A carbon-coated current collector, a preparation method thereof, and a secondary battery

Abstract

The present invention provides a carbon-coated current collector, a preparation method thereof, and a secondary battery. The carbon-coated current collector includes a conductive substrate and a carbon-coated layer; the carbon-coated layer includes a conductive agent and a fiber reinforcing material. The percentage of the mass of the fiber reinforcing material in the mass of the conductive agent is 5% to 30%. The fiber reinforcing material includes reinforcing fibers and a resin material. The reinforcing fibers include glass fibers and carbon fibers; the mass of carbon fibers: the mass of glass fibers ≥ 4; the percentage of the mass of glass fibers in the mass of the conductive agent is 0.2% to 5%. The carbon-coated current collector provided by this solution has good high-temperature resistance and moisture resistance, so that the carbon-coated current collector can well adapt to different external environments and maintain good structural stability.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and specifically, relates to a carbon-coated current collector, a preparation method thereof, and a secondary battery. Background Art

[0002] Lithium-ion batteries (LIBs) have been widely accepted in many fields such as consumer electronics, transportation, power tools, and energy storage. The current collector is an indispensable component of lithium-ion batteries, playing an important role in carrying active materials (load-bearing property) and collecting microcurrents (conductivity). To adapt to the rapid development of lithium-ion batteries, current collector technology is constantly innovating. The composite current collector with a "metal-polymer substrate-metal" sandwich structure has subverted the traditional foil current collector. Compared with the traditional foil current collector, the composite current collector has a series of advantages such as lower cost and higher safety. In addition, in order to improve the performance of lithium-ion batteries in the lithium battery industry, a strategy of preparing a carbon-coated current collector by adding a carbon-coated layer on the surface of the current collector is adopted to improve other electrochemical properties such as the rate performance of lithium-ion batteries.

[0003] During the process of storing and applying the current collector in lithium-ion production, processes such as slitting and winding are generally involved. The stress exerted on the current collector by the machinery and equipment used in the above processes during the above processes may cause irreversible deformation of the current collector, resulting in deterioration of the performance of the current collector. Severe deformation may even cause the current collector to fail. In particular, compared with the traditional foil current collector, the mechanical strength of the composite current collector based on a polymer substrate is worse, making the adverse effects of external stress on the composite current collector more obvious. In summary, it is necessary to improve the resistance of the current collector to external adverse stress through material development and research. Summary of the Invention

[0004] In order to balance the conductivity of the current collector and achieve the improvement of the structural stability and moisture and heat resistance of the current collector, the present invention provides a carbon-coated current collector, a preparation method thereof, and a secondary battery.

[0005] According to a first aspect of the present invention, a carbon-coated current collector is provided. The carbon-coated current collector includes a conductive substrate and a carbon-coated layer; the carbon-coated layer includes a conductive agent and a fiber reinforcement material. The percentage of the mass of the fiber reinforcement material in the mass of the conductive agent is 5% to 30%. The fiber reinforcement material includes reinforcing fibers and a resin material. The reinforcing fibers include glass fibers and carbon fibers; the mass ratio of carbon fibers to glass fibers is ≥4; the percentage of the mass of glass fibers in the mass of the conductive agent is 0.2% to 5%. The reinforcing fibers adopted in this solution all have the characteristics of high strength, high stiffness, low density, and good corrosion resistance. Among them, glass fibers have obvious advantages in mechanical properties, while carbon fibers have excellent electrical conductivity. Using carbon fibers and glass fibers in combination can significantly improve the toughness of the carbon-coated layer while maintaining good electrical conductivity of the carbon-coated layer. By strengthening the structural stability of the current collector through the carbon-coated layer with high toughness, adverse mechanical deformations of the current collector caused by external stress can be reduced. On the other hand, glass fibers are sensitive to humidity and are prone to corrosion and degradation in a high-humidity environment. By using carbon fibers and glass fibers in combination, the sensitivity of glass fibers to humidity can be effectively reduced, so that the carbon-coated current collector provided by this solution has good moisture resistance. In addition, this solution uses a resin material and a reinforcing material to jointly form a fiber reinforcement material. The resin material provides protection for the reinforcing fibers, and can significantly improve the high-temperature resistance characteristics of the carbon-coated current collector, reducing adverse deformations of the carbon-coated layer and the carbon-coated current collector caused by thermodynamical residual stress. In summary, by constructing a fiber reinforcement material with carbon fibers, glass fibers and a resin material and introducing the above fiber reinforcement material into the carbon-coated layer of the carbon-coated current collector, this solution can keep the carbon-coated layer with good electrical conductivity, significantly improve the toughness of the carbon-coated layer, and further improve the resistance of the carbon-coated current collector to external stress. And this carbon-coated current collector has good high-temperature resistance and moisture resistance, so that this carbon-coated current collector can well adapt to different external environments and maintain good structural stability.

[0006] Preferably, the conductive agent includes at least one of graphite and carbon black.

[0007] Preferably, the conductive agent includes carbon black and graphite. Calculated by mass percentage, in the conductive agent, the proportion of carbon black is 70% to 90%, and the proportion of graphite is 10% to 30%.

[0008] Preferably, the thickness of the conductive substrate is 8 μm to 12 μm.

[0009] Preferably, the conductive substrate is composed of a metal layer, a polymer substrate, and a metal layer arranged in sequence. When the structure of the conductive substrate meets the above characteristics, the current collector belongs to a composite current collector. In the composite current collector, the thickness of the polymer substrate can generally reach 4 μm to 8 μm. After adding metal layers on both sides of the polymer substrate, the thickness of the conductive substrate can reach 8 μm to 12 μm. However, the composite current collector based on the polymer substrate shows deficiencies in toughness and conductivity compared with the traditional foil current collector. In this solution, by applying a carbon-coated layer with high toughness and high conductivity to the composite current collector, the structural strength and conductivity of the composite current collector can be effectively improved, which is beneficial to giving full play to the advantages of the composite current collector.

[0010] Preferably, the thickness of any carbon-coated layer reaches 2 μm to 6 μm.

[0011] Preferably, in the carbon-coated current collector, the total thickness of the carbon-coated layer reaches more than 50% of the thickness of the conductive substrate. This can enable the mechanical superiority of the carbon-coated layer to be better reflected in the conductive substrate.

