Lithium-ion battery electrode sheet and preparation method thereof

Abstract

The present invention discloses a lithium-ion battery electrode plate and a preparation method thereof, and belongs to the field of lithium-ion batteries. The present invention mixes a film-forming agent with an active substance, applies it to the electrode plate, and then performs a carbonization treatment to construct a carbon-coated particle electrode plate structure without an organic binder. The carbonization process is introduced into the electrode plate preparation process, and the organic binder is carbonized at high temperature to form a carbon coating layer and chemical bonding on the plate. The carbon coating layer acts as a binder and a conductive agent at the same time, improving the interface stability and electron transport of the electrode plate. It can also maintain good electron and ion transport properties when the electrode volume changes during the charge and discharge process, improve the structural stability of the electrode, reduce the expansion rate, improve the first coulomb efficiency of the battery, and improve the cycle stability, rate performance and low temperature performance. The electrode plate can be applied to the negative electrode of a secondary battery and has great market potential.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and in particular to a lithium-ion battery electrode plate and a preparation method thereof. Background Art

[0002] The growing market for portable electronic devices and electric vehicles has had a significant impact on the development of higher energy density secondary battery technology.

[0003] The performance of battery components and their manufacturing processes fundamentally determine the overall performance of a battery. Compared to materials, optimizing electrode preparation offers significant advantages, as it determines the performance of active materials, especially for thicker electrodes.

[0004] The pole piece design includes the optimization of the current collector, conductive agent, adhesive, etc. and the design of flexible electrodes. The optimization of the current collector mainly focuses on: first, making the current collector thinner to reduce the proportion of inactive substances; second, designing microstructures on the current collector to enhance the connection with active substances. Both of the above-mentioned current collector optimizations have problems such as high manufacturing costs and complex processes. The main purpose of optimizing the conductive agent is to improve the electron and ion transport properties of the pole piece. Currently, the conductive agents with better effects are graphene and carbon nanotubes, but they are limited by cost and the complexity of pole piece preparation. Flexible electrode design can achieve excellent electrochemical performance in button batteries, especially in terms of surface capacity, reflecting ultra-high energy density, but the problem that it is difficult to weld the tabs of flexible electrodes restricts its application in practice.

[0005] Compared with the first two types of electrode optimization and flexible electrode design, designing a suitable binder is the most promising optimization solution. Among them, binders with excellent electron and ion transport properties can not only act as binders, but also eliminate the need to add conductive agents to the electrode, thereby increasing the proportion of active materials in the electrode, thereby improving the energy density of the battery. However, the production cost of such binders currently reported is high and the process is complex, which restricts their large-scale application. In addition, because most binders are organic, the electrode has a high electrolytic swelling rate, and the active material is also prone to expansion during the electrochemical process, which makes its safety of use worrying. Therefore, it is necessary to explore new electrode preparation processes to replace the use of conductive binders. Summary of the Invention

[0006] The main purpose of the present invention is to provide a lithium-ion battery electrode plate and its preparation method, which aims to prepare a lithium-ion battery electrode plate containing an active material 1 carbon composite structure through a carbonization process, replacing the electrode plate using a conductive binder, and solving technical problems such as poor stability of the electrode plate, unsatisfactory electron and ion transmission performance, high expansion rate, and safety performance that needs to be improved.

[0007] To achieve the above-mentioned objectives, the present invention provides a lithium-ion battery electrode plate, which includes an active material, a current collector and a carbon coating layer coated on the active material and the current collector, and does not contain organic matter. The active material is a negative electrode material, and the negative electrode material includes at least one of graphite, hard carbon, silicon dioxide and silicon.

[0008] Optionally, the compacted density of the lithium-ion battery electrode plate is 1.0 g c1 -3 ≤ρ≤5.0g c1 -3 , single surface density is 1~200 1g c1 -2 , thickness is 20~1000μ1, specific surface area increase ≤100 1 2 g -1 .

