the porous current collector is 50% to 90%, preferably, the pore diameter of the porous current collector is 50 μm to 100 μm, and more preferably, the porous current collector is any one or more selected from carbon fibers, carbon fiber cloths, carbon nanotubes, and foamed carbon, The silicon-based negative electrode sheet according to Claim 1.

3. The silicon-based negative electrode sheet further includes a functional auxiliary agent for adhering the porous current collector and the silicon-containing material, the mass ratio of the porous current collector to the silicon-containing material is preferably 5 to 15:100, the mass of the functional auxiliary agent is preferably 0.2% to 5% of the silicon-containing material, the silicon-containing material is preferably any one or more selected from silicon oxide, silicon carbide, micrometer silicon, nanometer silicon, silicon oxide modified by pre-doping with lithium, and a mixture in which graphite and silicon oxide are mixed, more preferably, the silicon-containing material is a mixture in which graphite and silicon oxide are mixed, the mass ratio of the silicon oxide to the graphite in the mixture is preferably 1:1 to 4, and the functional auxiliary agent is preferably a dopamine monomer, The silicon-based negative electrode sheet according to Claim 1 or 2.

4. The thickness of the silicon-based negative electrode sheet is 6 μm to 200 μm, the silicon-based negative electrode sheet preferably further includes an adhesive and a conductive agent, the adhesive is preferably any one or more selected from styrene-butadiene rubber, sodium carboxymethyl cellulose, and polyvinyl alcohol, and the conductive agent is preferably any one or more selected from carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphene, The silicon-based negative electrode sheet according to any one of Claims 1 to 3.

5. A method for manufacturing the silicon-based negative electrode sheet according to any one of Claims 1 to 4, Step S1: a step of obtaining an active current collector by applying a negative electrode slurry containing a silicon-containing material to the surface of a porous current collector, Step S2: obtaining a silicon-based negative electrode sheet by drying, roll-pressing, and sheet punching the active current collector, and, manufacturing method.

6. Step S1 includes a surface modification treatment on a porous current collector, The process of the surface modification treatment is, Step S11: obtaining an oxidized current collector by oxidizing the porous current collector with an oxidant solution; Step S12: obtaining a washed current collector by washing the oxidized current collector; Step S13: obtaining a modified porous current collector by immersing the washed current collector in a functional auxiliary agent solution, preferably including, The oxidizing agent solution is a nitric acid solution with a concentration of 50% to 90 wt%, preferably, the time of the oxidation treatment is 20 min to 60 min, and preferably, the residual amount of NO ３ - in the current collector after washing is less than 50 ppm. the functional auxiliary agent solution is preferably a dopamine monomer solution, the concentration of the dopamine monomer solution is preferably 2 g / L to 3 g / L, and the solvent in the dopamine monomer solution is preferably a Tris-HCl buffer solution, the immersion time is preferably 10 h to 24 h, The manufacturing method according to claim 5.

7. In step S1, The coating is simultaneously performed on the opposing surfaces of the porous current collector. Preferably, the progress rate of the coating is 10 m / min to 50 m / min. Preferably, the solid content of the negative electrode slurry is 35% to 50 wt%. Preferably, the viscosity of the negative electrode slurry is 3000 mPa·S -1 to 7000 mPa·S -1 is The manufacturing method according to claim 5 or 6.

8. In step S2, the drying temperature is 60°C to 150°C, The manufacturing method according to claim 5 or 6.

9. A lithium-ion battery having a positive electrode sheet, an electrolyte, and a negative electrode sheet, wherein the negative electrode sheet is the silicon-based negative electrode sheet according to any one of claims 1 to 4, Lithium-ion battery.

10. Connecting the porous current collector of the silicon-based negative electrode sheet and the metal wire of the lithium-ion battery with a metal crimping sleeve, The lithium-ion battery according to claim 9.

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