[0012] Preferably, the preparation of the above fiber-reinforced material includes the following steps: S1. Mix the reinforcing fiber and the resin material in proportion to obtain a premix; S2. Perform cryogenic treatment on the premix, and the treatment temperature of the cryogenic treatment is -210°C to -190°C; S3. Extrude the premix that has undergone cryogenic treatment; S4. Heat the premix to first transform it into a flowable slurry state and then cure the premix into a molded form. In the above preparation process, by performing cryogenic treatment on the premix, the following effects can be achieved: ① The adhesiveness of the resin material can be reduced, the wettability performance of the carbon fiber can be improved, and the bonding strength between the reinforcing fiber and the resin material can be increased; ② It is beneficial to improve the mechanical stability of the reinforcing fiber, including improving strength and stiffness, etc., avoiding damage during the processing process, and also reducing the deformation and warping of the carbon-coated current collector; ③ The fluidity of the resin material is reduced, so that the controllability of the processing of the carbon-coated layer is improved, the quality stability of the carbon-coated layer is improved, and the yield of high-quality products is increased. If the fluidity of the resin material is too high, during the preparation of the carbon-coated current collector, the processing controllability of the fiber-reinforced material containing the resin material is poor, and it is easy to cause structural defects in the carbon-coated layer.

[0013] Preferably, in S2, the cryogenic treatment conditions involved can be realized by using liquid nitrogen as the cryogenic medium. Specifically, the premix is put into liquid nitrogen for 2 to 5 minutes and then taken out.

[0014] Preferably, the process of preparing the fiber-reinforced material further includes pre-treating the reinforcing fibers before step S1. The pre-treating includes heating the reinforcing fibers at a temperature of 400° C. to 900° C. The pre-treating operation can reduce the toughness of the reinforcing fibers to a certain extent, thereby promoting uniform mixing of the reinforcing fibers and the resin material.

[0015] Preferably, when the reinforcing fiber is glass fiber, the heating temperature in the pretreatment is 400°C to 600°C; when the reinforcing fiber is carbon fiber, the heating temperature in the pretreatment is 700°C to 900°C.

[0016] Preferably, the process of preparing the fiber-reinforced material further includes, before S1, subjecting the resin material to viscosity adjustment, including the following operations: immersing the resin material in an alcohol solvent, allowing the resin material to stand, and then removing the resin material. The viscosity adjustment step reduces the viscosity of the resin material, making it easier to mix with the reinforcing fibers and form the resin.

[0017] Preferably, the fiber-reinforced material includes glass fiber-reinforced material and carbon fiber-reinforced material. The glass fiber-reinforced material contains glass fiber as the reinforcing fiber, while the carbon fiber-reinforced material contains carbon fiber as the reinforcing fiber. In the glass fiber-reinforced material, the mass ratio of glass fiber to resin material is 1:4-6; in the carbon fiber-reinforced material, the mass ratio of carbon fiber to resin material is 1:1-3. By combining glass fiber and carbon fiber with resin material to prepare fiber-resin composite reinforcements, the respective ratios of glass fiber and carbon fiber to resin material are determined based on their respective properties. This can further improve the structural strength and heat resistance of the carbon-coated current collector (relieving material deformation caused by thermodynamic residual stress).

[0018] Preferably, the mass ratio of the glass fiber reinforcement material to the carbon fiber reinforcement material is ≥1 / 3.

[0019] Preferably, the resin material includes at least one of epoxy resin material, polyester resin material, and acrylic resin material.

[0020] Preferably, the carbon-coated current collector satisfies at least one of the following a, b, and c:

[0021] a. The glass fiber includes a fiber with a length of 10 mm or more, and the resin material contained in the glass fiber reinforced material includes at least one of an epoxy resin material and a polyester resin material;

[0022] b. Carbon fiber with a length of 10 mm or more, the resin material contained in the carbon fiber reinforced material includes at least one of epoxy resin material and polyester resin material;

[0023] c. The percentage of the mass of carbon fiber in the mass of the conductive agent is 0.1% to 0.5%, and the resin material contained in the carbon fiber reinforced material includes at least one of epoxy resin material and polyester resin material.

[0024] According to the second aspect of the present invention, there is provided a method for preparing the above-mentioned carbon-coated current collector, including the following operations: preparing a carbon-coated slurry, and coating the carbon-coated slurry on the surface of the conductive substrate to form a carbon-coated layer on the surface of the conductive substrate; during the process of preparing the carbon-coated slurry, the feeding sequence of the conductive agent and the fiber reinforcing material is as follows: first, part of the conductive agent is added to the glue containing the binder, then the glass fiber reinforcing material is added, and then the remaining conductive agent is added. After the addition of the conductive agent is completed, the carbon fiber reinforcing material is added. During the above process of preparing the carbon-coated slurry, the conductive agent is added in two portions, which is beneficial to accurately control the viscosity of the slurry and prevent the slurry from thickening sharply. The glass fiber and the carbon fiber are added to the slurry in sequence before and after the addition of the conductive agent, respectively. Thus, the two different reinforcing fibers can be evenly interspersed in the conductive agent, improving the dispersibility of the carbon-coated slurry. In summary, based on the method for preparing the carbon-coated slurry adopted in this solution, the coating performance of the carbon-coated slurry can be improved, which is beneficial to the better functioning of the carbon-coated layer. The binder adopted above may include at least one of acrylate, polyacrylic acid, modified polyacrylic acid, and waterborne polyurethane.

[0025] Preferably, the binder is modified waterborne polyacrylic acid.

[0026] Preferably, the solid content of the glue is 15% to 30%. The solid content of the glue can be 15%, 16%, 17%, 18%, 20%, 22%, 25%, 30%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0027] Preferably, the viscosity of the glue is 200 mPa·s to 1500 mPa·s. The viscosity of the glue can be 200 mPa·s, 300 mPa·s, 400 mPa·s, 500 mPa·s, 550 mPa·s, 600 mPa·s, 650 mPa·s, 700 mPa·s, 750 mPa·s, 800 mPa·s, 850 mPa·s, 900 mPa·s, 950 mPa·s, 1000 mPa·s, 1050 mPa·s, 1100 mPa·s, 1200 mPa·s, 1300 mPa·s, 1400 mPa·s, 1500 mPa·s, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0028] Preferably, in the above method for preparing the carbon-coated current collector, the process of preparing the carbon-coated slurry includes the following operations:

[0029] Step 1, preparing glue containing a binder;

[0030] Step 2: Add 30% to 60% of conductive agent to the glue and disperse it fully;

[0031] Step 3: Add glass fiber reinforcement to the slurry obtained in step 2 and fully disperse it;

[0032] Step 4: adding the remaining conductive agent to the slurry obtained in step 3 and fully dispersing it;

[0033] Step 5: Add carbon fiber reinforcement material to the slurry obtained in step 4 and fully disperse it;

[0034] Step six, adjusting the viscosity and pH value of the slurry obtained in step five.