[0009] In addition, to achieve the above-mentioned object, the present invention also provides a method for preparing a lithium-ion battery electrode sheet, the preparation method comprising the following steps:

[0010] S10, mixing the active material and the film-forming agent, stirring them uniformly to obtain a viscous mixture, coating the viscous mixture on the surface of the current collector, and then drying to obtain an initial negative electrode sheet;

[0011] S20, heating the initial negative electrode sheet to prepare a lithium-ion battery electrode sheet;

[0012] Wherein, the active material is a negative electrode material, and the negative electrode material includes at least one of graphite, hard carbon, silicon monoxide and silicon.

[0013] Optionally, the weight ratio of the active substance to the film-forming agent is 0.5:9.5 to 9.5:0.5.

[0014] Optionally, in the step of mixing and uniformly stirring the active substance and the film-forming agent, the stirring temperature is 10 to 200° C. and the stirring time is 1 to 24 hours.

[0015] Optionally, the current collector is at least one of copper foil, steel foil, and titanium foil.

[0016] Further optionally, the current collector is copper foil.

[0017] Optionally, in the step of heat-treating the initial negative electrode sheet, the heat-treating is performed in an inert gas atmosphere, and the inert gas atmosphere is at least one of nitrogen, argon, and an argon-hydrogen mixture.

[0018] Optionally, the temperature of the heating treatment is 250-1500° C., the heating rate is 1-10° C., and the holding time is 0-24 h.

[0019] Optionally, the prepared lithium-ion battery electrode plate is subjected to secondary carbon coating.

[0020] Optionally, the lithium-ion battery electrode plate is subjected to a secondary carbon coating by a vapor deposition method.

[0021] Optionally, the temperature of the vapor deposition method is 600-1200° C., and the holding time is 0.5-24 h.

[0022] Optionally, the viscosity of the viscous mixture is 1000-8000 1Pa·s.

[0023] Optionally, the active material particles D50 are 1 to 30 μl.

[0024] Optionally, the viscosity of the viscous mixture is 1000-8000 1Pa·s.

[0025] Optionally, the film-forming agent includes starch, starch derivatives, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyethyleneimine, polymaleic anhydride, polyquaternary ammonium salt, hydrolyzed polyacrylamide, natural plant gum, polyethylene oxide, ionic water-soluble epoxy resin, ionic maleic anhydride polybutadiene resin, cationic water-soluble polychloride resin, water-based asphalt emulsion, water-based epoxy resin, water-based polyacrylate, sodium carboxymethyl cellulose, sodium carboxymethyl starch, polyvinyl alcohol, sodium polystyrene sulfonate, polydopamine, polyethylene glycol, water-based polyurethane, polyacrylic acid, guar gum, chitosan, gelatin, sodium alginate, polyvinyl pyrrolidone, xanthan gum, calcium alginate, gellan gum, cyclodextrin, karaya gum, gum arabic and derivatives thereof.

[0026] The beneficial effects that can be achieved by the present invention are:

[0027] The present invention provides a lithium-ion battery electrode plate, comprising an active material, a carbon coating layer, and a current collector. The carbon coating layer not only functions as a conductive agent, but also acts as a binder because it forms a bond with the active material and the current collector under high temperature conditions. The carbon coating layer has a strong interfacial bonding force with each other, which limits the expansion of the active material during the electrochemical process. This can effectively alleviate volume expansion while ensuring that the electrode structure is not damaged, thereby reducing the expansion rate of the electrode plate. In addition, because the electrode plate does not contain organic matter, the electrolyte swelling rate is almost zero, while the electrolytic swelling rate of traditional negative electrode plates is as high as 50%. The low electrode swelling rate and low electrolyte swelling rate can improve the safety of use and electrochemical performance.

[0028] When applied to batteries, these lithium-ion battery electrode sheets can provide the batteries with low-temperature performance, high energy density, high initial coulombic efficiency, and excellent cycling stability. Furthermore, due to the excellent electron and ion transport properties of the carbon coating, ultra-thick electrode sheets with thicknesses exceeding 300μl can be designed, further reducing the proportion of inactive components, thereby increasing the battery's energy density and reducing costs.