[0035] Optionally, the mixing process for preparing the carbon coating slurry can be carried out in a double star stirring tank.

[0036] Preferably, in the above step 2, the dispersion speed of the dispersed slurry is 2000 rpm / min to 2600 rpm / min.

[0037] Preferably, in the above step 3, the dispersion speed of the dispersed slurry is 1000 rpm / min to 1500 rpm / min.

[0038] Preferably, in the above step 4, the dispersion speed of the dispersed slurry is 2000 rpm / min to 2600 rpm / min.

[0039] Preferably, in the above step 5, the dispersion speed of the dispersed slurry is 1000 rpm / min to 1500 rpm / min.

[0040] Preferably, in the above step 6, the pH of the slurry is adjusted to 5-7.

[0041] Preferably, the process of preparing the carbon coating slurry further comprises step seven, in which a wetting agent is added to the slurry obtained in step six. The wetting agent may include at least one of polyether siloxane, modified polyether siloxane, and an alcohol reagent.

[0042] Preferably, the wetting agent comprises a modified polyether siloxane.

[0043] According to a third aspect of the present invention, there is provided a secondary battery comprising the carbon-coated current collector as described above. DETAILED DESCRIPTION

[0044] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0045] Example 1

[0046] In this embodiment, a carbon-coated current collector is prepared, and the related operations involved are described in detail below.

[0047] 1. Preparation of carbon-coated slurry

[0048] (1) Preparation of fiber-reinforced material

[0049] The main materials for preparing the fiber-reinforced material in this embodiment are as follows: The resin material used is epoxy vinyl ester resin, purchased from Ashland Group, with the product model DM411-350; the glass fiber used is purchased from Owens Corning, with the model Fiberglas™ 600. The diameter of the glass fiber is concentrated between 0.01 mm and 0.05 mm, and the length of the glass fiber is concentrated between 1 mm and 10 mm, but there are some that can reach 20 mm to 30 mm or longer; the carbon fiber used is purchased from Merck Chemical, and the official website product information is graphitized, platelets (conical), >98% carbon basis. The diameter of the carbon fiber is concentrated between 0.005 mm and 0.01 mm, and the length of the carbon fiber is concentrated between 1 mm and 10 mm, but there are some that can reach 20 mm to 30 mm or longer.

[0050] 1) Glass fiber-reinforced material

[0051] The preparation of the glass fiber-reinforced material is carried out according to the following steps:

[0052] S0. (Pretreatment step) Prepare materials according to the mass ratio of resin material: glass fiber = 5:1; place the resin material in methanol with a concentration of 20% and let it stand for 60 min and then take it out; place the glass fiber in a mortar, manually grind it for 30 min, and then place it in a tubular furnace and heat it at 500 °C for 1 hour.

[0053] S1. Place the glass fiber and resin material pretreated in S0 in a large-capacity centrifuge tube, centrifuge and stir at 3500 r / min for 6 hours to obtain a premix. Place the centrifuge tube containing the premix in a low-temperature box for 30 min to cool down until the temperature of the centrifuge tube drops to room temperature.

[0054] S2. Perform low-temperature treatment on the premix. The specific operation method is to quickly place the centrifuge tube containing the premix in liquid nitrogen for 3 minutes and then take it out. After the low-temperature treatment, the premix becomes brittle. Take out the brittle premix in the centrifuge tube from liquid nitrogen, wrap it with dust-free paper, place it under an extruder, and extrude it 3 times with a pressure of 30 MPa.

[0055] S3. After extrusion, place the formed premix in a curing device. At a temperature of 50 °C and a pressure of 10 MPa, the resin material hardens, and the glass fiber combines with the resin material to complete the production of the glass fiber reinforced material.

[0056] 2) Carbon fiber reinforced material

[0057] The preparation of the carbon fiber reinforced material is carried out according to the following steps:

[0058] S0. (Pretreatment step) Prepare materials according to the mass ratio of resin material: carbon fiber = 2:1; place the resin material in methanol with a concentration of 20% and let it stand for 60 minutes and then take it out; place the carbon fiber in a mortar, manually grind it for 30 minutes, and then place it in a tube furnace and heat it at 800 °C for 1 hour.

[0059] S1. Place the carbon fiber and resin material pretreated in S0 in a large-capacity centrifuge tube, centrifuge and stir at 3500 r / min for 6 hours to obtain a premix. Place the centrifuge tube containing the premix in a low-temperature box for 30 minutes to cool down until the temperature of the centrifuge tube drops to room temperature.

[0060] S2. Perform low-temperature treatment on the premix. The specific operation method is to quickly place the centrifuge tube containing the premix in liquid nitrogen for 3 minutes and then take it out. After the low-temperature treatment, the premix becomes brittle. Take out the brittle premix in the centrifuge tube from liquid nitrogen, wrap it with dust-free paper, place it under an extruder, and extrude it 2 times with a pressure of 20 MPa.

[0061] S3. After extrusion, place the formed premix in a curing device. At a temperature of 50 °C and a pressure of 3 MPa, the resin material hardens, and the carbon fiber combines with the resin material to complete the production of the carbon fiber reinforced material.

[0062] (2) Prepare the carbon-coated slurry

[0063] Prepare materials: Weigh the above materials according to the mass ratio of glass fiber reinforced material: carbon fiber reinforced material = 1:4. Calculate the mass of the conductive agent according to the total mass of the glass fiber reinforced material and the carbon fiber reinforced material. The total mass of the glass fiber reinforced material and the carbon fiber reinforced material accounts for 20% of the mass of the conductive agent. Among them, the conductive agent includes carbon black and graphite. Calculated according to the mass ratio, carbon black: graphite = 85:15. Use modified water-based polyacrylic acid as the binder. Use modified polyether siloxane as the wetting agent.

[0064] The carbon coating slurry is prepared according to the following steps:

[0065] Step 1: Mix deionized water and a binder to prepare glue, and adjust the amount of deionized water so that the viscosity of the glue is 200 mPa·s;

[0066] Step 2: Transfer the glue into a 200L Double Star mixing tank, add 50% of the total amount of carbon black and 50% of the total amount of graphite to the glue, and disperse the resulting slurry at a high speed of 2400 rpm / min for 30 minutes;

[0067] Step 3: Add glass fiber reinforcement to the slurry obtained in step 2, and disperse the slurry at a high speed of 1200 rpm / min for 30 minutes;

[0068] Step 4: Add the remaining carbon black and graphite to the slurry obtained in step 3, and disperse the resulting slurry at a high speed of 2400 rpm / min for 60 minutes;

[0069] Step 5: Add carbon fiber reinforcement material to the slurry obtained in step 4, and disperse the slurry at a high speed of 1200 rpm / min for 60 minutes;

[0070] Step 6: Deionized water was added to the slurry obtained in step 5 to adjust the viscosity of the slurry to 100 mPa·s. The slurry was dispersed at a high speed of 2400 rpm / min for 30 minutes. Then, a pH value was adjusted to 6 by adding a pH meter to the slurry.

[0071] Step 7: Add a wetting agent to the slurry of step 6 at a rate of 10% of the feed amount, and disperse the resulting slurry at a low speed of 10 rpm / min for 40 minutes, and then discharge the slurry;

[0072] Step eight, the slurry thus prepared is transferred to a homogenizer, homogenized twice at a pressure of 300 bar, and discharged to prepare a carbon-coated slurry.

[0073] 2. Preparation of Carbon-Coated Current Collectors

[0074] The conductive substrate used as the carbon-coated current collector in this embodiment is composed of a polymer substrate and metal aluminum layers respectively arranged on two surfaces of the polymer substrate, wherein the polymer substrate is made of PET with a thickness of 6 μm, and the thickness of the single-layer metal aluminum layer is 1 μm.

[0075] The carbon coating slurry prepared in this example was evenly coated on two opposite surfaces of the polymer substrate and dried to form a carbon coating layer with a thickness of 5 μm on each of the two opposite surfaces of the polymer substrate.

[0076] Example 2

[0077] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The difference from Example 1 is that the carbon-coated slurry is prepared using a mass ratio of 1:2 for glass fiber reinforcement and 1:2 for carbon fiber reinforcement. Other than these differences, the materials used and other specific procedures for preparing the carbon-coated current collector in this example remain strictly consistent with those in Example 1.

[0078] Example 3

[0079] This example prepared a carbon-coated current collector using the same method as in Example 1. The difference from Example 1 is that the carbon-coated slurry was prepared using a mass ratio of 1:3 for glass fiber reinforcement and 1:3 for carbon fiber reinforcement. Other than these differences, the materials used and other specific procedures for preparing the carbon-coated current collector in this example remained strictly consistent with those in Example 1.

[0080] Example 4

[0081] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The difference from Example 1 is that during the carbon coating slurry application step, the coating amount is adjusted so that a 1 μm thick carbon coating layer is ultimately formed on each of the two opposing surfaces of the polymer substrate. Apart from these differences, the materials used and other specific procedures for preparing the carbon-coated current collector in this example remain strictly consistent with those in Example 1.

[0082] Example 5

[0083] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The differences from Example 1 are that during the preparation of the glass fiber-reinforced material, the low-temperature treatment of the glass fibers (Step 2) is omitted; during the preparation of the carbon fiber-reinforced material, the low-temperature treatment of the carbon fibers (Step 2) is omitted. Apart from these differences, the materials used and other specific procedures for preparing the carbon-coated current collector in this example are strictly consistent with those in Example 1.

[0084] Example 6

[0085] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The differences from Example 1 are that the heating pretreatment of the glass fibers in S0 is omitted during the preparation of the glass fiber-reinforced material, and the heating pretreatment of the carbon fibers in S0 is omitted during the preparation of the carbon fiber-reinforced material. Aside from these differences, the materials used and other specific procedures for preparing the carbon-coated current collector in this example remain strictly consistent with those in Example 1.

[0086] Example 7

[0087] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The difference from Example 1 is that during the preparation of the glass fiber reinforcement, the heating temperature for the glass fiber pretreatment in S0 is adjusted from 500°C to 800°C. Apart from these differences, the materials used and other specific operations in preparing the carbon-coated current collector in this example are strictly consistent with those in Example 1.

[0088] Example 8

[0089] This example prepared a carbon-coated current collector using the same method as in Example 1. The difference from Example 1 is that during the preparation of the carbon fiber-reinforced material, the heating temperature for the carbon fiber pretreatment in S0 was adjusted from 800°C to 500°C. Apart from these differences, the materials used and other specific operations during the preparation of the carbon-coated current collector in this example were strictly consistent with those in Example 1.

[0090] Example 9

[0091] This example prepares a carbon-coated current collector by referring to the method for preparing a carbon-coated current collector in Example 1. The differences from Example 1 are as follows: in the preparation of the glass fiber reinforced material, the mass of the resin material: the mass of the glass fiber is 2:1; in the preparation of the carbon fiber reinforced material, the mass of the resin material: the mass of the carbon fiber is 2:1; in the preparation of the carbon fiber reinforced material, the mass of the resin material: the mass of the carbon fiber is 2:1; in the preparation of the carbon-coated slurry, the composition of the conductive agent used is consistent with that in Example 1, and the amounts of the carbon fiber reinforced material and the glass reinforced material are calculated according to the mass ratio of the conductive agent to the mass of the carbon fiber and the mass of the glass fiber in Example 1, so that the carbon-coated slurry prepared in this example and the carbon-coated slurry prepared in Example 1 have the same mass ratio of glass fiber to carbon fiber; in the application of the carbon-coated slurry, the coating thickness is controlled so that the total mass of the reinforcing material corresponding to the carbon coating layer per unit area of the polymer substrate surface is equal in the carbon-coated current collector prepared in this example and the carbon-coated current collector prepared in Example 1. Aside from the above differences, the materials used in the preparation of the carbon-coated current collector in this example and other specific operations are strictly consistent with those in Example 1. Based on the above differences, when the polymer substrates used are of the same size, the carbon-coated current collector prepared in this embodiment is compared with the carbon-coated current collector prepared in Example 1. The component composition and mass dosage of the conductive agent in the carbon coating layer, the mass dosage of the glass fiber, and the mass dosage of the carbon fiber remain equal. The only difference in the amount of materials used is the mass dosage of the resin material.