[0029] The electrode preparation method disclosed in the present invention is simple and easy, pollution-free, safe and reliable, low-cost, more universally applicable, and more efficient. It can realize industrial mass production without adding conductive agents, reducing process complexity and manufacturing costs, reducing the proportion of low-1 inactive substances in the electrode, and easily producing high-pressure solid electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0031] Figure 1 This is a process flow chart of a method for preparing a lithium-ion battery electrode sheet according to Examples 1 to 4 of the present invention.

[0032] Figure 2 This is a process flow chart of a method for preparing a lithium-ion battery electrode sheet according to Example 5 of the present invention.

[0033] Figure 3 This is a surface scanning electron microscope image of the lithium-ion battery electrode sheet in Example 1 of the present invention.

[0034] Figure 4 This is a cross-sectional scanning electron microscope backscattered electron image of a lithium-ion battery electrode sheet after being cut using a focused ion beam in Example 1 of the present invention.

[0035] Figure 5 This is the first charge and discharge curve of the lithium-ion battery electrode sheet in Example 1 of the present invention at a current density of 0.033C (1C=3579 1A1g).

[0036] Figure 6 1 is a cycle performance diagram of the lithium-ion battery electrode sheet in Example 1 of the present invention at a current density of 0.033C (1C=3579 1A1g).

[0037] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0038] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] In the present invention, descriptions such as "first" and "second" are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions of various embodiments may be combined with each other, but this must be based on the fact that they can be implemented by a person of ordinary skill in the art. If the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0041] The present invention provides a lithium-ion battery electrode plate, which includes an active material, a current collector, and a carbon coating layer coated on the active material and the current collector, and does not contain organic matter. The active material is a negative electrode material, and the negative electrode material includes at least one of graphite, hard carbon, silicon dioxide and silicon. The carbon coating layer can simultaneously serve as a binder and a conductive agent for the electrode plate.

[0042] The compaction density of the lithium-ion battery electrode plate is 1.0gc1 -3 ≤ρ≤5.0gc1 -3 , single surface density is 1~2001gc1 -2 , thickness is 20~1000μ1, specific surface area increase ≤1001 2 g -1 .

[0043] The present invention also provides a method for preparing the above-mentioned lithium-ion battery electrode sheet. In one embodiment, referring to Figure 1 , the preparation method comprises the following steps:

[0044] S10, mixing the active material and the film-forming agent, stirring them uniformly to obtain a viscous mixture, coating the viscous mixture on the surface of the current collector, and then drying to obtain an initial negative electrode sheet.

[0045] The film-forming agent includes a water-soluble polymer, but is not limited to a water-soluble polymer. Preferably, the film-forming agent includes starch, starch derivatives, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyethyleneimine, polymaleic anhydride, polyquaternary ammonium salt, hydrolyzed polyacrylamide, natural plant gum, polyethylene oxide, ionic water-soluble epoxy resin, ionic maleic anhydride polybutadiene resin, cationic water-soluble polychloride resin, aqueous asphalt emulsion, aqueous epoxy resin, aqueous polyacrylate, sodium carboxymethyl cellulose, sodium carboxymethyl starch, polyvinyl alcohol, sodium polystyrene sulfonate, polydopamine, polyethylene glycol, aqueous polyurethane, polyacrylic acid, guar gum, chitosan, gelatin, sodium alginate, polyvinyl pyrrolidone, xanthan gum, calcium alginate, gellan gum, cyclodextrin, karaya gum, gum arabic and one or more of its derivatives.

[0046] The present invention does not limit the weight ratio of the active substance to the film-forming agent. Preferably, the weight ratio of the active substance to the film-forming agent is 0.5:9.5 to 9.5:0.5. In some embodiments, the D50 of the active substance is 1 to 30 μl and the specific surface area is 1 to 101. 2 g -1 In some embodiments, the temperature for mixing and stirring the active substance and the film-forming agent is preferably 10 to 200° C., and the stirring time is preferably 1 to 24 hours. Under the above preferred conditions, the active substance and the film-forming agent can be mixed more evenly, which can also promote the subsequent carbonization reaction.