[0092] Example 10

[0093] This example refers to the solution for preparing a carbon-coated current collector in Example 1 to prepare a carbon-coated current collector. The differences from Example 1 are as follows: During the preparation of the glass fiber reinforced material, the mass ratio of the resin material to the glass fiber is 1:1; during the preparation of the carbon fiber reinforced material, the mass ratio of the resin material to the carbon fiber is 2:1; during the preparation of the carbon-coated slurry, the component composition of the conductive agent used is the same as that in Example 1. The amounts of the carbon fiber reinforced material and the glass reinforced material are calculated respectively according to the mass ratio of the conductive agent in Example 1 to the mass of the carbon fiber and the glass fiber, so that the carbon-coated slurry prepared in this example has the same mass ratio of glass fiber to carbon fiber as the carbon-coated slurry prepared in Example 1; during the coating of the carbon-coated slurry, by controlling the coating thickness, the total mass of the reinforcing material corresponding to the carbon-coated layer covered per unit area on the surface of the polymer substrate of the carbon-coated current collector prepared in this example is equal to that of the carbon-coated current collector prepared in Example 1. Except for the above differences, the materials and other specific operations used in this example during the preparation of the carbon-coated current collector are strictly the same as those in Example 1. Based on the above differences, when the sizes of the polymer substrates used are the same, compared with the carbon-coated current collector prepared in Example 1, the component composition and mass dosage of the conductive agent, the mass dosage of the glass fiber, and the mass dosage of the carbon fiber in the carbon-coated layers of the two are equal. In terms of the dosage of materials, the only difference lies in the mass dosage of the resin material.

[0094] Example 11

[0095] This example prepares a carbon-coated current collector by referring to the method for preparing a carbon-coated current collector in Example 1. The differences from Example 1 are as follows: in the process of preparing the glass fiber reinforced material, the mass of the resin material: the mass of the glass fiber is 2:1; in the process of preparing the carbon fiber reinforced material, the mass of the resin material: the mass of the carbon fiber is 1:1; in the process of preparing the carbon-coated current collector, the component composition of the conductive agent used is consistent with that in Example 1, and the amount of the carbon fiber reinforced material and the glass reinforced material is calculated according to the mass ratio of the conductive agent to the mass of the carbon fiber and the mass of the glass fiber in Example 1, so that the carbon-coated current collector prepared in this example and the carbon-coated current collector prepared in Example 1 have the same mass ratio of glass fiber to carbon fiber; in the process of applying the carbon-coated current collector, the coating thickness is controlled so that the total mass of the reinforcing material corresponding to the carbon coating layer per unit area of the polymer substrate surface is equal to that of the carbon-coated current collector prepared in Example 1. Aside from the above differences, the materials used in this example and other specific operations in preparing the carbon-coated current collector are strictly consistent with those in Example 1. Based on the above differences, when the polymer substrates used are of the same size, the carbon-coated current collector prepared in this embodiment is compared with the carbon-coated current collector prepared in Example 1. The component composition and mass dosage of the conductive agent in the carbon coating layer, the mass dosage of the glass fiber, and the mass dosage of the carbon fiber remain equal. The only difference in the amount of materials used is the mass dosage of the resin material.

[0096] Example 12

[0097] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The only difference from Example 1 is that a polyester resin (manufactured by Xiamen Aikema Chemical Co., Ltd., model number ESC-2203) of equal quality is used in place of epoxy vinyl ester resin in the preparation of the fiber-reinforced material. Apart from these differences, the materials used and other specific procedures for preparing the carbon-coated current collector in this example strictly adhere to those in Example 1.

[0098] Embodiment 13

[0099] This example follows the same method used in Example 1 to prepare a carbon-coated current collector. The difference from Example 1 is that an acrylic resin (manufactured by Shandong Keyao Chemical Co., Ltd., model DS-501) of equal quality is used instead of epoxy vinyl ester resin as the resin material in the preparation of the fiber-reinforced material. Apart from these differences, the materials used and other specific procedures in preparing the carbon-coated current collector in this example strictly follow those in Example 1.

[0100] Embodiment 14

[0101] This example refers to the solution for preparing the carbon-coated current collector in Example 1 to prepare the carbon-coated current collector. The difference from Example 1 is that the preparation of the carbon-coated slurry in this example is carried out according to the following steps:

[0102] Step 1 is the same as Step 1 in preparing the carbon-coated slurry in Example 1;

[0103] Step 2 is the same as Step 2 in preparing the carbon-coated slurry in Example 1;

[0104] Step 3: Add glass fiber reinforcing material and carbon fiber reinforcing material to the slurry obtained in Step 2, and disperse the resulting slurry at a high speed for 30 minutes at a dispersion speed of 1200 rpm / min;

[0105] Step 4 is the same as Step 4 in preparing the carbon-coated slurry in Example 1;

[0106] Step 5: Add deionized water to the slurry obtained in Step 4. Other operations in this step are the same as those in Step 6 of preparing the carbon-coated slurry in Example 1;

[0107] Step 6: Add a wetting agent to the slurry obtained in Step 5 according to a feeding amount of 10%. Other operations in this step are the same as those in Step 7 of preparing the carbon-coated slurry in Example 1;

[0108] Step 7 is the same as Step 8 in preparing the carbon-coated slurry in Example 1.

[0109] Except for the above differences, the materials and other specific operations used in the process of preparing the carbon-coated current collector in this example are strictly the same as those in Example 1.

[0110] Example 15

[0111] This example refers to the solution for preparing the carbon-coated current collector in Example 1 to prepare the carbon-coated current collector. The difference from Example 1 is that in the process of preparing the carbon-coated slurry in this example, the feeding order of the glass fiber reinforcing material and the carbon fiber reinforcing material is swapped. Except for the above differences, the materials and other specific operations used in the process of preparing the carbon-coated current collector in this example are strictly the same as those in Example 1.

[0112] Comparative Example 1

[0113] This comparative example prepared a carbon-coated current collector with reference to the solution for preparing a carbon-coated current collector in Example 1. The difference from Example 1 is that the formulation for preparing the carbon-coated slurry does not contain glass fiber reinforcing material and carbon fiber reinforcing material, and the conductive agent is used to replace the glass fiber reinforcing material and carbon fiber reinforcing material in the formulation for preparing the carbon-coated slurry in Example 1 in equal mass, thereby obtaining the formulation for preparing the carbon-coated slurry in this comparative example. Among them, the component composition of the conductive agent used in this comparative example is consistent with that of the conductive agent used in Example 1; correspondingly, in the process of preparing the carbon-coated slurry in this comparative example, based on the process of preparing the carbon-coated slurry in Example 1, the feeding of the glass fiber reinforcing material is replaced by the conductive agent in equal mass, and the feeding of the carbon fiber reinforcing material is replaced by the conductive agent in equal mass, that is, in the finally prepared carbon-coated slurry, neither the glass fiber reinforcing material nor the carbon fiber reinforcing material is contained. Except for the above differences, the materials and other specific operations used in this comparative example in the process of preparing the carbon-coated current collector are strictly consistent with those in Example 1.