[0047] In this embodiment, the film-forming agent can be understood as a binder. When the film-forming agent is a water-soluble polymer, the water-soluble polymer can be first dissolved in a mixed solution of deionized water and alcohol, and then the active substance is added. This can avoid uneven dispersion of the active substance and the film-forming agent, which in turn affects the electrochemical properties of the carbon coating layer.

[0048] Furthermore, the viscosity of the viscous mixture is preferably between 1000 and 8000 1Pa·s. A viscosity within this range can enhance the adhesion of the viscous mixture to the current collector, preventing the viscous mixture from falling off due to insufficient viscosity during the high-temperature carbonization process, which would affect the effectiveness of the carbon coating layer as a binder in the finished product.

[0049] The present invention does not limit the type of the current collector, which is preferably at least one of copper foil, steel foil, and titanium foil. Furthermore, the current collector is copper foil.

[0050] S20, heating the initial negative electrode sheet to prepare a lithium-ion battery electrode sheet.

[0051] Specifically, the heat treatment is performed in an inert gas atmosphere, and the inert gas atmosphere is at least one of nitrogen, argon, and an argon-hydrogen mixed gas.

[0052] The temperature of the heat treatment in this step is preferably 250-1500°C, the heating rate is preferably 1-10°C, and the holding time is 0-24h. Keeping the carbonization temperature rising slowly can prevent the viscous mixture from being heated unevenly due to an instantaneous temperature increase, resulting in cracks in the carbon coating and pulverization of the active material particles. In addition, it should be noted that the holding time is calculated from the start of heating to a stable temperature. The holding time of 0-24h can be understood as: either a heat preservation treatment can be performed or not, and heat preservation treatment can further improve the electrochemical stability of the carbon coating.

[0053] The present invention introduces a heat treatment process into the electrode preparation process, forms an active material 1 carbon composite structure on the electrode, and constructs an integrated electrode, which can greatly improve the electron and ion transport properties of the electrode, thereby obtaining a negative electrode with high first coulombic efficiency and long cycle stability.

[0054] The carbon composite structure of the active material 1 of the lithium-ion battery electrode plate is different from the carbon coating of a single particle active material. Instead, a composite material with the active material as the reinforcing phase and the carbon coating layer as the matrix is ​​formed on the current collector. There is a strong constraint between the particles, that is, there is a strong chemical bond between the carbon coating layer and the active material particles, and between the carbon coating layer and the current collector. This allows the carbon coating layer to serve as both a binder and a conductor for the electrode plate, making it more adaptable to the volume changes of the active material and controlling the expansion degree of the active material during the electrochemical process. It can effectively prevent the carbon coating layer from rupturing and the active material particles from pulverizing, ensuring that the conductive environment formed is not destroyed, thereby reducing the expansion rate of the electrode plate. In addition, because the electrode plate does not contain organic matter, the electrolyte swelling rate is almost zero, while the electrolytic swelling rate of traditional negative electrode plates is as high as 50%. The low electrode swelling rate and low electrolyte swelling rate can improve safety in use and electrochemical performance.

[0055] In addition, because it does not contain organic matter and has extremely low water content, the electrode plates can have the characteristics of high thermal conductivity, non-flammability and high safety performance.

[0056] In which, the current collector forms a bonding effect with the carbon coating layer under a high temperature environment, and the bonding effect includes but is not limited to at least one of CO-Cu, CO-Fe and CO-T1 bonds; the active material forms a bonding effect with the carbon coating layer under a high temperature environment, and the bonding effect includes but is not limited to one or more of COC, CO-S1 and C-S1.

[0057] In another embodiment, referring to Figure 2 The preparation method further includes performing secondary carbon coating on the lithium-ion battery electrode plate.

[0058] Specifically, a carbon-containing process gas is introduced under a protective atmosphere to vapor-deposit carbon, thereby subjecting the electrode sheet to a secondary carbon coating. The protective atmosphere is at least one of nitrogen, argon, and an argon-hydrogen mixture. The carbon-containing process gas is one of a C1-4 alkane, a C2-4 olefin, or a C2-4 alkyne. This secondary carbon coating further improves the mechanical and electrochemical stability of the electrode sheet.