[0114] Comparative Example 2

[0115] This comparative example prepared a carbon-coated current collector with reference to the solution for preparing a carbon-coated current collector in Example 1. The difference from Example 1 is that the formulation for preparing the carbon-coated slurry does not contain glass fiber reinforcing material, and the carbon fiber reinforcing material is used to replace the glass fiber reinforcing material in the formulation for preparing the carbon-coated slurry in Example 1. The amount of the carbon fiber reinforcing material used to replace the glass fiber reinforcing material satisfies that the mass of the carbon fiber contained in this part of the carbon fiber reinforcing material is equal to the mass of the glass fiber contained in the replaced glass fiber reinforcing material, thereby obtaining the formulation for preparing the carbon-coated slurry in this comparative example. Among them, the carbon fiber reinforcing material used in this comparative example is consistent with the carbon fiber reinforcing material used in Example 1; correspondingly, in the process of preparing the carbon-coated slurry in this comparative example, based on the process of preparing the carbon-coated slurry in Example 1, the feeding of the glass fiber reinforcing material is replaced by the carbon fiber reinforcing material, that is, in the finally prepared carbon-coated slurry, the glass fiber reinforcing material is not contained, but the carbon fiber reinforcing material is contained. Except for the above differences, the materials and other specific operations used in this comparative example in the process of preparing the carbon-coated current collector are strictly consistent with those in Example 1.

[0116] Comparative Example 3

[0117] This comparative example prepared a carbon-coated current collector with reference to the solution for preparing the carbon-coated current collector in Example 1. The difference from Example 1 is as follows: in the formula for preparing the carbon-coated slurry, there is no carbon fiber reinforcing material, and the carbon fiber reinforcing material in the formula for preparing the carbon-coated slurry in Example 1 is replaced with a glass fiber reinforcing material. The dosage of the glass fiber reinforcing material used to replace the carbon fiber reinforcing material is such that the mass of the glass fibers contained in this part of the glass fiber reinforcing material is equal to the mass of the carbon fibers contained in the replaced carbon fiber reinforcing material. Thus, the formula for preparing the carbon-coated slurry in this comparative example is obtained. Among them, the glass fiber reinforcing material used in this comparative example is the same as that used in Example 1; correspondingly, in the process of preparing the carbon-coated slurry in this comparative example, based on the process of preparing the carbon-coated slurry in Example 1, the feeding of the carbon fiber reinforcing material is replaced with the glass fiber reinforcing material, that is, in the finally prepared carbon-coated slurry, there is no carbon fiber reinforcing material, but there is a glass fiber reinforcing material. Except for the above differences, the materials and other specific operations used in this comparative example in the process of preparing the carbon-coated current collector are strictly the same as those in Example 1.

[0118] Comparative Example 4

[0119] This comparative example prepared a carbon-coated current collector with reference to the solution for preparing the carbon-coated current collector in Example 1. The difference from Example 1 is as follows: this comparative example prepared the carbon-coated slurry by preparing materials according to the mass ratio of glass fiber reinforcing material: carbon fiber reinforcing material = 1:1. Except for the above differences, the materials and other specific operations used in this example in the process of preparing the carbon-coated current collector are strictly the same as those in Example 1.

[0120] Comparative Example 5

[0121] This comparative example prepared a carbon-coated current collector with reference to the solution for preparing the carbon-coated current collector in Example 1. The difference from Example 1 is as follows: this comparative example directly used the glass fibers and carbon fibers obtained after pretreatment and low-temperature treatment in Example 1 (corresponding to S0 - S2 in the preparation of the glass fiber reinforcing material and S0 - S2 in the preparation of the carbon fiber reinforcing material in Example 1) to replace the glass fiber reinforcing material and carbon fiber reinforcing material in Example 1 to participate in the preparation of the carbon-coated slurry, and determined the dosages of the glass fibers and carbon fibers in this comparative example according to the standard that the dosages of the glass fibers and carbon fibers are the same as those in Example 1. Except for the above differences, the materials and other specific operations used in this comparative example in the process of preparing the carbon-coated current collector are strictly the same as those in Example 1.

[0122] Test Example

[0123] 1. Test Object

[0124] The carbon-coated current collectors prepared in Examples 1 to 15 and Comparative Examples 1 to 5 were used as the test objects.

[0125] 2. Test Items and Test Methods

[0126] (1)Sheet Resistance Test

[0127] The sheet resistance of the test object was directly measured using a four-probe resistivity meter.

[0128] (2)Elongation Rate Test

[0129] The test object was cut into samples with dimensions of 10 cm × 4 cm. The positive electrode active slurry with lithium iron phosphate as the positive electrode active material was coated on the surface of the samples, and the single-sided coating surface density was 200 g / m 2 . After drying, the test samples were obtained. Then, the test samples were roll-pressed at a compaction density of 2.5 g, and the length changes of the test samples before and after roll-pressing were measured.

[0130] (3)Humidity Sensitivity Test

[0131] The test object was cut into samples with dimensions of 10 cm × 10 cm. The moisture content of the test samples was measured and recorded as X1. Then, the samples were placed in a room with a temperature of 25 °C and a humidity of 50 RH% for 30 days. After that, the moisture content of the test samples was measured and recorded as X2. The formula for calculating the humidity sensitivity rate is: Humidity sensitivity rate = (X2 - X1) × 100% / X1.

[0132] (4)Thermodynamic Deformation Test

[0133] The test object was cut into samples with dimensions of 10 cm × 10 cm. The samples were placed on A4 paper, and the side lengths of the samples in the transverse and longitudinal directions were measured and recorded as L1. The samples were transferred to an oven and baked at 150 °C for 30 min. After the samples cooled down, they were taken out, and the side lengths of the samples in the transverse and longitudinal directions were measured and recorded as L2. The thermal deformation rate of the samples was calculated. Thermal deformation rate = (L1 - L2) × 100% / L1.