[0059] The compaction density of the lithium ion battery electrode plate prepared by the present invention is 1.0gc1 -3 ≤ρ≤5.0gc1 -3 , single surface density is 1~2001g c1 -2 , thickness is 20~1000μ1, specific surface area increase ≤1001 2 g -1 .

[0060] The technical solutions of the present invention are further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not used to limit the present invention.

[0061] Example 1

[0062] Reference Figure 1 The method for preparing a lithium-ion battery electrode sheet comprises the following steps:

[0063] In step S10, 200 μg of soluble starch was weighed and dissolved in deionized water. The mixture was stirred in an 80°C water bath for 0.5 h. Then, 200 μg of 5μl silicon powder was added and stirred at 10°C for 1 h to obtain a viscous mixture. The viscous mixture was evenly coated on a 10μl steel foil and dried to obtain the initial electrode.

[0064] S20, after punching the initial electrode sheet of S10 into a button battery electrode sheet with a diameter of 1211, it is moved to a tubular furnace for heat treatment. The carbonization procedure is: heating from 10℃ to 1500℃, keeping the temperature for 0.5h, to obtain a lithium-ion battery electrode sheet.

[0065] In this embodiment, the lithium-ion battery electrode plate is a micron silicon-based lithium-ion battery electrode plate, which can be directly used as a working plate for the assembly of button batteries. The active material includes silicon and carbon.

[0066] The micron silicon-based lithium-ion battery electrode obtained in Example 1 was characterized using a scanning electron microscope. The results are as follows: Figure 3 As shown: A layer of starch carbon is evenly deposited near the micron silicon particles on the micron silicon-based lithium-ion battery electrode.

[0067] After the micron silicon-based lithium-ion battery electrode sheet is cut using a focused ion beam, the exposed cross section is characterized using a scanning electron microscope to obtain a scanning electron microscope backscattered electron image, such as Figure 4 As shown: After carbonization, the electrode forms a good electron and ion transport network.

[0068] Example 2

[0069] Reference Figure 1 The method for preparing a lithium-ion battery electrode sheet comprises the following steps:

[0070] S10, weigh 1901g of sodium carboxymethyl cellulose, dissolve it in a mixture of deionized water and alcohol, stir for 0.5h, then add 10.1g of silicon powder with a particle size of 3011, and stir at 25°C for 6h to obtain a viscous mixture, evenly coat the viscous mixture on a 10μ1 copper foil, and obtain the initial electrode after drying.

[0071] S20, after punching the initial electrode sheet of S10 into a button battery electrode sheet with a diameter of 1211, it is moved to a tubular furnace for heating and carbonization treatment. The carbonization treatment procedure is: heating to 500°C at 1°C / 1111 and keeping warm for 2 hours to obtain a lithium-ion battery electrode sheet.

[0072] In this embodiment, the lithium-ion battery electrode plate is a nano-silicon-based lithium-ion battery electrode plate, which can be directly used as a working plate for assembling button batteries, and the active material includes silicon and carbon.

[0073] Example 3

[0074] In this embodiment, referring to Figure 1 The method for preparing a lithium-ion battery electrode sheet comprises the following steps:

[0075] S10, weigh 2001g of ethyl cellulose, dissolve it in a mixture of deionized water and alcohol, and stir for 0.5h. Then add 6001g of graphite with a particle size of 12μl, and stir at 200℃ for 12h to obtain a viscous mixture. The viscous mixture is evenly coated on a 10μl titanium foil and dried to obtain the initial electrode.

[0076] S20, after punching the initial electrode sheet of S10 into a button battery electrode sheet with a diameter of 1211, it is moved to a tubular furnace for heating and carbonization treatment. The carbonization treatment procedure is: heating from 5°C to 250°C at 1111°C, keeping the temperature for 24 hours, and obtaining a lithium-ion battery electrode sheet.

[0077] In this embodiment, the lithium-ion battery electrode plate is an integrated graphite-based lithium-ion battery electrode plate, which can be directly used as a working plate for assembling button batteries, and the active material includes silicon and carbon.

[0078] Example 4

[0079] In this embodiment, referring to Figure 1 The method for preparing a lithium-ion battery electrode sheet comprises the following steps:

[0080] S10, weigh 501g of sodium carboxymethyl cellulose and put it into a weighing bottle, dissolve it in a mixture of deionized water and alcohol, stir for 0.5h, then add 4501g of graphite with a particle size of 12μ1 and 5001g of micron silicon with a particle size of 5μ1, stir at 30°C for 15h to obtain a viscous mixture, evenly coat the viscous mixture on a 10μ1 copper foil, and obtain the initial electrode after drying.

[0081] S20, after punching the initial electrode sheet of S10 into a button battery electrode sheet with a diameter of 1211, it is moved to a tubular furnace for heating and carbonization treatment. The carbonization treatment procedure is: heating from 1°C to 500°C to obtain a lithium-ion battery electrode sheet.

[0082] In this embodiment, the lithium-ion battery electrode plate is a silicon-graphite-based lithium-ion battery electrode plate, which can be directly used as a working plate for the assembly of button batteries. The active material includes silicon, graphite and carbon.

[0083] Example 5

[0084] Reference Figure 2 The preparation method of this embodiment is basically the same as the preparation method of Example 1, except that the lithium-ion battery electrode plate obtained in S20 is subjected to secondary carbon coating by vapor deposition: under a nitrogen protective atmosphere, C1-4 alkanes and C2-4 alkenes are introduced, and carbon elements are deposited at 1200°C for 24 hours to obtain a secondary carbon-coated lithium-ion battery electrode plate.

[0085] Comparative Example 1

[0086] The preparation method of Comparative Example 1 is the same as that of Example 1, except that the heating treatment in step S20 is not performed.

[0087] Performance Testing

[0088] Coin-type batteries were assembled using the electrode sheets obtained in Examples 1-5 and Comparative Example 1 as one of the electrodes and a metal lithium sheet as the counter electrode. The electrolyte was prepared by dissolving 1.0 M lithium hexafluorophosphate (L1PF6) in a 1:1 volume ratio of ethylene carbonate (EC) and diethyl carbonate (DEC), followed by the addition of 7.5% fluoroethylene carbonate (FEC) and 0.5% vinylene carbonate (VC) as the electrolyte.

[0089] 1. Setting the first cycle current density to 0.033C (1C = 35791A / g), all of the button cells described above were charged and discharged. The first charge specific capacity, first charge specific capacity, specific capacity after 50 cycles at a cycle current density of 0.33C, and capacity retention of the electrode sheets were measured. The results are shown in Table 1.

[0090] Table 1 Comparison of electrochemical properties of the electrode sheets obtained in Examples 1 to 5 and Comparative Example 1

[0091]

[0092]

[0093] 2. Under the conditions of the first cycle current density of 0.033C, 1C=3721A1g, and the rate retention rate based on 0.1C, the constant current ratios of the electrode sheets of Examples 1 to 5 and Comparative Example 1 were measured. The results are shown in Table 2.

[0094] Table 2 Comparison of electrochemical performance of the electrode sheets obtained in Examples 1 to 5 and Comparative Example 1

[0095]

[0096] Depend on Figure 5 、 Figure 6 As shown in Table 1, the first discharge specific capacity of the micron silicon-based lithium-ion battery electrode sheet of Example 1 is 3366.71Ah1g, the charge specific capacity is 3084.01Ah1g, and the first coulombic efficiency is as high as 91.6%. After 50 cycles at a current density of 0.33C, the capacity still maintains an ultra-high capacity of 2002.51Ah1g.

[0097] In addition, the electrode plates of Examples 2-5 all have high first coulombic efficiency and first charge specific capacity, and after 50 cycles, they also have high specific capacity and capacity retention rate.

[0098] The electrode plate of Comparative Example 1 did not go through the heating process, and its electrochemical performance was poor, with a capacity retention rate of almost zero after 50 cycles.