[0134] 3. Test Results

[0135] The test results of this test example are shown in Table 1. The test objects of this test example are all carbon-coated current collectors with a carbon-coated layer on the surface of a polymer substrate. Among them, the carbon-coated layers of the carbon-coated current collectors prepared in Examples 1 to 15 all contain glass fiber reinforcing materials and carbon fiber reinforcing materials. Based on the excellent mechanical strength of glass fibers and the excellent electrical conductivity of carbon fibers, the two are combined to jointly participate in the construction of the carbon-coated layer, which can improve the toughness of the carbon-coated layer on the premise of maintaining good electrical conductivity of the carbon-coated layer, and then improve the structural stability of the carbon-coated current collector; in addition, glass fibers are sensitive to humidity and are prone to corrosion and degradation in a high-humidity environment. In Examples 1 to 15, by using carbon fibers and glass fibers in combination, the sensitivity of glass fibers to humidity can be effectively reduced, so that the carbon-coated current collector provided by this solution has good moisture resistance. In the data shown in Table 1, compared with the carbon-coated current collectors prepared in Comparative Examples 1 to 4, the carbon-coated current collectors provided in Examples 1 to 15 have lower elongation rates, humidity sensitivity rates, and heat deformation rates. This shows that the carbon-coated current collectors prepared in the examples have good structural stability and resistance to heat and humidity.

[0136] Taking Example 1 as a comparison, by changing the types of fiber reinforcing materials contained in the carbon-coated layer of the carbon-coated current collector, Comparative Examples 1 to 3 were set up. Specifically, the carbon-coated slurries prepared in Comparative Example 1 do not contain glass fibers and carbon fibers, the carbon-coated slurries prepared in Comparative Example 2 do not contain glass fibers, and the carbon-coated slurries prepared in Comparative Example 3 do not contain carbon fibers. Compared with the carbon-coated current collector prepared in Example 1, the comprehensive performance of the carbon-coated current collectors prepared in Comparative Examples 1 to 3 is significantly worse. Among them, only glass fibers are used as the reinforcing material in the carbon-coated slurry prepared in Comparative Example 3. As mentioned above, glass fibers are relatively sensitive to humidity. Based on this, the humidity sensitivity rate measured for the carbon-coated current collector prepared in Comparative Example 3 is significantly higher. Compared with Comparative Example 3, Comparative Example 2 uses carbon fiber reinforcing materials to participate in the construction of the carbon-coated layer of the carbon-coated current collector. Although it can reduce the humidity sensitivity rate of the carbon-coated current collector to a certain extent, the effect is not obvious, and the humidity sensitivity rate measured for the carbon-coated current collector prepared in Comparative Example 2 is still relatively high. However, compared with Comparative Examples 2 and 3, in Example 1, carbon fiber reinforcing materials and glass fiber reinforcing materials are used in combination to jointly construct the carbon-coated layer of the carbon-coated current collector, and the two work synergistically, which can significantly reduce the humidity sensitivity rate of the carbon-coated current collector.

[0137] Examples 1 to 3 and Comparative Example 4 were compared. Through conversion, in the process of preparing the carbon-coated current collector, the mass ratio of carbon fiber to glass fiber in the reinforcing fiber ratio used in Example 1 was 8, the mass ratio of carbon fiber to glass fiber in the reinforcing fiber ratio used in Example 2 was 4, the mass ratio of carbon fiber to glass fiber in the reinforcing fiber ratio used in Example 3 was 6, and the mass ratio of carbon fiber to glass fiber in the reinforcing fiber ratio used in Comparative Example 4 was 2. By comparing the test results of the carbon-coated current collectors prepared in Examples 1 to 3 and Comparative Example 4 respectively, it can be found that as the mass ratio of carbon fiber to glass fiber increases, the comprehensive performance of the carbon-coated current collector becomes better. When the mass ratio of carbon fiber to glass fiber is less than 4 (Comparative Example 4), the comprehensive performance of the carbon-coated current collector is significantly poor.

[0138] Although the carbon-coated layer of the carbon-coated current collector prepared in Comparative Example 5 contains both glass fiber and carbon fiber, when comparing the test results of the carbon-coated current collector prepared in Comparative Example 5 with that in Example 1, the comprehensive performance of the carbon-coated current collector prepared in Comparative Example 4 is significantly insufficient. This is because in the process of preparing the carbon-coated current collector in Comparative Example 5, the applied reinforcing fiber was not compounded with the resin material to prepare the fiber-reinforced material, but the reinforcing fiber was directly added to the slurry during the preparation of the carbon-coated slurry. Due to the lack of protection of the resin material, it is difficult for the reinforcing fiber to fully play its role under the influence of external factors such as high temperature and high humidity. In particular, the reinforcing fiber itself is difficult to help inhibit the thermodynamic deformation of the carbon-coated current collector. By compounding the reinforcing fiber with the resin material, on the one hand, the resin material can protect the reinforcing material, and on the other hand, it can effectively reduce the deformation problem caused by the thermodynamic residual stress to the material, so that the moisture and heat resistance of the carbon-coated current collector is significantly improved.

[0139] Furthermore, Example 1 was compared with Examples 9 to 11. On the premise of using polymer substrates of the same specification, the mass of glass fiber and the mass of carbon fiber contained in the carbon-coated current collectors prepared in the above examples are equal, but there are still certain differences in the product performance of the carbon-coated current collectors prepared in the above examples. The reason is that there are differences in the ratio of the reinforcing fiber to the resin material in the fiber-reinforced materials used in the above examples. By comparing the test results of the carbon-coated current collectors prepared in the above examples in this test example, it can be seen that for the carbon-coated current collector containing the fiber-reinforced material in the carbon-coated layer, by selecting a fiber-reinforced material with a mass ratio of the resin material to the reinforcing fiber not less than 2, the comprehensive performance of the carbon-coated current collector can be further improved.

[0140] The carbon coating layer of the carbon-coated current collector provided in Example 4 is thinner than that of the carbon-coated current collector provided in Example 1. It can be seen from the test results that the carbon-coated current collector of Example 1 has better structural stability and heat and temperature resistance. Nevertheless, the comprehensive performance of the carbon-coated current collector provided in Example 4 is still significantly better than the comprehensive performance of each of the carbon-coated current collectors provided in Comparative Examples 1-5.

[0141] In Examples 12 and 13, polyester resin and acrylic resin were respectively used as the resin materials for compounding with the reinforcing fibers. Combining with Example 1 (the resin material used was epoxy vinyl resin), it can be seen that using epoxy vinyl resin and polyester resin as the resin materials adopted in this solution is beneficial to improving the carbon-coated current collector to obtain better heat and temperature resistance.

[0142] Comparing Example 1 with Examples 5-8 can reflect the different effects of the differences between the preparation processes of the fiber reinforcing materials on the product performance of the carbon-coated current collector.