[0099] As can be seen from Table 2, the electrode prepared by this method has excellent rate performance and good electron and ion transport capability.

[0100] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a lithium-ion battery electrode sheet, characterized in that: The following steps are involved: The active material and the film-forming agent are mixed and stirred to obtain a viscous mixture, the viscous mixture is coated on the surface of the current collector, and then dried to obtain an initial negative electrode sheet; The initial negative electrode sheet is subjected to a heating treatment to prepare a lithium-ion battery electrode sheet; Performing secondary carbon coating on the lithium-ion battery electrode plate by vapor deposition; The temperature of the vapor deposition method is 600-1200°C, the holding time is 0.5-24h, and a carbon-containing process gas is introduced under a protective atmosphere to perform vapor deposition of carbon elements, and the electrode plates are subjected to secondary carbon coating. The protective atmosphere is at least one of nitrogen, argon, and argon-hydrogen mixed gas, and the carbon-containing process gas is C 1-4 Alkanes, C 2-4 Olefins, C 2-4 One of the alkynes; Wherein, the active material is a negative electrode material, and the negative electrode material includes at least one of graphite, hard carbon, silicon dioxide and silicon; The current collector is at least one of steel foil and titanium foil; The lithium-ion battery electrode plate includes the active material, the current collector, and a carbon coating layer coated on the active material and the current collector, and does not contain organic matter. The current collector forms a bond with the carbon coating layer, and the bond formed between the current collector and the carbon coating layer is one or more of CO-Fe and CO-Ti; The active substance forms a bond with the carbon coating layer, and the bond formed between the active substance and the carbon coating layer is one or more of COC, CO-Si and C-Si.

2. The method for preparing a lithium-ion battery electrode sheet according to claim 1, wherein: The weight ratio of the active substance to the film-forming agent is 0.5:9.5 to 9.5:0.

5.

3. The method for preparing a lithium-ion battery electrode sheet according to claim 1, wherein: In the step of mixing and uniformly stirring the active substance and the film-forming agent, the stirring temperature is 10 to 200° C. and the stirring time is 1 to 24 hours.

4. The method for preparing a lithium-ion battery electrode sheet according to claim 1, wherein: The current collector is at least one of copper foil, steel foil and titanium foil.

5. The method for preparing a lithium-ion battery electrode sheet according to claim 1, wherein: In the step of heat-treating the initial negative electrode sheet, the heat-treating is performed in an inert gas atmosphere, and the inert gas atmosphere is at least one of nitrogen, argon, and an argon-hydrogen mixed gas.

6. The method for preparing a lithium-ion battery electrode sheet according to claim 1, wherein: The temperature of the heating treatment is 250-1500° C., the heating rate is 1-10° C., and the holding time is 0-24 hours.

7. The method for preparing a lithium-ion battery electrode sheet according to claim 1, wherein: The film-forming agent includes one or more of starch, starch derivatives, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyethyleneimine, polymaleic anhydride, polyquaternary ammonium salt, hydrolyzed polyacrylamide, natural plant gum, polyethylene oxide, ionic water-soluble epoxy resin, ionic maleic anhydride polybutadiene resin, cationic water-soluble polychloride resin, water-based asphalt emulsion, water-based epoxy resin, water-based polyacrylate, sodium carboxymethyl cellulose, sodium carboxymethyl starch, polyvinyl alcohol, sodium polystyrene sulfonate, polydopamine, polyethylene glycol, water-based polyurethane, polyacrylic acid, guar gum, chitosan, gelatin, sodium alginate, polyvinyl pyrrolidone, xanthan gum, calcium alginate, gellan gum, cyclodextrin, karaya gum, gum arabic and derivatives thereof.

8. A lithium-ion battery electrode sheet prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The lithium-ion battery electrode plate includes an active material, a current collector, and a carbon coating layer coated on the active material and the current collector, and does not contain organic matter. The active material is a negative electrode material, and the negative electrode material includes at least one of graphite, hard carbon, silicon dioxide, and silicon.

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