[0143] Comparing Example 1 with Example 5, in the process of preparing the fiber reinforcing material in Example 5, the low-temperature treatment of the premix formed by the reinforcing fibers and the resin material was omitted, which led to a relatively obvious increase in the elongation rate of the finally prepared carbon-coated current collector, indicating that the ability of the carbon-coated current collector to resist external forces became worse. This shows that in the process of preparing the fiber reinforcing material, performing low-temperature treatment on the premix formed by mixing the reinforcing fibers and the resin material is beneficial to reducing the degree of deformation of the carbon-coated current collector due to external forces and improving the structural stability of the carbon-coated current collector. Based on the above low-temperature treatment: it can reduce the adhesiveness of the resin material, improve the wettability performance of the carbon fiber, improve the bonding strength between the reinforcing fibers and the resin material, and thus improve the mechanical stability of the carbon-coated current collector, including improving strength and stiffness, etc., avoiding damage during the processing process, and also reducing the occurrence of deformation and warping of the carbon-coated current collector; it can reduce the fluidity of the resin material, thereby improving the controllability of the carbon coating layer processing, improving the quality stability of the carbon coating layer, and increasing the yield of high-quality products. If the fluidity of the resin material is too high, during the process of preparing the carbon-coated current collector, the processing controllability of the fiber reinforcing material containing the resin material is poor, and it is easy to cause structural defects in the carbon coating layer.

[0144] Compared to Example 1, Examples 6-8 differed in the pretreatment procedures applied to the reinforcing fibers before using them to make fiber-reinforced materials. In Example 1, the carbon fibers and glass fibers were subjected to the SO pretreatment described in Example 1, serving as a reference. This pretreatment procedure was omitted in Example 6. Examples 7 and 8 both performed the corresponding pretreatment procedures on the reinforcing fibers, but the pretreatment temperature for the glass fibers in Example 7 was higher, while the pretreatment temperature for the carbon fibers in Example 8 was lower. Judging from the test results, based on the difference in pretreatment operations, the product performance of the carbon-coated current collectors prepared in Example 1 and Examples 6 to 8 respectively constitutes a certain difference. Generally speaking, before preparing the fiber-reinforced material, the glass fiber is pretreated and heated at 400°C to 600°C, and the carbon fiber is pretreated and heated at 700°C to 900°C. This can reduce the toughness of the reinforcing fiber to a certain extent, thereby achieving the effect of promoting the uniform mixing of the reinforcing fiber and the resin material. At the same time, the toughness of the reinforcing fiber is not significantly reduced. The reinforcing fiber can still optimize the structural stability of the carbon-coated current collector, thereby further improving the comprehensive performance of the carbon-coated current collector.

[0145] Comparing Example 1 with Examples 14 and 15 reveals the varying effects that differences in the carbon-coated slurry preparation process have on the product performance of the carbon-coated current collector. In Example 1, during the preparation of the carbon-coated slurry, the conductive agent was added in two stages, while the glass fiber and carbon fiber were added to the slurry sequentially, before and after the addition of the conductive agent. This allowed the two different reinforcing fibers to be evenly interspersed within the conductive agent, improving the dispersion of the carbon-coated slurry. Among the carbon-coated slurries prepared in the aforementioned examples, the one prepared in Example 1 exhibited the best uniformity and coating performance.

[0146] Table 1. Test result statistics of this test case

[0147]

[0148] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents, but these modifications or replacements are all within the scope of protection of the present invention.

Claims

1. A carbon-coated current collector, characterized in that: The carbon-coated current collector includes a conductive substrate and a carbon-coated layer; The carbon-coated layer includes a conductive agent and a fiber reinforcing material, and the percentage of the mass of the fiber reinforcing material in the mass of the conductive agent is 5% to 30%; The fiber reinforcing material includes reinforcing fibers and a resin material, and the reinforcing fibers include glass fibers and carbon fibers; The mass of the carbon fiber: the mass of the glass fiber ≥ 4; The percentage of the mass of the glass fiber in the mass of the conductive agent is 0.2% to 5%; The preparation of the fiber reinforcing material includes the following steps: S1. Mix the reinforcing fibers and the resin material in proportion to obtain a premix; S2. Perform cryogenic treatment on the premix, and the treatment temperature of the cryogenic treatment is -210°C to -190°C; S3. Heat the premix to cure the resin material, thereby obtaining the fiber reinforcing material; The fiber reinforcing material includes a glass fiber reinforcing material and a carbon fiber reinforcing material. The reinforcing fibers contained in the glass fiber reinforcing material are the glass fibers, and the reinforcing fibers contained in the carbon fiber reinforcing material are the carbon fibers; in the glass fiber reinforcing material, the mass of the resin material: the mass of the glass fiber ≥ 2; in the carbon fiber reinforcing material, the mass of the resin material: the mass of the carbon fiber ≥ 2.

2. The carbon-coated current collector according to claim 1, characterized in that: The conductive agent includes at least one of graphite and carbon black.

3. The carbon-coated current collector according to claim 1, characterized in that: The thickness of the conductive substrate is 8μm to 12μm.

4. The carbon-coated current collector according to claim 1, characterized in that In the process of preparing the fiber reinforcing material, before the S1, a pretreatment of the reinforcing fibers is further included, and the pretreatment includes the following operations: performing a heat treatment on the reinforcing fibers, and the temperature of the heat treatment is 400°C to 900°C.

5. The carbon-coated current collector according to claim 1, wherein: The resin material includes at least one of an epoxy resin material, a polyester resin material, and an acrylic resin material.

6. The carbon-coated current collector according to claim 5, wherein The carbon-coated current collector satisfies at least one of the following a and b: a. The glass fiber includes fibers with a length reaching 10 mm or more, and the resin material contained in the glass fiber reinforcing material includes at least one of an epoxy resin material and a polyester resin material; b. The carbon fiber includes fibers with a length reaching 10 mm or more, and the resin material contained in the carbon fiber reinforcing material includes at least one of an epoxy resin material and a polyester resin material.

7. A method for preparing the carbon-coated current collector according to any one of claims 1 to 6, characterized in that: It includes the following operations: preparing a carbon-coated slurry, and coating the carbon-coated slurry on the surface of the conductive substrate to form the carbon-coated layer on the surface of the conductive substrate; In the process of preparing the carbon-coated slurry, the feeding order of the conductive agent and the fiber reinforcing material is as follows: first, part of the conductive agent is added to the glue containing the binder, then the glass fiber reinforcing material is added, and then the remaining conductive agent is added. After the addition of the conductive agent is completed, the carbon fiber reinforcing material is added.

8. A secondary battery, characterized in that: The secondary battery includes the carbon-coated current collector according to any one of claims 1 to 6.

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